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    • #34011
      Goodsteel
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      Every now and then, a precision rifle will exhibit a strange phenomenon, in which the cone of fire will shift positions range session to range session. I noticed this with my 300 winmag before, but since I was shooting 3 and 5 shot groups back then, I assumed I was merely being taken in by shooting too small a sample size and I was merely chasing my POI.
      However, I have now seen this phenomenon exhibited in ten shot groups, and I’m back to scratching my head.
      The rifle I am working with now is one I built for Bjornb in 6x45mm. It has a Krieger barrel and has a cone of fire of 3/4″ at 100 yards with the load I am using.
      Three times now, I have set up and fired at least four ten shot groups. I shoot two groups (20 shots) wonder why the center of my group is not spot on, adjust the scope into the center of the group, then shoot two more groups to satisfy myself its right on.

      The next outing is a repeat of this performance.

      Just today, I had a prospective client in the shop and I pulled out the 6×45 to give him a demonstration. He shot a beautiful 5/8″ group for five shots, but I noticed it was 1″ high and 3/4″ left of his aim point. He was duly impressed with the precision of the rifle, but as soon as he left, I sat down and shot another ten shots into a group, and was frustrated to find my group was off an identical amount as the previous one shot by my visitor (it bears mentioning that the rifle lay right there on the bags for an hour or more while my business with my client was concluded).
      I made yet another adjustment to the scope (Vortex Viper) and it tracked perfectly with ever click as usual.

      I have suspected this was happening on other occasions, but now I am certain. This effectively makes the reliable cone of fire of a subMOA rifle more like 2MOA or more, and that bugs me. This rifle has no tendancy for a first shot flier, and if I can solve this frustrating and minute problem, I can shoot the head off a turkey buzzard at 100 yards, and I want to be able to do so.

      Have any of you been in a position where precision and accuracy have been brought together on demand? Do you know what it is I am seeing here?

    • #34013
      slim1836
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      Could it be so simple as your cheek weld has changed?

      Slim

    • #34015
      Scharfschuetze
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      I have no idea and can only guess that it’s the vagaries of the shooting Gods. Is there perhaps a humidity issue and a wood stock involved?

      On the other hand, that definitely proves the old advice to always check your zero before starting a hunt.

      It also reminds me of the saga of the Mk V No I Jungle Carbine and it’s claimed wondering zero.

    • #34016
      Goodsteel
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      Without snapping my suspenders too loudly…..very unlikely.

    • #34017
      kens
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      Differences in temperature, humidity, powder sensitive to temps, dissimilar metals??
      wind drift? you using wind flags?
      What if you had a aluminum scope tube in steel rings, on a steel receiver?
      Does the alum tube expand & contract just like the rings & receiver?
      Does alum tube get hot, expand in steel rings, and get tight? (tighter)
      Do alum tube get cold and contract in steel rings (get looser)
      Does the receiver get hot and grow longer, (scope is constant)

      The more accurate you try to do something, the more variables that come into play.

    • #34018
      Goodsteel
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      Well please do keep in mind, I’m not talking about a huge change here. I’m talking about a 1″ change in POI. Unless you were hunting field mice at 100 yards. It just agrivates me to take a rifle capable of ten shits into less than an inch, and not be able to call my shot on a 1″ target cold turkey. Besides, its a weird phenomenon and I don’t understand it.

      Yes, its a laminated stock. But its completely free floated, and has contact only with the action, and has no influence on the barrel or the scope. I cannot see how it could effect the relationship between the two. Not that I’m opposed to the idea you understand. I just don’t see how it is possible.

    • #34020
      Sgt. Mike
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      Tim,
      stupid idea says put another scope on and see if it holds zero. Not knocking the Vortex. But the good part in changing the scope is it allows you to inspect everything again.
      Just a thought.

      the common denominator between the 6X45 and the 300 win mag is the scope. Scopes have been known to not hold zero yet track.

    • #34022
      JRR
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      I would check the torque on the action screws at the end of the shooting session. Check again before shooting on the next session. Assuming it will be on a different day. Perhaps the screws went to yoga class between sessions.

      Same batch of ammo loaded at the same sit down?

      By the way, the 6.5 you built for me has not changed more than .5″ at 100yrds, no matter what the bullet or powder used.

      Jeff

    • #34023
      Goodsteel
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      There is no common denominator. The 300 had two Leupolds, and the Vortex in the time I had it. I burned out a barrel in that rifle long before I built it into the rifle you know.
      I have seen this several times with several different rifles. In fact, every time I’ve had one that exhibited predictable precision and accuracy.

    • #34025
      Goodsteel
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      This is possible, but I know a great deal about thermal coefficients of expansion. If this were true, then all aluminum scopes would.
      And that’s all I’m wondering about. I wonder if those of you who ruetinely shoot small groups can tell me if you have seen this?

    • #34028
      Sgt. Mike
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      Well heck ya didn’t say it was before you rebarreled the 300 win mag thought it was after. 🙂

    • #34029
      Sgt. Mike
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      Well Heck you didn’t specify it was after you Rebarreled the 300 win mag. Thought you was referring to after the rebarreling 😉

    • #34030
      ZmanWakeForest
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      Why is there no “Like” icon on the comments made to a reply……that made me LOL Goodsteel!

    • #34033
      Wright Arms
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      There is no ‘popcorn eating’ emoji, so this will have to do.

      😉

    • #34034
      WCM
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      I had a point of impact shift this week while shooting my MS .257 Roberts.
      I have a Leupold 2.5X8 scope on it.
      I noticed I had used about all my windage getting it zeroed.

      Talked with Leupold and they told me when a scope is on the other edge of adjustment that the groups will move and it won’t hold zero.
      The rifle has a old side mount with no adjustment available.

      I switched scopes to a VX3 1.5X5 because it has twice the internal adjustment.

      I have not taken the rifle back out yet but Hodgdon Superformance powder looks like it may be a winner in this rifle.

    • #34036
      skeettx
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      Barometric pressure causing a different dwell time in the barrel
      Mike

    • #34039
      Sgt. Mike
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      I was told the same thing by Leupold years ago.
      Superformance in the .257? Interesting to know, not wanting to drift the thread just a comment.

    • #34040
      uber7mm
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      I’d eliminate the possibility of a bad scope. Try a different scope of a known pedigree and see if you get the same symptoms.

    • #34041
      GhostHawk
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      Humidity change would be my guess, but it is just that, a wild guess.

      The good news is that a humidity change can be tested. Just need a slightly warm dry box. Put the rifle in for a day, shoot a group. Take out out for a day, shoot another, look for changes.

    • #34045
      Harter
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      Everything I would have suggested has been touched on .

      Reaching out into a realm of physics and bizarre experiences in the far West . Is your bench grounded ? Have you considered a bonding strap from the bag platform to a ground rod and to the rifle ?
      i know this is a huge reach but the potential of the dissimilar metal creating a field charge of some sort and “leaning on” the click locked adjustment .

      Reaching I know and possibly not even plausible . The insulation value of the anodizing on the scope may be enough to set up the weirdness .
      ​​​​​

    • #34046
      lar45
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      Tim’s bench is a concrete slab with cinder block legs and another slab on top,
      It’s pretty stable 😉

    • #34047
      popper
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      Assuming nothing wrong with gun, bedding, sights or shooter I would look at bore seasoning/condition and load (bullet) stability. I see this all the time with cast, pretty much never change scope settings, just from the load.

    • #34048
      Larry Gibson
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      It is a common phenomenon caused simply by the variations in temperature, humidity, consistency of the ammunition’s fps and mostly by slight variations in the shooters position. The rifle, unless of an ungodly weight, will begin to recoil before the bullet leaves the bore. Any slight change in position shot to shot, group to group or a change of shooters will cause a slight shift in the angle of departure. It’s why you get 2 or more sighters before many HP and even small bore prone match strings. It’s why in BR you can many times shoot as many sighters as you want. It’s why bench resters mark the location of their bags, the legs of the rest and even where their feet rest. It all has to do with consistency shot after shot.

      Cone of fire has to do with the accuracy potential of the rifle, ammunition and shooter. COF has nothing to do with the precision of the rifle. However, the “greater” the precision the odds are the cone of fire will be smaller. Many things affect the cone of fire and none of them have anything to do with the precision capability of the rifle. If zero’s remained constant then we could do quite well with fixed sights

      Larry Gibson

    • #34054
      kens
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      I wonder how much lighting has to do with all this.
      What if the sun was very bright, intense, and clear blue sky day?
      sun on your left? right? behind you? straight up?
      What if it was a cloudy grey day?

      I don’t know about the rest of the members here, but some of my best shooting (and hunting) was on grey days. I think the light being constant on a grey day is the best.

    • #34058
      JPHolla
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      BPCR shooters know sun angle makes a difference with iron sights. Not so much with a scope other than the sun being an annoyance and hurting your concentration.

    • #34059
      kens
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      yaaa, any kind of annoyance can move your bullet around, especially if Tim is trying to get SUB-moa

    • #34068
      Goodsteel
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      I have talked to several people about this since starting the thread. Experienced shooters who can match me step for step which is important.

      My business is building and shooting sub MOA rifles. I don’t get paid till I put ten in less than an inch, and If I don’t get less than .75MOA, I’m not happy.

      I built my shooting range for this specific purpose. My shooting bench is the “lazyboy recliner” of shooting benches. I sit in a fully adjustable office chair to shoot. When the weather is nice, I’ll take phone calls and sit at the bench while I talk to clients, or smoke a cigar and contemplate life with my elbows propped on it in shooting position. This isn’t just a shooting bench. It’s the desk I do business on.

      I also have my very own business targets, printed for me by the local printshop. They are always the same.

      Not only do I shoot very well from this Utopian shooting rest, so does everyone else who uses it. Bjornb, CAdude, Sgt.Mike, Lars45 have all sat in my place and sent lead down range.

      Any question as to the capability of my custom rifles, just ask Bjornb, Larry Gibson, Lars45, JRR, or any of the others who have experienced MBT rifles and the precision that comes with them.

      I have over 65 calibers in my lineup of dies that I can reload on demand (of course, there’s still big holes in there that I’m working on plugging). Any question to my personal ability as a shooter and reloader, ask anyone of these fellows who’s ammunition has been taken to the next level using the tools I designed for them.

      I shoot about 5 SUB MOA groups a week from this bench, with my ammunition, using custom rifles that I built in all different calibers. It’s not something I hope to do. It’s what I actually do regularly.

      I don’t say this to brag, I’m just letting you know the facts. I HAVE to shoot well below subMOA on a regular basis with an absolute smorgasbord of different rifles, calibers, and stock styles and I have tried to take every advantage I can so that I can do it sick, tired, stressed, or anything else.

      Certain things I have discounted as possible causes are:
      Ambient temperature at the range effecting the rifle/scope alignment.
      The reason for this is that by the time I shoot 40 shots through the rifle, the barrel and front ring of the action (you know that part the front of the scope is tied to?) is hot enough to fry an egg on and the rifle is still dumping the shots into the same group. Hard to see how temperature of the rifle, or differing thermals between the scope and the action could be causing this.

      Shooters position on the rifle.
      I intentionally monkey with my hold of the rifle and determined that I would have to be doing something REALLY wrong in order to throw my shots that far out of center with the rifle in question. I mean we’re talking holding the rifle at a 15 degree angle, slapping the trigger like it was a pingpong ball, and jacking with the paralax in the scope.

      If a buddy comes over to say hi, I tell him to sit down and shoot that rifle. If his 5 shot group impacts 1″ to the left. I sit down an hour later after he leaves, and stick the other five in the same 3/4″ group he had started.
      I’ve done that twice now. This also disproves the idea that the rifle was just getting used to the ambient temperature of the range that day after being removed from the temperature controlled environment in the safe.

      humidity in the room when the cartridges were loaded
      All the ammo loaded at all different times has demonstrated the same tendency, and the groups remain the same, and yet, within ammunition loaded in a single session, there will be several of these mysterious POI shifts.

      The ideas I am willing to consider as a very real possibility:
      Scope issues.
      I can’t afford Schmidt & Bender, US Optics, or Nightforce, so I have to remain vigilant about my optics and they can fail. I called Vortex and explained this issue and asked the engineer if this sounds like a scope issue to him. He said it’s very possible, but that I may have my screw torque set too high on the rings, which could cause problems with the erector return spring inside the scope. He said to dump the ring screw torque to 15in/lb of torque, run the scope through it’s motions and re-shoot. He said if the problem persists, they would be glad to repair or replace it ASAP.
      I believe this is unlikely, but I am going to take his advice right away and see what happens.

      Environmental issues.
      I think I will buy a small weather station and install it next to the shooting bench and start keeping track of Barometric pressure etc etc etc. I doubt very seriously this is causing an issue, but it might explain why I seem to have a harder time shooting when the weather is in flux. Or it might confirm what I already believe to be true: “at 100 yards, it really takes a special level of jacked up to mess with a group. Either way, we’ll see what happens.

      Light.
      If there’s one thing I believe in, it’s that light is a movable thing and can mess with a group very easily no matter what sights you might be using. I’ll start taking note of where the light is coming from and how hard it’s coming in. etc etc etc.

    • #34069
      Goodsteel
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      I’m going to eliminate this as a possibility first.

    • #34071
      Goodsteel
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      I talked my problem over with an optics engineer. He said one way I could satisfy myself that the scope is, or is not readjusting as it sits idle on the rifle is to mount it outside on a solid steel base placed on my bench, and pointing at my target backer with four points of aim. He said adjust the scope so it is aiming at the first point and walk away. The next day, check it and see how close it is to where it was set. Note the change (if any). Readjust to the next POA. Repeat.
      If the scope never moves, then it must be either the shooter, the rifle, the environment, or all three, but the scope must be eliminated first. It’s the lens through which everything is judged.

    • #34072
      popper
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      humidity will only diffuse ( blur/dim) the target image. High humidity can act like a prism so rainbow. Heat from barrel can mirage the target. SgtMike recommended a heat shield when I asked about target picture dimming after a few shots ( good Nikon). Didn’t effect COF. I suggest non stable bullet (helix path) and/ or barrel condition. You could use your optician recommendations and also try heating the mount watch for movement. Not an optical guy but did a lot for DOD stuff. You could also blow hot air down the barrel with gauge on the end to see movement.

    • #34073
      WCM
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      The scope can readjust by itself , or with the aid of the recoil of the rifle.
      My suggestion would be what I have done.
      Change scopes, and see.

    • #34074
      Larry Gibson
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      It’s not the optics shifting otherwise you would not consistently shoot sub moa groups. They would shift because there’s something loose allowing movement and that would occur within the groups also. That’s obviously not happening.

      Whether one realizes it or not, every time you sit down at the bench or assume any other shooting position, especially if there’s activity between groups/relays you will likely have a slightly different position. Add to that a small amount of optical distortion because of humidity and mirage and the poi will shift slightly. This last Sunday we saw an excellent example. Shooting F class at 300 yards where the 10 ring is 2.76″ diameter. The top shot there (no it isn’t me) fired 5 sighters and was on so he shot a 200 with 14 Xs. We went down and put up new targets giving a 20 minute break between relays. Next relay he shot 1 sighter which was a low 10. He though he was good so he shot for record. He dropped 3 nines out the bottom because it warmed up and the mirage had moved the bullet up about 1″. In other words, the image we were seeing was 1″ higher than the actual target was. I also lost points out the bottom until I adjusted for the mirage. So did everyone else.

      Unless you adjust for those conditions (shooter position inconsistencies….yes everyone has them to some degree and the conditions of wind, temperature change and mirage) you will have poi shifts even with rifles of the greatest precision. Again, It’s why most matches allow sighter before and sometimes during strings of fire for score of group. That be the phenomenon…….:(

      Larry Gibson

    • #34075
      Rattlesnake Charlie
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      Just listen to Larry Gibson.

    • #34076
      popper
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      125F front scope mount and 70F rear for 1/2″ steel ring base and 3″ between gives ~1/2″ error @ 100 yds. Don’t know what the 0.0004″ expansion does to the scope. Anyway, one possible explanation. Shouldn’t try to do this math in my head late at nite while watching TV.

    • #34107
      Goodsteel
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      Larry Gibson;n14931 wrote: It’s not the optics shifting otherwise you would not consistently shoot sub moa groups. They would shift because there’s something loose allowing movement and that would occur within the groups also. That’s obviously not happening.

      Whether one realizes it or not, every time you sit down at the bench or assume any other shooting position, especially if there’s activity between groups/relays you will likely have a slightly different position. Add to that a small amount of optical distortion because of humidity and mirage and the poi will shift slightly. This last Sunday we saw an excellent example. Shooting F class at 300 yards where the 10 ring is 2.76″ diameter. The top shot there (no it isn’t me) fired 5 sighters and was on so he shot a 200 with 14 Xs. We went down and put up new targets giving a 20 minute break between relays. Next relay he shot 1 sighter which was a low 10. He though he was good so he shot for record. He dropped 3 nines out the bottom because it warmed up and the mirage had moved the bullet up about 1″. In other words, the image we were seeing was 1″ higher than the actual target was. I also lost points out the bottom until I adjusted for the mirage. So did everyone else.

      Unless you adjust for those conditions (shooter position inconsistencies….yes everyone has them to some degree and the conditions of wind, temperature change and mirage) you will have poi shifts even with rifles of the greatest precision. Again, It’s why most matches allow sighter before and sometimes during strings of fire for score of group. That be the phenomenon…….:(

      Larry Gibson

      Thanks, and absolutely no argument Larry. I’ve seen this myself, and I expect it at extended ranges.
      If at 300 yards, the mirage changed the POI by 1″, that would be a corresponding .33 inches at 100 yards, which I would not worry about.
      I just think that 100 yards is a little close to be blaming the weather. I’d willingly blame a 1/2″ shift on humidity, mirage, barometer etc etc etc, but more than that, and I smell a rat.

      I could be wrong, and I’ll admit it if I am. I have to find out though.

      I’ve ordered a one piece rail and rings for the rifle in both 30mm and 1″.
      I’ll try several scopes and see what gives, and report back. If things do not improve, I’ll slap the mat.

    • #34120
      Anonymous
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      I just found this and printed it off for my range bag –have to try it next range trip— TORTURE TESTING YOUR SCOPE

      http://www.longrangehunting.com/articles/setting-up-scope.php

    • #34121
      Goodsteel
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      This scope is one that I use for proofing new builds, and I have performed the first, non rifle specific part of that “torture test”. I really don’t see it as much of a torture test. That’s just what you have to do to make sure you have reliable optics in the first place. That does NOT mean that they will continue to perform. I’ve seen every sub $1000 scope brand fail miserably at one point or another. It’s not a matter of “If” but “When”. That’s why warranty is so important to me along with having several proven scopes to co-witness the results with.

    • #34123
      GhostHawk
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      You want to learn about shooter inconsistancys, buy a 150$ spring powered break barrel air rifle.

      Changing a finger position a quarter of an inch can move center of group an inch.

      And because of the nature of the beast, you have to crank that barrel down, compressing the spring for every shot. There is not perfect 5 shot or 10 shot group without learning to be consistent. Me I cheat a lot, I shoot indoors, at close ranges, longest I can, but 20 feet is not far.

      Even so a slight movement of the cheek on the cheekpiece means a slight change of the eye position, and that #4 shot of what is shaping up to be a perfect 5 shot ragged hole is suddenly out of the group. Only a quarter of an inch at close ranges, but enough to show that I screwed up.

      And that is with the gun resting on a towel on the back of an office chair right in front of the trigger guard. About as ideal for springers as it gets.

      Gun is still shooting tight groups, but a change in eye position can move the group.

      But test it for yourself. Be sure.

      IMO your problem tells me that you have gotten so good at building rifles that the only remaining problems lie with the shooter.
      And the shooter ain’t bad either, or it would happen more, and more widely varying.

      “He whom the God’s would destroy, they first make mad”

      Go offer up something to the shooting gods Tim. Make it worth their while.

    • #34131
      Goodsteel
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      GhostHawk;n14992 wrote: You want to learn about shooter inconsistancys, buy a 150$ spring powered break barrel air rifle.

      Changing a finger position a quarter of an inch can move center of group an inch.

      And because of the nature of the beast, you have to crank that barrel down, compressing the spring for every shot. There is not perfect 5 shot or 10 shot group without learning to be consistent. Me I cheat a lot, I shoot indoors, at close ranges, longest I can, but 20 feet is not far.

      Even so a slight movement of the cheek on the cheekpiece means a slight change of the eye position, and that #4 shot of what is shaping up to be a perfect 5 shot ragged hole is suddenly out of the group. Only a quarter of an inch at close ranges, but enough to show that I screwed up.

      And that is with the gun resting on a towel on the back of an office chair right in front of the trigger guard. About as ideal for springers as it gets.

      Gun is still shooting tight groups, but a change in eye position can move the group.

      But test it for yourself. Be sure.

      IMO your problem tells me that you have gotten so good at building rifles that the only remaining problems lie with the shooter.
      And the shooter ain’t bad either, or it would happen more, and more widely varying.

      “He whom the God’s would destroy, they first make mad”

      Go offer up something to the shooting gods Tim. Make it worth their while.

      As it happens, I have experiance with precision air rifles. My favorite rifle is a Daisy Avanti with aperture sights. Its very light, and has a long smooth trigger pull. When I was living in town, I would practice with it for the very reasons you site. Its a very strict schoolmaster.
      Now that I’m out in the country, and shooting regularly, I lent that rifle to Bjornb when he visited recently because he’s in the same situation I was.
      Cool story about that rifle.
      I was at a men’s retreat with the fellows from church about five years ago. One of the leaders had brought two of these rifles by the shop to be sighted in a week previous and informed me that we were to have a shooting match with these rifles as part of a “team challenge”. I sighted the rifles in, and found that at the stated distance, they were capable of putting five BBS through a ragged hole. But only if the shooters form was perfect.

      Once we had all arrived at Shepherd of the Ozarks, we studied scripture and heard inspiring messages from several speakers and played board games till far into the night. The key message of the event was something to the effect of ” hitting your mark” and the airgun match was the big event.
      All the men were divided into teams of 7 fellows. My team was rather shy on marksmanship as two of my teammates had never pulled a trigger in their lives. We had only moments to discuss the principles of shooting, and I did my best to educate them on the fundamentals, crash course style. I told them to take a prone position no matter what. One teammate was to hold my hat to shade the rear sight for the shooter, and another was to load for him so he didn’t change position. I smoked the sights with a lighter, and then it was our turn to shoot. I was missing a teammate, so I had to shoot twice. The mark was Birchwood Casey 2″ target spots at 5 meters. The stickers were placed seven in a row on card paper with each shooters name written in marker above his target. As a joke, they had placed a 1″ dot under my name. I was thinking they just screwed up, because the 1″ dit fit the apertures better, but they all laughed and replaced it with the 2″ dot. Oh well!
      each of my shooters took their turn, and I went last. I shot the black out of the center of both dots. Five shots each, only one bb landed outside the black diamond. Unfortunately, the other teams were more ballanced in their marksmen, and my team took second place.
      Later the fellow that had supplied the rifles asked me about rebluing an engraved Sweet Sixteen of his that had no finish left and some rust. I told him I’d do it in trade for the rifle I used earlier and he agreed.
      I spent a lot of time with that rifle ever since.

    • #34133
      Goodsteel
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      Concerning the rifle in the OP, I’ve taken a fresh look at it and decided to make several changes (I know this violates the scientific method, but I have reason to). I decided to install a one piece rail, and change scopes.
      The way I see it, I just want to know if the scope is at fault, or if the problem is either shooter or weather related. I’m eliminating the scope first (I hope) then, I will work on the other factors.

      I suppose I just need to buy a warehouse to shoot in. LOL!

    • #34152
      WCM
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      I think you are on the right track.
      I often wonder how many times over the years I have blamed a rifle or load when it was the scope or mounts.

      I took my Leupold 2.5X8 off of my .257 Roberts and put it on my .444 Marlin.
      Soon I will know if the scope has a problem.

    • #34257
      WCM
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      My 444 made the point of impact dance all over the target.
      Today the Leupold 2.5X8 goes back for service.
      It is a thirty year old scope.

    • #34259
      Goodsteel
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      I have discovered the problem. I hesitated to post till now as I have been testing to make sure.
      The one piece scope rail and Warne rings was the cure.
      In the OP, i described a wandering POI where my groups would shift haphazardly from session to session, and wander as much as an inch off POA, but remain consistent within that shooting session.
      The possible causes were guessed as being scope failure, environmental conditions, ammunition, or shooter error. None of this was correct.

      In the past couple weeks, I have observed no change in POI except that which you might expect from heavy wind (my group was moved .6″ to the left by a 10MPH wind from the 4:00-5.00).

      I proved this twice and adjusted my POI to POA. The next three groups were started by clients that were intrigued by the rifle and wanted to shoot it (I did not tell them about this background test until after they had shot). I simply gave them quick pointers on how to work the bags, and how the rifle likes to be held, and their shots went exactly to POA. After they left, I would finish the 10 shot group, then shot a second one, both of which measured identically, including the client’s first shot and my own (which demonstrates the repeatability of my shooting bench setup).

      One of these clients brought his own 6X45 rifle that I built him back in 2015. Not only did we both cover each others POI with the respective rifles, but we swapped ammunition and the results were the same. Both rifles preferred each others loads as much as their own (which proves the repeatability of Krieger barrels with MBT rifles built around them).

      Last night, was the final test as the weather has changed again, a different batch of ammo was loaded, and the rifle has set in the safe for a few days. A client was here, and I asked if he would like to shoot the 6X45. He jumped at the chance.
      I told him to just dry fire the rifle a few times to get married to the trigger, and to keep a bit of thumb pressure on the stock behind that cocking piece to tame that last little bit of cross hair jump. He did so and agreed he was ready, so he dropped the first shot on the follower and bolted it home.
      I told him to take a fine bead on the 6:00 point of the 4″ diamond and squuuuuuueeeeezzzzzeeee.
      The rifle barked and the tip of the point disappeared. He looked over at me and said “Holy crap”. I told him to throw in another one down there. He repeated the performance, but I saw the grass lay over a little from a sudden breeze. Mentally, I called the shot 1/4″ to the left, but it didn’t move that much and turned his first shot into a sidways figure 8. He said “Sorry I guess I pulled that one”. I told him no, he did perfectly but the wind got him.
      The next shot split the difference between the two, and at that point he quit and got up from behind the rifle. He said “that’s one crazy accurate rifle!”. I agreed, happy to agree with him mentally because now the rifle is both precise and accurate. (This proves the repeatability of the scope and ammo).

      When my 300WinMag was on it’s previous barrel, I had Leopold two piece bases on it as well when I observed this POI shift.

    • #34270
      Wright Arms
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      Goodsteel;n15170 wrote: I have discovered the problem. I hesitated to post till now as I have been testing to make sure.
      The one piece scope rail and Warne rings was the cure.
      In the OP, i described a wandering POI where my groups would shift haphazardly from session to session, and wander as much as an inch off POA, but remain consistent within that shooting session.
      The possible causes were guessed as being scope failure, environmental conditions, ammunition, or shooter error. None of this was correct.

      In the past couple weeks, I have observed no change in POI except that which you might expect from heavy wind (my group was moved .6″ to the left by a 10MPH wind from the 4:00-5.00).

      I proved this twice and adjusted my POI to POA. The next three groups were started by clients that were intrigued by the rifle and wanted to shoot it (I did not tell them about this background test until after they had shot). I simply gave them quick pointers on how to work the bags, and how the rifle likes to be held, and their shots went exactly to POA. After they left, I would finish the 10 shot group, then shot a second one, both of which measured identically, including the client’s first shot and my own (which demonstrates the repeatability of my shooting bench setup).

      One of these clients brought his own 6X45 rifle that I built him back in 2015. Not only did we both cover each others POI with the respective rifles, but we swapped ammunition and the results were the same. Both rifles preferred each others loads as much as their own (which proves the repeatability of Krieger barrels with MBT rifles built around them).

      Last night, was the final test as the weather has changed again, a different batch of ammo was loaded, and the rifle has set in the safe for a few days. A client was here, and I asked if he would like to shoot the 6X45. He jumped at the chance.
      I told him to just dry fire the rifle a few times to get married to the trigger, and to keep a bit of thumb pressure on the stock behind that cocking piece to tame that last little bit of cross hair jump. He did so and agreed he was ready, so he dropped the first shot on the follower and bolted it home.
      I told him to take a fine bead on the 6:00 point of the 4″ diamond and squuuuuuueeeeezzzzzeeee.
      The rifle barked and the tip of the point disappeared. He looked over at me and said “Holy crap”. I told him to throw in another one down there. He repeated the performance, but I saw the grass lay over a little from a sudden breeze. Mentally, I called the shot 1/4″ to the left, but it didn’t move that much and turned his first shot into a sidways figure 8. He said “Sorry I guess I pulled that one”. I told him no, he did perfectly but the wind got him.
      The next shot split the difference between the two, and at that point he quit and got up from behind the rifle. He said “that’s one crazy accurate rifle!”. I agreed, happy to agree with him mentally because now the rifle is both precise and accurate. (This proves the repeatability of the scope and ammo).

      When my 300WinMag was on it’s previous barrel, I had Leopold two piece bases on it as well when I observed this POI shift.

    • #34272
      kens
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      So, what all did you do here?
      did you previously have a 2-piece rings mount? and you now installed a 1-piece mount?
      Are you saying there is a slight bit of flex in the receiver with the 2-piece mounts?

    • #34276
      Goodsteel
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      What I’m saying is that for some reason, the two piece base and Leupold twist front and two screw rear, allowed the scope position to migrate when at rest.
      The screw torque was set by myself at 27in/lb, and the screws were set with loctite 271. This is an irrefutable fact.
      Installing a one piece base and Warne rings, using the exact same method, cured the POI shift perfectly.
      There have been a couple times I thought the POI shifted 1/8″ or so, but I was easily able to explain the trend with weather conditions, shooting two days in a row with similar wind from 3:00 etc etc etc. What was happening before was completely unpredictable.

    • #34279
      kens
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      I saw some new mounts (new to me anyways) the other day.
      They were 1-piece mount with the bottom half of the rings were one piece with the base.
      they were aluminum, and being all 1 piece on the bottom half of the rings as well, I bet they are pretty good.

    • #34281
      Goodsteel
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      I don’t know if the problem was totally confined to the two piece bases, or if it was the twist-lock and double screw arrangement. Regardless, you’d have t ohave a pretty darn accurate rifle to even see the difference in the first place. Any rifle that is shooting more than 1.5″ for ten shots wouldn’t matter one iota.

    • #34300
      Bodean98
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      I have always been suspicious of the twist in mounts, even the one piece mount. Nothing that I have ever proven but just a suspicion. I was never able to get them lined up properly with each other without using the scope mounted in them. Short of using a 1″ pipe or steel rod (which I never seemed to have) I’m not sure how you would go about it. Wooden dowels didn’t work worth a flip. I much prefer Weaver style or Talley mounts and rings.

    • #34301
      Goodsteel
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      That’s easy. Use a lapping rod to twist them in and then loosen the screws and lap the rings. Poyfect.
      The big question is, do they stay put, or migrate slightly. I’m pickier than most, and I’m not to quick to shrug off variances (as this thread shows) so I was able to see and eliminate the problem, but I’m sure there are countless shooters who are happy to just keep adjusting POI to POA.
      I don’t know. Its just something to watch for.

    • #34572
      Goodsteel
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      I have just shot the rifle again having left it dormant in the safe since my last update. That’s two weeks, and the weather has warmed significantly and dried out a lot as well.
      The first shot from the cold barrel landed 1/4″ to the right of the POA.
      Then I started cutting sticks in half with it. One of them was about 4′ tall and had a shot up pop can on top of it. It was about .4″ in diameter. Took three hits to pop it in two and the can came swinging down.
      The rifle is back in the safe, and I am totally confident that I can remove it from the safe and blow a buzzards head off at will. Or I might shoot a coyote in the eye. It doesn’t matter. The point is, the precision in the rifle is USABLE now, and not just impressive.

    • #34576
      popper
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      I use P.E.B.R type steel mounts on the ARs, Pull them off, change rifles, etc. no noticeable change in POI. Scopes are Niko 6×24.

    • #34630
      DallenK
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      Very happy to hear you have figured this out. I may change mine to a one piece base as well. From time to time my poi will change 1/2 moa. And this may be my issue as well.

    • #34632
      lar45
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      Goodsteel;n15170 wrote: I have discovered the problem. I hesitated to post till now as I have been testing to make sure.
      The one piece scope rail and Warne rings was the cure.

      When my 300WinMag was on it’s previous barrel, I had Leopold two piece bases on it as well when I observed this POI shift.

      Makes me wonder if the 2 piece base was the problem, or the Leopold twist in style base that was the problem??

    • #34634
      Waksupi
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      Most factory rifles are not blueprinted. If the bridge and ring are not even and leveled, it can cause all kinds of problems.

    • #34635
      Wright Arms
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      Could you elaborate on how to check for such a condition? Is a lapping bar all that is required, or are there even more accurate evaluation means?

    • #34639
      Goodsteel
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      This one was very straight as is. The one piece base needed no bedding at all, and the twist in rings required little in the way of lapping.

    • #34640
      Goodsteel
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      Wright Arms;n15721 wrote: Could you elaborate on how to check for such a condition? Is a lapping bar all that is required, or are there even more accurate evaluation means?

      The truth is, I do not know what to be checking for. I do not know why the POI shifted, nor why it took a week for it to happen each time.
      The bases were secured to a straight receiver and were set with LocTite 271 red, the front ring twisted in tight, the rear opposing screws were firmly torqued, the rings were lapped together, and the ring screws were evenly torqued and set with LocTite 271. Untill a few weeks ago, I would have sworn this was as good a system as any other with the only downside being the difficulty of switching scopes (as opposed to a Weaver rail).

      The test here is irrefutable though. I accept this as something that only a truly precise rifle would be able to notice, and since precision is the name of the game, for the moment at least, this will simply have to be added to a few things that I do because the results are what they are. I am confident enough in my installation of the original rings and bases that my test here demonstrated a clear advantage to the Weaver rail over the twist lock Leupold mounting system, and I will not be using the Leupold twist lock again unless I am specifically instructed to do otherwise.

      BTW, the rifle was shot yesterday, and the POI is still within 1/4″ of POA.

    • #34651
      Waksupi
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      Wright Arms;n15721 wrote: Could you elaborate on how to check for such a condition? Is a lapping bar all that is required, or are there even more accurate evaluation means?

      You need the appropriate bases, to start with. Also some sort of marking medium to transfer contact marks. First thing to do is put a straight edge across the tops of the secured bases. If they are not perfectly level, you start in with a diamond stone, to bring down whichever is needed.

      I usually go ahead and stone the top of the receiver before starting the leveling process. Most are off considerably as new. Pretty much impossible to tell by looking at them, the only way they become obvious is when you are stoning the action.

      Even custom actions need checked, as blueprinting is all hand work. You might look at the Cast Boolits Gunsmithing sticky, Joni Lynn’s Mauser, for some pictures of the process.I didn’t go into a full description of what I was doing there, but it gives you an idea.

      Then you need a small machinist level. Have the action secured in a vise, and leveled from the bottom. Then put the level across the bases, to see if they match, and don’t tilt left or right. If not, back to the diamond stone. That’s what the transfer marker is for. Once you have this accomplished check to make sure the bases are contacting the receiver evenly. Then go back and check your other critical things.
      This process can take anywhere from a couple hours, to a full day.

      A lapping bar does not cure the problem, only hides it. And not very well.

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