April 3, 2018 at 10:10 am #49941
I tried to post a rather well thought out test once before but the forum wouldn’t accept it …… I blame my isp routing through Cali ……..
We’ve all done load development to match a particular combination of parts . I’ve read enough and had some experiences to reenforce a muzzle of 3+ groove dia and the slowest twist for 100% stabilization of appropriate bullet lengths . Speed kills except when it doesn’t and if you burn enough powder to make a great Cal wonder cartridge the throat doesn’t last very long .
There have been 100 documented tests about barrel length and velocities and 7 for 10 if you shorten it shoots better per load .
My inquiry is if we have a full bull barrel , for example a heavy blank and we thread to a known action and polish the black of just enough to get it centered .
Work up a load in a spirited cartridge that is known to be long lived . 7×57 , 06′ , 338 FC for example . Shoot a 100 rounds @ 3-6 a day .
Then turn the barrel for a standard taper action dia 3″ out to a .960 muzzle . 10-20 rounds to adjust the load POI etc then 100 rounds 3-6 a day .
Turn it down again straight taper from 3″ out to a .750 muzzle
Repeat the test .
Turn it to a .960 step from 3-3.5″ out and taper to .750 .
Shoot the test .
Turn the barrel to a heavy Mauser step say .960 for 3″ the a .2 step to .855 for 8-10″ and a .2 long step to .760 .
Shoot the test .
Turn it to a lightweight conture with a .680 muzzle.
Probably a test like this would be best served by a single load for a light barrel at the highest practical level being fired in all 5 profiles , unfortunately we can’t add it back after we take it off .
Of course this kind of a test is useless to match or long range shooter but would provide valuable information for a hunter/varminter “population control specialist” . It would allow a limited test of profile effect on net barrel accuracy by shooting multiple profiles on a single action , head space , barrel , chamber and crown . Removing about 800 variables from 5 “identical” rifles .
Induced stress from the machine work …… I got nothing here unless there is an in someplace where the barrel could be liquid nitrogen dipped between steps . I don’t see where there would be a significant amount of stress induced over a normal cut to profile because it’s being done in increments it might be less stressed than a barrel straight cut to a particular profile in one cut .
So that’s my preponderance of late .
April 3, 2018 at 1:30 pm #49944ArtfulParticipant
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Have you looked at these links?
What Contour (Diameter) Should I Use?
For a gun to use for both short-range and 600-yard Benchrest competition we would use a Max Heavy Varmint taper or something very similar. This will be 1.250″ at the receiver running straight for 5″ (measured from bolt face), then tapering in a straight line to about .92″ at the muzzle, finished at 27″-28″. For 1000-yard competition, you can run a heavier taper such as the MTU, as long as the receiver or a barrel-block provides sufficient support. For point-blank shooting, if you are not planning to compete in NBRSA or IBS registered matches, we would consider a near-full contour, running 21″ to 23″.
My experience is that you can certainly have an accurate light weight barrel but the more shots thru it the more it loses it accuracy over the short period of time compared to the heavier barrel. The more rigid barrel due to larger diameter will remain accurate as you heat it up compared to a sporter barrel.
April 3, 2018 at 6:09 pm #49953
I got the part about removing metal and barrel flexation/deflection . My curiosity is if we have a premium barrel of optimal internal dimensions and finish what is the exact cost of changing it’s profile .
Let’s take this to a seen but just silly extreme for barrel rigidity . I’ve seen a 1″+ 22 LR barrel 1-9″ twist , I mean really we’re dealing with a 1200 fps 35-40 gr bullet working with like 16kpsi if you broad sided it at mm’s the barrel isn’t going to flex .
If we flip the cartridge to say a 22/06′ give it a 1-9″ load it up with a monolithic brass bullet jacked up to 65 kpsi , it’s going to move a bit . But the bullets are will hit higher and maybe double the 100 yard and in 500 rounds you’ll be looking at a 6mm throat .
The same is going to be true if we apply this to a barrel cut down to a feather weight barrel for the 22 LR but that 22/06′ is going to look like a runaway fire hose .
To a lesser degree the larger the cal gets the more strength loss we will see as the video notes . I’m not sure I agree 100% on the fluting . Because to a point as you add surface area and perpendicular lines you will gain strength and rigidity at least in crush but cooling grooves aren’t on this plate .
April 3, 2018 at 6:27 pm #49955Rattlesnake CharlieParticipant
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Barrel harmonics are a science/magic unto themselves. We vary velocity with different loads to find where that barrel is happy. Wasn’t it Browning that had that adjustable nut at the muzzle to tune most any load to increase accuracy? Physics show that short and fat vibrates less, and long and skinny more. Like most everything else in life, it comes down to cyanide or arsenic. And, patience. Lots of it. Don’t forget to know when to give up on a dead horse.
April 3, 2018 at 7:29 pm #49956kensParticipant
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When do you give up on a dead horse?
1 MOA? 1/2 MOA? 1/4 MOA?
Define dead horse in a project like this?
April 4, 2018 at 10:22 am #49962
The BOSS system . Ballistic Optimising something .
The real question would be to find out if a barrel was consistent more because of of its core or case , in a manor of speaking .
Perhaps something like this could provide insight to what makes those Mauser GI barrels shoot beyond their weight .
Beyond aesthetics wouldn’t it be a ticket for a pack rifle to be able to still be a 300 yd rifle at the gain of 2oz and keep a top step load ?
I’ve many times been tempted to buy an M70 or 700 1.25″ bull take off barrel , lots of them are 26″ and chambered for someones pet BR cartridge ….. So cut to 22″ all trace of any chamber is gone and it might make a good bed . Alas I lack the tools skills and as of now and at least the next yr time to do such a test .
I’ll get to go to one more show before I pack up the faux Christmas , that’s what we call it when you open a box in 2 yrs and wonder why you packed that particular thing or find the one you were sure was gone for good .
April 4, 2018 at 2:00 pm #49963GoodsteelKeymaster
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The thing you have to consider in this is that a rifle does not shoot to a certain MOA all it’s life. Precision ebbs and flows slightly as the round count progresses. Things are always changing as a matter of course. Add to that a profile change and you’d have to have a second barrel that you leave alone at full truck axle configuration and shoot side by side throughout the tests.
It costs about $200 to change profile. So there’s that to consider.
There is a metric ton of misinformation about barrel harmonics out there, mostly posted by folks who shoot three shots and write a book about it.
What I have seen is a 25-06 I built here at MBT (one example. I have many to fall back on) which was bedded stem to stern with an extremely long forend (26″ sporter barrel protruded the end of the stock by about 3″). This rifle was test fired rapidly and slow with ten shot groups. The slow group was nice and round at about 3/4″. The fast group walked as the barrel heated, producing a group that was 3/4″ tall and 1.25 long. That was 12 shots banged out fast and hard after the initial warmup shots then the first ten shot group, two after a scope change then ten more fired fast.
The point is, much of the talk people put out there about barrels heating and walking is merely another way for them to explain away the shoddy precision their rifle is exhibiting. I think if they were to start shooting ten shot groups, and let it be what it is without the narrative, things would become much clearer.
The internet is awash in information put out there by folks trying to convince themselves and everybody else that a cheap factory rifle barrel is just as effective as a Krieger, and it just doesn’t wash. Fact is, it’s a lot easier to type than it is to rebarrel, so don’t be fooled.
I’ve got a Winchester Model 70 here I inherited from my uncle when he passed. It shoots nice, round, 2.5″ groups with known loads. A fellow was in the shop and saw that rifle and was impressed. He explained that he used to have one just like it, and he could shoot dime sized groups at 200 yards with Remington Cor-Loct ammo……… I just smiled and said “that’s real good shooting. This one shoots like garbage. LOL!”. Of course, then he proceeded to tell me I just have to find “the load” etc etc etc. Fact is, I already found “the load” it’s a good load across the board with good rifles, and the fact that my rifle will not shoot that load anywhere near 1MOA means my barrel is garbage. I’m fine with that. One day, I’ll screw in a Krieger. Any Krieger. Any profile. Any length. And when I do, it’s going to shoot 5/8″ groups and when I find “the load” it will shoot 1/2 MOA. Sometimes it will shoot 1/4MOA, and sometimes 5/8, but the average will be 1/2. That’s without changing ANYTHING. It ebbs and flows and I’m fine with that.
There’s no need to overthink this. Good barrels shoot tight patterns, bad barrels don’t, and good barrels don’t happen on accident.
With that knowledge firmly in hand, I would worry about a test like this being inconclusive. At the best, it might reinforce something I already knew, and at the worst, it might lead me to a conclusion based on insufficient data. In order for it to be conclusive, several barrel pairs from several manufacturers would need to be tested in tandem with multiple loads and all the data carefully recorded. Scientific method would have to be adhered to like glue, and the test would have to be conducted by someone who was willing to start over from scratch if need be, and if the test proved nothing after being conducted, this man would have to have the spiritual cajones to tell the truth about that and not lean on theories about what he thought he saw/proved.
I could almost get excited enough to make that happen, but that last part would be a pill too tough to swallow for me personally. I would HAVE to have something to show for all that work, and if there was nothing, I think I’d have to have a stiff drink.
Just some things to think about.
April 4, 2018 at 6:20 pm #49969
I’ll just have to find a sponsor and another bottle of Boolet Rye . 🙂
The world may never know .
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