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    • #22438
      Goodsteel
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      I am working on a bullet catcher right now. I have all the pieces lined up and I’m gathering them up.
      I started a few days ago by calling the local paper company. Took a few phone calls, but eventually, I was talking to the main man himself. I greeted him like a friend asking for a favor, and told him I was looking to get my pickup truck filled up with fine sawdust. He asked me what in the world I needed that for, and I explained that I am a gunsmith and I have learned how to shoot cast bullets at nearly 3000FPS, but with each twist rate, there’s a very specific point past which accuracy is lost completely, and I want to catch the bullets and see if I can figure out what is going on. He said it was such a coincidence that I called him because he was looking for a gunsmith to remove a choke from his shotgun. I told him I can make that happen.
      So, yesterday, I called on Lowes Home improvement warehouse and picked up supplies for the bullet catching box. I’ll let the pictures do the talking:

    • #22439
      Goodsteel
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      So, now I had a box for to shoot my HV bullets into. Here’s a few pictures of what happened the next day:


      Dont read too much into the groups. The object here was to shoot as BIG a group as possible to avoid strikes within the box.

    • #22440
      Goodsteel
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      These bullets were cast of Lyman #2 and fired at 2900FPS give or take 50 FPS

    • #22442
      Artful
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      I’m surprised the sawdust did so well at catching them without causing more upset. Just make sure to cover it from rain – that changes the way it behaves quite a bit once it gets wet from my old memory of shooting into a pile of it.

    • #22444
      Goodsteel
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      Continued….

    • #22445
      Goodsteel
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      Here’s the recovered HV bullets:

    • #22447
      Goodsteel
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      OK, so you might say “Cool, ya caught some bullets. Good for you.”

      Well friends, let me bring the rest of the story to you.

      This band measures .308 as you would expect:

      This band measures .306

      This band measures .304

      And the shank area under the GC, was sized down a whopping .008

    • #22448
      Goodsteel
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      I believe that lube itself is sizing the bullet down hydraulically.

    • #22486
      az-jim
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      Goodsteel;n206 wrote: I believe that lube itself is sizing the bullet down hydraulically.

      I’m definitely curious.
      How would the lube size the bullet hydraulicly with centifigal force? Is this based on an equal and opposite reaction theory ?
      Looking at the pics, my first thought was the rear of the bullet being shoved forward as the front slows down and material being displaced, sort of like when a casting cools it pulls material from the sprue.

    • #22506
      Goodsteel
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      I’m willing to entertain any theory, but I don’t see how centrifugal force could have any effect on this at all. Especially inside the barrel. Everything we know and are taught about cast bullets says that anything done to them makes them get bigger, not smaller.
      In fact, the only thing that can make a cast bullet smaller is being sized down by the a bullet sizer or the case neck.
      These bullets were cast of Lyman #2 and sized to .310. They were seated in a case neck with only .002 constriction, which was not enough to size the bullet at all.
      From that point, we know that if all things are normal, the powder kicks the bullet in the pants, and it is either strong enough to stay the same size, or it is bumped up by the laws of inertia.
      Then it travels down the barrel riding on a film of lube. (I would humbly ask, how that is possible if the bullet is the same size as the barrel? How is there a film of lube left in the barrel if all the lube is ahead of the GC? Obviously, there must be some slight sizing of the bullet to make room for the lube film otherwise there would be no such thing as “seasoning” your barrel with lube.)
      Then the bullet emerges from the barrel spinning 140,000ish RPM.
      The centrifugal force, as well as the sudden release to the atmosphere, causes the lube to evacuate the grooves (more or less) and if there is any effect on the alloy of the bullet, it would obviously be to make the bullet get bigger. Not smaller.
      These forces slowly relax as the bullet flies towards the target
      Finally, we have impact with the target, which we know does anything but make the bullet smaller.

      The only logical conclusion I have is that the lube itself sizes the bullet down. I think that at the speeds I am shooting (well in excess of 2400FPS) the lube does more sizing that usual. I figure there is a high pressure area, a bulwark if you will, at the base of the bullet because that’s where all the pressure is coming from, and that is exactly where the worst of the sizing happened. Almost like an acetylene torch, the closer you get to the power, the more effect it has on things even in a constricted area.

      I believe this is what has prevented us from getting past 3000 FPS with consistent accuracy. The big question is, how do we work around this?

      What do you think? Am I missing something obvious?

    • #22509
      az-jim
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      I too am willing to entertain any theory. I am certainly no expert with what makes cast bullets tick. So… if the theory is the lube, then to prove it you would need to eliminate the lube and run the same test. To my knowledge powder coat will be the next best and possibly superior choice. Again not an expert.
      This is all based on a specifically chosen alloy correct? If a harder alloy is not an option then the above would be my next step.
      Also, the theory is that bullet deformation is occurring prior to target impact and is hindering high speed accuracy, correct? Just trying to make sure I understand what you are trying to solve.

    • #22522
      Daniel
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      I am inclined to think that the bullet base is shrinking as part of the bullet point expanding. You could add a plywood or similar baffle to the sawdust box to cause the bullet to expand just a little more and see if the base has decreased diameter to a greater degree. F.W. Mann demonstrated that bullets behave like a plug of putty and that the bullet base begins moving before the nose. The inverse of that is true, on impact, the nose is stopping while the base is still advancing. Perhaps that flow of metal is what accounts for the dimentional change.

    • #22532
      skeettx
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      Great project, wonderful pictures, what do the neighbors say?

    • #22555
      lar45
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      I would like to try shooting some without any lube at all and see what happens. We may have to spend some time scrubbing the barrel out afterwards, but I think that it would provide a baseline to start from.
      I think that slowing it down faster with a layer of plywood is a great idea to see if the base shrinks more.
      I would think that we could try filling only one lube groove and see what difference that makes.

    • #22561
      Goodsteel
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      Good to see you Glenn. Thanks for lending your property, equipment and rifle to the conducting of this experiment!

      One other thing we can try is your 45-45-10 lube.
      I was thinking, one way we can lube just the front grooves would be to dip lube nose down eh?

    • #22660
      lar45
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      Yes, I am down for what ever and when ever. We could spend an entire day on just lubing different lube grooves, but from the top down sounds very interesting. It’s your project, just let me know how I can help.

    • #22664
      Goodsteel
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      You know, ordinarily, I would think that you were being sarcastic or something, but after we ran the test in the OP and it took all day to recover 25 bullets I know better! 😮

    • #22688
      rockrat
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      Hmm, I wonder if the boolit is compressing a bit, more towards the base of the boolit. The boolit enters the barrel and is swaged down to groove size, then upon exit of the barrel, the compressive stresses are greatly lessened. As the rearward bands had more stresses due it the mass of the boolit in front of the rearward bands, once the compressive stresses are lessened, the boolit elongates a bit and the rearward bands change dimensions more than the forward portion of the boolit.
      Just a thought

    • #22749
      Anonymous
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      Very nice test box!

      Just wondering if the end of the barrel/crown has the “Lube star”?

      Also, any lead there or on the rifling?

    • #22751
      BK7saum
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      Goodsteel, good to see you are up to some good. This is a very interesting project. I would also be interested in whether an unlubed bullet or one that is lubed with 45-45-10 would have nominal .308 diameter bands. If the filled lube grooves are the problem, lets see what one looks like with unfilled grooves.

      Brad

    • #22755
      VANN
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      Looks like you could try some pc coated bullets, that should prove or rule out the hydraulic force theory.

      I do wonder if the lube could have caused the base to shrink like that, it sounds possible.

    • #22771
      Pasturedrag
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      How do PC’d boolits stand up to velocity this high ?

    • #22774
      Goodsteel
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      I’m going to be honest, I could use some help on this project gents. I have the same questions you do, but the way I see it, a series of tests done in the correct order would answer all of these questions. This is what I believe needs to be done:
      1. Shoot unlubed bullets (yeah, leading will have to be scrubbed out. No step for a stepper) and observe if this reduction in size is still present. This will answer Rockrat,s theory that it’s purely dinamic in nature. If the bullets are still sized down, then we know lube is not the cause, and there is no need to try anything different as far as that goes. A different test will have to be contructed in order to chase the questions the results of this test yield.
      2. If the bullets are not sized down, then we must conclude that lube is the culprit, so bullets with only the forward most lube groove must be shot, and recovered.
      3. In addition to test #2, PC bullets should be tested and observed.
      4. In addition to test #3 and #2, I would like to try bullets tumbled in standard jacketed moly lube.

      These 4 tests would give a much sharper understanding of what’s going on.

      Look at the receipt I posted. There are some poplar boards on there I bought to build a picture frame out of. The cost of building the box was less than $30. Can anybody lend a hand?

    • #22789
      nagantguy
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      Please keep us posted, this is fascinating and is at the pinnacle of cast boolit technology. I would also be interested to see how pc or total lack of lube would effect this experiment.

    • #22808
      Reg
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      Interesting -interesting, I have seen this somewhere before and be darned if I can remember when. Need to think on this one.

    • #22877
      Bullwolf
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      Most interesting results! You seem to have created real a nifty bullet catcher there Goodsteel.

      I’ve always found recovered bullets fascinating, though mine were rarely ever found in as nice a shape as yours.

      I made my own bullet backstop for my barn, out of multiple layers of cut laminated conveyor belt and hay. I used a large angled steel plate to catch the rest for additional insurance. Sometimes I would find undamaged bullets inside the core that I mounted the cut conveyor belt sheets on. More often than not bullets had impacted other projectiles also stuck in the bullet trap’s core, causing additional deformation. A few bullets would be found practically untouched, and looked like they could easily be loaded and fired again, minus the rifling marks of course.

      Looking at the recovered fired bullets was always educational, and sometimes even informative. I think this was the first time that I really noticed that hard commercial lubes did not entirely come off of fired cast lead bullets.

      You have taken the whole cast bullet recovery thing quite a bit farther still, and it tells a most interesting story. Very impressive, I’ll enjoy following your further experiments.

      – Bullwolf

    • #22882
      JPHolla
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      We have to break the paradigm of thinking of bullets, lube, powder, barrels, etc., in static terms, but that’s difficult because we can’t touch or see something moving so fast. I think this idea about the lube swaging down the bullet is a good one. We think of lube as relatively soft because we can smear it with our fingers, but how hard is it when bumped to 3000fps? Water is much thinner than bullet lube, but it’s like concrete if you jump off a bridge, and you would be going no where near 3000fps when you hit. Another theory I’ve considered (that I’ve never really seen others explore on the “other site”) is the fact that the propellant gases could also have a part is sizing down part of the bullet. It would be obviously possible if the base of the bullet protruded below the neck, because the force is exerted from all sides, not just the rear. But if we consider the fact that the steel barrel expands under the immense pressure of firing, and the fact that in standard chambers the neck is given room to expand to release the bullet, these gases can still reach the sides of the bullet to exert force inwards. Also, these gases at the chamber pressure involved in these full-powered loads are about the consistency of molasses as I hear tell, and with some powders I think it may even blow chunks of yet-unburned powder along the shank of the bullet. This could also account for some swaging being done as the bullet went through the throat.

      I also recall an article I read a few years ago. It was by a police forensics guy who was recounting some of the insanely stupid/dangerous guns confiscated from criminals he had run across in his career. One of them was a .22lr revolver someone had “converted” into a snubnose with the use of a plumbers’ pipe-cutter. The muzzle was left as-is with a considerable choke to it. He fired it out of curiosity to see what it would do, and he couldn’t even get on paper. He took it with him to a seminar where he knew there would be a high-speed camera to see what was really happening. Most would think the bullet would simply be swaged down to the size of the hole, because that’s what would happen if done at speeds our eyes could see. But the picture revealed the bullet had been swaged into what looked like a demented piece of spaghetti. So, swaging at high speed swages a great deal more that swaging at low speed, due to momentum I suppose. I believe this is why bullets a little too fat perform so poorly when pushed hard but can perform satisfactorily at low velocities.

      I look forward to seeing more of this. Unfortunately, the pictures some people post (like in this thread) do not show up on my computer for some reason:(. What we really need Goodsteel to do is be the first to invent a clear barrel. Then there would be no doubt what’s going on.

    • #22883
      JPHolla
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      I just tried a different browser and saw the pics. Goodsteel: Did you oil the sawdust? Could you post a picture of an unfired bullet beside one of the better fired ones, and maybe even a chamber cast? It may help us better figure out what’s going on as your very interesting project progresses.

    • #22884
      Goodsteel
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      I have a picture of the u fired bullet next to the fired one.
      I can assure you that the chamber cast looks precisely like a loaded cartridge if you cut the nose off at the ogive.

      Now, I’ll add a few more detailes to the original post. I wasn’t sure if there would be any interest in this, so I posted details about only ONE BULLET.
      The rest of the story is that Glenn and I shot 5 tests with five bullets each.
      The first two tests were shot with H414, the third was shot with IMR3031, and the fourth and fifth were shot with Aliant 2400.
      The bullets were all cast and prepped by me.
      They were cast of Lyman #2 which I mixed in the shop from known alloys.
      The hardness was 22bhn witnessed by Glenn. (The bullets were cast the day before.)
      The first string was at 2900fps (51 grains of H414) and lubed with 2700+ and you see the results.
      The second was shot at 2600fps (47grains of H414) same lube and the bullets were a couple thousandths bigger on the bottom band.
      The third was shot at 2400fps (??grains of 3031) same lube and the bullets were sized even less.
      The fourth was shot at 2400 fps (?? grains of 2400) same lube, and the bullets were sized no more or less than expected.
      The fifth was shot at 2400 fps (?? grains of 2400 (same charge)) using the stiffest lube Glenn makes at White Label (comercial 160) and there was almost no change in size (however, we only recovered 3 of this string and they hit a lot of GCs from the previous bullets, and were hard to measure.

      String #4 was an attempt to demonstrate higher pressure than string #3 with the same velocity.
      And string #5 was an attempt to effect the sizing with a “stiffer” lube. I need to measure those bullets more carefully.

    • #22903
      Reg
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      Still scratching my head on this one but do know I have seen this before. I did notice Outpost 75 has found his way over and this might be more right down his ally. Ed ?? You there ?

    • #22910
      JPHolla
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      Reg;n798 wrote: Still scratching my head on this one but do know I have seen this before. I did notice Outpost 75 has found his way over and this might be more right down his ally. Ed ?? You there ?

      If you’re referring to the sawdust bullet trap, it was in Mann’s book The Bullet’s Flight from Powder to Target. I think it deserves reading again now that I’ve been reminded of it.

    • #22911
      Anonymous
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      Hi all, good to find you again. I think Tim may be on to somthing. I read somewhere the lube , lubes the bore but also seals the bore. This sizing of the bullet may be an effect of that hydralic seal.

    • #23173
      Sgt. Mike
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      Tim I need to drop off the 1903 for the reasons that we discussed yesterday, throw that into the test on your next shoot for this exercise.
      Might not prove what we was discussing but would be a sure indicator.

    • #23177
      dverna
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      One other thought. Shooting a bullet made from a “soft” alloy vs one made from Linotype? If the mechanism is hydraulic sizing, the softer bullet should deform more than the harder alloy.

      Don

    • #23190
      Paul G
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      Tim something else to considered about your hydraulic theory, How wide are the lube grooves before fireing and how wide are they on the recovered boolit. I have always thought that lube is pushed out of the grooves by the pressure of fireing that closes up the lube groove somewhat, Of course we know that lube in incompressable so it has to go somewhere, if the grooves are getting smaller by a measureable amount this could hellp your theory that lube is present between the bullet bands and barrel surface thus sizzing the band down some. Something to think about.

    • #23191
      dverna
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      This phenomena might explain why a harder alloy can help accuracy with higher velocity (pressures).

    • #23220
      Goodsteel
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      I agree. And why BHN testing really does seem to matter. It’s a measure of how COMPRESSIBLE the alloy is.

    • #23255
      Anonymous
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      Tim, I didn’t sleep at a Holiday Inn last night and danged sure not a metallurgist but is the alloy compressible or is it displaying a malleable quality? My mentor years ago was a metallurgist fwiw.

      I vaguely recall something about an experiment utilizing potter’s clay that demonstrated very similar behavior. A cylinder of clay impacted a larger lump of the same material and as the projectile slowed the core continued forward as the front end expanded. The core moving ahead of the surrounding mass diminished the O.D. of the back end of the cylinder.

      I had the same thought as someone else regarding powder coating. If this is an effect of the waxy lube it shouldn’t happen with powder coated projectiles. If it does happen with powder coating, it is the center of the projectile moving forward, sucking down the OD of the back end of the bullet. Does that sound valid to you? Just seat-of-the-pants guessing. . .

      David

    • #23257
      Goodsteel
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      David2011;n1206 wrote: Tim, I didn’t sleep at a Holiday Inn last night and danged sure not a metallurgist but is the alloy compressible or is it displaying a malleable quality? My mentor years ago was a metallurgist fwiw.

      I vaguely recall something about an experiment utilizing potter’s clay that demonstrated very similar behavior. A cylinder of clay impacted a larger lump of the same material and as the projectile slowed the core continued forward as the front end expanded. The core moving ahead of the surrounding mass diminished the O.D. of the back end of the cylinder.

      I had the same thought as someone else regarding powder coating. If this is an effect of the waxy lube it shouldn’t happen with powder coated projectiles. If it does happen with powder coating, it is the center of the projectile moving forward, sucking down the OD of the back end of the bullet. Does that sound valid to you? Just seat-of-the-pants guessing. . .

      David

      It doesn’t sound valid at all to me, but I am hindered by my narrow experience. The only thing that sounds valid at all to me is the lube hydraulically swaging the bullet down, but that doesn’t mean that’s what is happening. This is a mystery. A complete puzzle.
      I tell you one thing, I WISH it was something like what you mention, because if it’s the lube (as I suspect), there really isn’t jack I can do about it. It’s “checkmate” because our dearest friend has become our enemy.
      On the other hand, if it’s as you suggest, there are things I can do with the bullet shape and powder selection to work around this issue?

      Curiosity is killing me, but It’s going to have to wait for a few weeks/months before I can scratch that itch.

      Honestly, thanks to everyone who has contributed a theory as to what is causing this strange phenomenon. Gives me a lot to think about!

    • #23278
      Larry Gibson
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      I’ve a bit of experience with PC’d bullets in the .223 Rem at high velocity. To keep from fouling the barrel the bullets (not on PC’d but HT’s to a very high BHN) still had to be lubed. In essence the PC’d provided no benefit either from a potential velocity increase or improved accuracy. I’ll post the write up on that test in the PC sub-forum shortly.

      Larry Gibson

      Write up is posted.

    • #23289
      JPHolla
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      Goodsteel;n1212 wrote:

      It doesn’t sound valid at all to me, but I am hindered by my narrow experience. The only thing that sounds valid at all to me is the lube hydraulically swaging the bullet down, but that doesn’t mean that’s what is happening. This is a mystery. A complete puzzle.
      I tell you one thing, I WISH it was something like what you mention, because if it’s the lube (as I suspect), there really isn’t jack I can do about it. It’s “checkmate” because our dearest friend has become our enemy.
      On the other hand, if it’s as you suggest, there are things I can do with the bullet shape and powder selection to work around this issue?

      Curiosity is killing me, but It’s going to have to wait for a few weeks/months before I can scratch that itch.

      Honestly, thanks to everyone who has contributed a theory as to what is causing this strange phenomenon. Gives me a lot to think about!

      Maybe he can extrapolate, but I took his clay cylinder example to mean that the rear end of the bullet is shrinking after the bullet impacts the sawdust and mushrooms. I don’t know if it’s what is happening here, but it seems like a very real possibility to me. We need a medium that slows down the bullet more slowly to prevent any expansion of the nose to know for sure. If it is the case, lube may not be the culprit at all, or at least not entirely. Back to your idea about lubricating only the front groove, I think it’s a good one and simple to try. But I wonder about all the voids back there possibly causing problems if the alloy is not hard enough. I’m really starting to wonder about removing the rear lube groves right up to the gas check. The extra metal could strengthen the bullet if the extra lube is not needed, or maybe even make it possible to achieve the accuracy you get now with softer alloys. I believe Larry and several others have written in the past about a certain amount of plasticity being necessary when pushing the limits for the bullet to kind of self-heal against the abrasion of the lands as it moves down the bore. Less lube and a more solid shank could possibly help even things out.

    • #23317
      Harter
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      If you have lube filming with 2 or 3 lube grooves , I think the validation will come not from the front/top grooves but from the bottom /rear c groove . . If it is hydraulic sizing then removing from the forward grooves will reduce the amount of fluid available to size the successive bands . Dip lubing the nose will most likely film size the whole bullet at the speeds and pressure you’re using it might lead as bad as no lube at all.

      The last suggestion would be to coat the bbl rather than the bullet graphite, molly or Teflon dry film lube may or may not help in a zero lube trial. At best it may only keep the failure from sticking to the bbl.

    • #23410
      Anonymous
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      JPHolla;n1257 wrote:

      Maybe he can extrapolate, but I took his clay cylinder example to mean that the rear end of the bullet is shrinking after the bullet impacts the sawdust and mushrooms.

      Not sure how much I can extrapolate because it’s only a vague memory of something I saw but I’ll try. Imagine that a wadcutter shaped bullet is fired at a steel plate. Let’s say the OD of the wadcutter is .500 and the plate has a .460 hole in it. In this fantasy the bullet hits the hole concentrically. The center of the bullet would continue forward sucking the OD down as metal is moved forward. Think back on the video many of us have seen of the million frame per second bullet impacts. The solid lead bullets in particular become anywhere from plastic to liquid on impact. I have no reason to think that sawdust wouldn’t cause some level of plasticity. I’ve seen jacketed rifle bullets, probably Sierra MatchKings, lying on the ground at a metallic silhouette range with the jackets relatively undamaged but a portion of the core has squirted out the hollow point. These bullets didn’t appear to have ever penetrated anything- no gouges on the ogive.

      I’ve also seen lots of cast bullets where steel plate matches are held that have interesting distortions to the base of the bullet. Usually all that’s left is the typical quarter or larger sized splat of lead but the base is frequently concave instead of flat. Sometimes the base would go convex or develop a small bump in the center of a concave base. The deceleration is much more sudden than the sawdust trap but it demonstrated how plastic the metal becomes during deceleration.

      The sawdust probably has a pretty high coefficient of drag and might be slowing the bullets down pretty harshly. I have to wonder what the bullets would look like trapped by water.

      David

    • #23414
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      Water is easy they would look much like those hitting the Buffalo at steel matches . Water is actually fairly dense .

    • #23427
      Goodsteel
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      JPHolla;n1257 wrote:

      Maybe he can extrapolate, but I took his clay cylinder example to mean that the rear end of the bullet is shrinking after the bullet impacts the sawdust and mushrooms. I don’t know if it’s what is happening here, but it seems like a very real possibility to me. We need a medium that slows down the bullet more slowly to prevent any expansion of the nose to know for sure. If it is the case, lube may not be the culprit at all, or at least not entirely. Back to your idea about lubricating only the front groove, I think it’s a good one and simple to try. But I wonder about all the voids back there possibly causing problems if the alloy is not hard enough. I’m really starting to wonder about removing the rear lube groves right up to the gas check. The extra metal could strengthen the bullet if the extra lube is not needed, or maybe even make it possible to achieve the accuracy you get now with softer alloys. I believe Larry and several others have written in the past about a certain amount of plasticity being necessary when pushing the limits for the bullet to kind of self-heal against the abrasion of the lands as it moves down the bore. Less lube and a more solid shank could possibly help even things out.

      The more I think about it, the more this idea bugs me.
      At first, I dismissed it because Larry Gibson did the same test at the same speed and the same alloy, but his target was located 300 yards from the bore as opposed to my target that was only 85 yards away from the bore. Both bullets showed very similar sizing of the base even though my bullets impacted at 2700FPS and his impacted at 1800FPS. I took this as evidence that impact could not be the cause of this phenomenon.
      However, Larry was shooting into wet newsprint that stopped the bullet in only foot or less, and my bullets were fired into wet sawdust that stopped the bullet in 4-5 feet. It occurs to me that this makes it an apples to oranges comparison, and even though both bullets impacted at dramatically different speeds, it might be barely possible that by pure cosmic coincidence, we actually had very similar deformation on the nose (and thus the base) of the bullet.
      Maybe this suggestion isn’t so far fetched after all?

    • #23502
      JPHolla
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      Goodsteel;n1434 wrote:

      The more I think about it, the more this idea bugs me.
      At first, I dismissed it because Larry Gibson did the same test at the same speed and the same alloy, but his target was located 300 yards from the bore as opposed to my target that was only 85 yards away from the bore. Both bullets showed very similar sizing of the base even though my bullets impacted at 2700FPS and his impacted at 1800FPS. I took this as evidence that impact could not be the cause of this phenomenon.
      However, Larry was shooting into wet newsprint that stopped the bullet in only foot or less, and my bullets were fired into wet sawdust that stopped the bullet in 4-5 feet. It occurs to me that this makes it an apples to oranges comparison, and even though both bullets impacted at dramatically different speeds, it might be barely possible that by pure cosmic coincidence, we actually had very similar deformation on the nose (and thus the base) of the bullet.
      Maybe this suggestion isn’t so far fetched after all?

      Yes, I agree with you that equal deformation of the nose would seem to indicate a very similar “negative acceleration” (I can still hear my old physics professor emphatically telling us that there is no such thing as “deceleration”). Did Larry Gibson use No. 2 alloy? How far away can you shoot your trap and keep the bullets in the center? It may give more reliable results. And just to muddy up the waters a little more, if lube is hydraulically sizing the rear bands, it may just be that particular lube. Also, a strong gas check may be able to overcome hydraulic sizing. I’ve often wondered about how gas check thickness became somewhat standardized. I guess they originally made them “just thick enough” to do what most people wanted and was considered so much better than the previous plain-based bullets. I’m surprised no one ever came out with a special high velocity bullet mold with a small check shank to take an extra thick gas check–say .050″ thick for .30 caliber. Maybe they just figured that’s what bullet jackets or half-jackets were for.

    • #23534
      chutesnreloads
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      Not speculating on the cause of the shank shrinkage but thought of a possible way to check if one of you can try it…….Remember reading a few years back about these loooong range varmint shooters(2000+ yards)and them finding their bullets laying virtually unblemished other than the rifling marks. These bullets practically were just falling from the sky at that range.Of course the tester would need access to a place to shoot that far and a rifle with a modified scope mount so he could hit close to a place the fired bullets could be found.Measuring said bullets I would think would answer the question of whether they’re being swaged in the barrel or at impact.

    • #23554
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      The reason why I used the specific components that I did, and shot at the specific speed that I did was in order to duplicate Larry Gibson’s situation as closely as possible. He used Lyman #2 lubed with 2500+, and shot at 2900FPS MV, and I followed suit. The only real differences between the two rifles was the twist rate (Larry used 1-16 and Glenn’s rifle is 1-14 both have the similar length and profile) and the distance the bullets were caught at.
      One of the reasons I am asking for help is that Glenn’s 85 yard range is the only range I can perform this test on easily.

    • #23555
      Goodsteel
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      Absolutely. No question.
      Unfortunately, finding a place in Arkansas where you can both see and shoot over 1000 yards is almost non-existent, which is why I asked the membership for help with this experiment.

    • #23572
      az-jim
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      Tim, your bullet trap appears to have chambers, maybe it just the framing that holds it together? What about progressively varying the medium in the trap in an effort to slow down the bullet more gradually? Start with say shredded paper, shredded cardboard, different densities of various mediums. That would lessen the sudden impact and could eliminate the shrinking base/ expanding nose theory.
      Just thinking out loud, but old T shirts, socks, etc. cut into strips or loosely bunched up could work too.

    • #23594
      Wright Arms
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      I don’t know if this will help or not, but I have a .308 rifle and 2 bullet catch systems. One uses rubber mulch, the other water. If someone were willing to send me similar cast bullets, I am perfectly willing to perform tests and see if the deformation appears to remain consistent.

      This is strictly meant as an offer to confirm or deny, and nothing else. It is a 12 twist .308 barrel on a Mauser action. It’s what I have, and what I’d have to use. The bullets would be captured point blank. I do not know if my systems would be effective at 2900 FPS. I can tell you they work, with interpretation, at 2500 FPS with .35 caliber cast bullets in the 200 grain weight class. I can also tell you all from experience that the deceleration will be rapid and as such, deformation due to impact will have to be accounted for.

    • #23595
      Wright Arms
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      Good heavens. I don’t think I’d live long enough to find a bullet fired to the horizon lying upon Mother Earth. I do good to find my socks in the morning or a shed antler while squirrel hunting. This idea astounds me . . . .

    • #23600
      Goodsteel
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      Wright Arms;n1649 wrote: I don’t know if this will help or not, but I have a .308 rifle and 2 bullet catch systems. One uses rubber mulch, the other water. If someone were willing to send me similar cast bullets, I am perfectly willing to perform tests and see if the deformation appears to remain consistent.

      This is strictly meant as an offer to confirm or deny, and nothing else. It is a 12 twist .308 barrel on a Mauser action. It’s what I have, and what I’d have to use. The bullets would be captured point blank. I do not know if my systems would be effective at 2900 FPS. I can tell you they work, with interpretation, at 2500 FPS with .35 caliber cast bullets in the 200 grain weight class. I can also tell you all from experience that the deceleration will be rapid and as such, deformation due to impact will have to be accounted for.

      That’s a very generous offer! I would like to take you up on it. All I need as an address and I will send you some bullets from the original test, lubed and ready to go.

    • #23633
      popper
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      Interesting results with the different powder burn rates. Faster gives less deformation? Plasticizing pressure applied for a longer time with slower powder? I’ve recovered the remains of one cast rifle bullet, only part was in the GC and it ‘looked’ melted but was very weak. IIRC it was 4% Sb alloy, 2400 fps in 308W. It cut through 12ga steel wire and was recovered at the front of the rock pile. I’ve recovered 40SW shot into a rock pile from ~7 ft. 95% wt retention and the bases were not cupped at all, they had the swaging ‘skirt’. I understand the ‘noodle’ principal but reject that as the shrinking phenomenon. Both had very rapid deceleration.

    • #23636
      Goodsteel
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      popper;n1692 wrote: Interesting results with the different powder burn rates. Faster gives less deformation? Plasticizing pressure applied for a longer time with slower powder?

      Actually, we observed no difference due to pressure. The only thing that seemed to effect it was speed.

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