Thanks for the very informative replies!

I have been pondering the 'goings on' when a cast bullet is fired. It would be subject to the most stress during initial acceleration and entry to into the rifling. That would be good if the bullet is 'upset' and swaged to fit the bore and maintains a uniform shape around it's axis of symmetry. Then it would be subject to some heat, smearing effects and a tendency to 'lean' to one side in the bore under influence of gyroscopic forces. Then there might be gas blow-by between the grooves and the bullet which would flame cut the bullet, making it less symmetrical for it's flight through the air. In the barrel, the base of the bullet would be under stress which will cause it to swell into the bore, increasing friction and hence the smearing effect. The 'upsetting' stress might cause the bullet to deform unevenly into the lube grooves. Then, as it leaves the bore, depending on the level of pressure behind it, it could upset a little. Then it still has to contend with gyroscopic forces which may or may not cause the bullet to swell - remembering that the bullet is now hot and may be somewhat softened.

I must say I do feel the reference to jacketed bullets is relevant here because the effects of spin rate and bullet shape/construction/ internal and surface defects might be greater than with jacketed bullets but the effects of spin rate on an imperfect bullets could be of interest to us but the jacketed bullet would show this without the clouding of bullet deformation/damage being added to the mix.

How does that sound so far? Have I missed something or got it all wrong? (Or maybe just some of it). Please add corrections and/or additions.
Thanks.

(Hope I am not boring you folks).

quote:

Originally posted by waksupi:
Hi Guys, Don't check in here too often, but do find interesting things when I do.

Joe, you have my shooting of long projectiles at higher velocities, somewhat out of context. When I was doing that particular experiment, I was attempting to shoot pure tin bullets, at factory + velocities. This is where the bending came in.
I can not say what an alloyed bullet, at various hardnesses would do, when shot at those speeds.
Indications with the pure tin, was the bullets were indeed being twisted out of shape, as they left the the muzzle, resulting in at least a 15 foot pattern at 50 yards, and who knows what at 100.

Hi Rick,

Sorry about my half truth. At any rate I still don't believe it. Bullets going into a snow bank at high velocity isn't a good test. Now if you were standing in the center of a one foot deep big pool of water about 500 yard circle and shot straight up into the air and recovered the bullets at they dropped into the water and they were bent, then I would believe it.

Thanks for taking time to clarify what you said.

Joe

Joe, I must go back to the fact, that there was extreme dispersion, at fairly close range. Would you have a suggestion of what caused this, if not the bullets deforming?

quote:

Originally posted by waksupi:
Joe, I must go back to the fact, that there was extreme dispersion, at fairly close range. Would you have a suggestion of what caused this, if not the bullets deforming?

Rick, my first thought is that if indeed this did happen, that is the bullet bent right at release from the muzzle or there after...that it is the cause of using pure tin for the bullet. I know it doesn't happen with normal bullet alloys. You know I done a test with soft air cooled weights using a 70 grain bullet in 22 caliber. That is a mighty long bullet for diameter just as is the 6.5 bullets you used. I shot those over 3000 fps from a 1-7 twist HBAR AR15 and none of them dispersed such as your bullets. Explain that to me? That is a more drastic test they your test. I'll bet you weren't even close to 3000 fps alone over.

Joe

I also believe they deformed at the time they left the muzzle. I do know the recovered bullets weren't deformed from landing in the snow. I've recovered too many bullets from snow banks, and the tin ones were of a distinctly different shape, and consistant in thier form.

quote:

Originally posted by waksupi:
I also believe they deformed at the time they left the muzzle. I do know the recovered bullets weren't deformed from landing in the snow. I've recovered too many bullets from snow banks, and the tin ones were of a distinctly different shape, and consistant in thier form.

Let me ask you this Rick. The recovered bullets, did they have good rifling grooves on them? Do you remember what your bore looked like after firing them? The reason I ask is because as many casters know that too much tin in your alloy causes leading/tinning of the bore. The proper amount of tin is a good thing. I think your bore got really tinned up and if it did there is no way those bullets would have gotten spun correctly. Do you remember your velocity? If I can get some tin I'll cast up some 6.5 for my 6.5 Grendel with the 8 twist and we'll see what happens. I can tell you alreay that with the correct alloy they shoot better then good when pushed, no bending, no flying way off the target.

Joe

Joe, that was a long time ago, and I don't remember all the details. I do not believe the bore showed any metal fouling, though. Since I only shot five rounds, and none hit the target, the bore would have had to tinned seriously at the first shot. I believe I was loaded to a level of around 28-2900 fps. They were my first attempt, and after the result, I didn't shoot anymore. Still have the keyholed imprint through my entry way of the cabin.

quote:

Originally posted by waksupi:
Joe, that was a long time ago, and I don't remember all the details. I do not believe the bore showed any metal fouling, though. Since I only shot five rounds, and none hit the target, the bore would have had to tinned seriously at the first shot. I believe I was loaded to a level of around 28-2900 fps. They were my first attempt, and after the result, I didn't shoot anymore. Still have the keyholed imprint through my entry way of the cabin.

Wow on that keyhole in your entry way. I'm glad you didn't get hurt somehow from that. I have a friend that works for Lothar Walter barrel manufacturer. He happens to be cast bullet shooter too. I mentioned your test and results. He asked what possessed you to try shoot a tin bullet that fast or even shoot tin as an alloy. He thinks the bullet stripped through the rifling.

Joe

Rick,

More to answer your 6.5 Swede tin bullet incident. Here's three things that overstabilizing a bullet can do: 1. Varmint bullets with thin jackets can literally rip apart in flight if the twist rate is too fast, 2. The effects of a flaw within the bullet are magnified and groups open, 3. The bullet "goes to sleep" farther from the muzzle. We want to talk about number 3 in your case. Number three relates to a known characteristic of spin-stabilized bullets--they "wobble" slightly as they leave the tight confinements of the rifled bore. Spin eventually corrects the wobble, usually in the first 50 to 80 yards, and the bullet settles into stable flight, or informally, it "goes to sleep." However, long bullets fired at high velocities from fast-twist rate barrels may not go to sleep until more then 100 yards from the muzzle.

I suspect this may be the case in your tin bullets. They are long for caliber and you shot them very fast from a very fast twist rifling.

Joe