Crayola of Death innaccuracy theory

[Dolomite_Supafly]

So I shot some of these into some media to check to see if the bullet is skipping over the rifling. On the bullets that did not completely mushroom the rifling marks look fine. No signs of the bullets skipping over the rifling. So I do not believe that is the cause. Another BIG clue the bullets are not skipping over the rifling is the fact they are stable and hitting the targets square without a single keyhole in a lot of rounds fired.

So what do I think is causing the inaccuracy?

I think that the centrifugal force is slightly bending the bullet tip off to one side. Not enough to cause the bullet to become unstable but enough to open up the groups substantially. And I believe the tip begins to bend but at some point the bullet is too thick for it to continue to bend over. And this is only made worse when feeding causes the tip to bend.

The reason I think it is bending is the bullets I shot into the media mushroomed in an oblong way. Even though the bullets were hitting the media square the bullets were mushrooming like they were off center. The bullet bases were where they should be and were facing back at me, like they should be, so I know tumbling is not causing the oblong mushrooming.

And another BIG clue is these are doing great in guns with slower twists. We have several people who have pushed this bullet well beyond 300 Blackout velocities and having great results. I know that when I shoot these in my 10 twist guns the groups are smaller than with my 8 twist guns.

To test this I am going to load up some bullets and then use a pair of wire snipes to take off some of the tip to see if the accuracy improves. I suspect the accuracy will improve but I am not sure how much of the tip I need to remove.

On a positive note these bullets mushroomed out quite well and retained a lot of their weight. They started out at 130 grains and all bullets recovered weighed in at 112-113 grains. And even when loaded down to ~1,100 fps they still mushroomed out to .45". I figured it would have passed right through but it acted like any jacketed HP I have shot.

If it turns out the bullet tip is too thin I am going to take a chance and drill mine out to a thicker dimension.

I do know Swede is experimenting with making this bullet with a thicker tip.

[yondering]

I think you're right, although I'll add that the deformation starts during feeding. I think this same design, with the nose truncated with a .060-.080" meplat, would shoot a lot better. It wouldn't have to be a flat tip though, it could be a 30-45* cone, or even a round tip, which might be the best, since a round nose is the most resistant to feed damage.

When I get around to it I was going to cut the noses of some of these in my lathe to see if it helps accuracy.

[Dolomite_Supafly]

I told GDS in a PM that I would rather have a round nose than a meplat on the one Swede is working on. He basically took .20" off the nose and it looks pretty good.

I think the nose bending is also why it is so random. Depending on the velocity and the alloy the nose bend could be slight or very dramatic. Couple that with the fact some might be perfect enough not to bend at all and it can be very frustrating.

Maybe it is just not a 300 Blackout bullet, or at least not a 8 twist bullet. I am actually going to build a gun around this bullet eventually. It will probably have a 12 twist barrel.

Hope he doesn't mind but here is what Swede is thinking:

It would be easy to do with the cherry he already has too.

[pvanwagner]

How is the accuracy in a Handi Rifle or bolt gun fed one at a time?

[Dolomite_Supafly]

How is the accuracy in a Handi Rifle or bolt gun fed one at a time?

It depends on velocity. The higher the velocity, or twist, the worse the accuracy.

Even in a 10 twist the accuracy is pretty bad at max velocity but keep the velocity down and it actually shoots really well.

[NordicG3K]

Do you know if Swede will include a hollowpoint option with this new design?

[Dolomite_Supafly]

No clue if he is even going to do the new design. He is just looking at options.

[popper]

You might try it with a 3R tangent ogive & small meplat. Gives more strength in the nose & good feeding. I'm having trouble coming up with a 4R under 150 gr. that is close to 1" long. Wish I had't got rid of all my drafting tools. I got my 150 PB 2R ~1800 with decent accuray, planning on changing to 3R for better feeding, but would like to get it down to 140 gr. probably reduce the front band length & increase the boolit length. I'm not finding the 0.18 meplat to be a feed problem. Honed out a new extension to take the 2R nose, 3R should not be a problem at all. The 2R works great in the 30/30 with 2400 but uses a lot of filler so I get some vertical stringing. May try some slower powder when I can find it.

[excess650]

I sent a batch of cast bullets to a guy in Ky to try. Among them were CODs sized .311" and conventionally lubed. He indicated that his best groups (1.5" at 50 yards)were over 14.6gr H110 with 2.10" OAL. I didn't ask the twist, but it was a gas operated pistol.

I have intended to "shorten" some of these and see how much length needs to be removed to make them more accurate, but other priorities have gotten in the way. I did shoot some with ~.100" meplat (snipped with toe nail clippers) and they produced less flyers and considerably tighter groups than those that weren't shortened. My suspicion was that we weren't going to see a consistent burn from the powder without resorting to something quicker (2400). 16-17gr 4227 shot sub 2" at 50 yards from my 16" with a red dot, but that same rifle will shoot Lee 155s into "cover with a nickel" groups regularly with the same red dot.

I had also PMed Swede to see if his existing tooling could be modified to create a shorter bullet with wider meplat.

[yondering]

Hope he doesn't mind but here is what Swede is thinking:

It would be easy to do with the cherry he already has too.

Interesting, although the nose is on the edge of being too large for best accuracy, IMO, unless that tip was changed to a RN or a blunted point. As it is, the sharp edges of that flat nose will see some feed damage in many AR rifles.

Personally, my only interest in a lightweight bullet light this is for full power high velocity loads; a design that can't handle full velocity, with the standard 1:7 or 1:8 Blackout twist, is useless to me.