The Components of Going Faster

[Bigslug]

The only thing I can come up with is that I am on the edge of rotational stability.

My coworkers say that about me all the time.

I am still considering a slower twist barrel so my quest is not over

That's kinda where I petered out on this project since for me cast bullets are largely a means to the end of practicing with cast in existing rifles that I have to hunt with using Barnes. It seems a 3000 fps barrel for jacketed is not a 2500 fps barrel for cast.

Perhaps I need to look deeper into this topic of coppering your casting alloy. That science may be just a little TOO weird.

But at least I have the warm glow of accomplishment from having launched what is now a 7 page topic.

[charlie b]

LOL, yep.

FWIW, I do not see a copper alloy doing any better. My theory is the inconsistencies in the cast is what causes the RPM problem. Adding copper to the alloy would not change that.

Sometimes I wish I could try swaging with hard alloy lead. But, if going that route then why not just get some jackets and make 'real' bullets A long time ago I made some solid copper bullets. They worked well but were very time consuming to make. We made up some tooling for the lathe (father-in-law was a screw machine operator) and it went a little better. Maybe a good CNC these days would work ok.

That stuff is just not in the cards right now for me. I am kinda happy with 500yd performance so will just stick with it until I decide to rebarrel.

So, yeah, the short answer is to match the twist rate to what you want to shoot.

[Larry Gibson]

charlie b

"The only thing I can come up with is that I am on the edge of rotational stability."

Just as long as you're not under that edge. On or close to the edge is a good place to be if shooting longer range. Reason being is the rotational velocity decrease very little over 1000 yards as compared to the velocity loss. If the bullet is stable at 100 yards, it will remain stable through its practical flight range.

Also, we must keep in mind the adverse effects of exceeding the RPM Threshold have nothing to do with the bullets stability.

[charlie b]

Agree on both counts. I should have said on the edge of the RPM threshold. All of the bullets that 'spiral' out due to the RPM issue hit the targets cleanly, no sign of instability.

[Larry Gibson]