ar 15 cast loads intell?

[nicholst55]

Here's some info: http://castboolits.gunloads.com/show...st-Bullet-Test

[picaresque]

I've been working on cast loads for semiautomatic rifles for a while now. I was inspired by BruceB's thread that is a sticky at the top of this forum. I encountered issues unrelated to the cast bullets in my M1A -- I subsequently found out that this rifle did not like hard primers. Given the issues with the M1A, I moved to working up a similar round for a Ruger mini 14, and later an AR15.

To begin with, I would not try to push a cast bullet at speeds approaching 2,000 feet per second out of any rifle without using a gas check. As you know, cast bullets have a speed limit of around 1900 fps that can be broken by using gas checks. Even with gas checks, cast bullets will lose accuracy at a certain point. This point will vary from rifle to rifle, and on other factors, such as bullet weight, powder type, etc.

I read on one of these forums that a good starting point was to find data for a jacketed bullet of the same weight, etc., using the powder desired, and start at sixty percent of the maximum load for that jacketed bullet and powder. I happened to have good luck with IMR 4895 -- I also happened to have several pounds of it on hand, so I started with that load. I then worked up from that mark at half grain increments to the point that the rifle -- in this case, the Mini 14 -- functioned reliably. I then worked up from there, again at half grain increments, watching the groups tighten up -- until they began to open up again. I figured I had reached the accuracy limit I had read about. To wring the most accuracy from the round, I then worked up from the load that had produced the best group, this time at increments of one tenth of a grain. My optimal load for the Mini 14 was using a RCBS 55 grain spire point bullet cast in air cooled wheel weights and lubed with a home concocted bullet lube, sized at .225 with a gas check, over 17.5 grains of IMR 4895, set off with a TulAmmo small rifle primer. I used military grade LC brass. At the time the TulAmmo primers were the only ones I could get.

I subsequently obtained an AR-15. In experimenting with the above load, I concluded that a direct impingement AR action needs more gas to function than a gas piston powered rifle like the Mini 14. My optimal Mini 14 round turned the AR into a single shot rifle. Working from the 17.5 grain Mini 14 round, I found that the best round for the AR required 19.0 grains of the same powder, with all other components being identical.

Shot through a later model Mini 14 Ranch Rifle, the 17.5 grain rounds choreographed consistently at slightly over 1900 fps. The 19.0 grain loads choreographed through the same rifle at around 2050 fps. Accuracy was roughly the same for both rounds.

Of course, your mileage may vary.

[Harter66]

I shoot a NOE 225-55 @62gr in the AR I shoot with a 1-8 twist at 2050 fps with H322 . It matches basically jacket groups with assorted factory 55 gr FMJ .