AR Platforms and Brass

[OnlyDans94]

I use commercial brass for all of my match brass and 100% prepared LC brass for shooting where the brass may get lost. If you use LC suggest you buy processed brass but still check the LC to make sure the primer flash hole is centered in the primer pocket.
Most of my match AR guns, that are based on 223 cases, I use sorted nickel plated match brass in. Been building ARs for a few decades, since the 101st sent me to the 3rd Army school in 1964.
If you run across one, the 6mm Mongoose is an interesting AR-15 rifle cartridge. Is designed to use LC brass, trimmed .050 shorter, fire formed, body blown out with a 40 degree shoulder to use 80-95 grain 6mm bullets at 3,000 fps. A guy from FL designed it to have 32 grains of water capacity and to use 223 mags.

now this is some advanced loading lol, im quite a ways away from doing that

 

[OnlyDans94]

LC brass is always a solid choice for either 223 or 308 in an AR platform.

I have gotten better life with LC cases in 308 compared to 223. I would say I average 4-5 firings in the 223. In 308 I have fired cases up to 9 times in 308. There were fairly beat up but I think I could have fired them 2-3 more times if they were annealed. They had seriously work hardened at that point.

I have not noticed any difference in case life or accuracy with LC vs more expensive brass in AR's.

The most important point for good case life in semi autos is DON'T LOAD HOT. That will lead to loose pockets and case stretching much more rapidly than in a bolt gun. For example, the 308 LC brass that lasted forever was primarily shot with a moderate load of 41.5 gr IMR 4064 under a 168 SMK.

I would highly recommend looking up specific semi auto load data. Good sources are Hodgdon's service rifle, Sierra's AR manual, and Hornady's AR-specific 6 ARC data.

I also shoot an MWS and MK12 clone. You will be likely be able to achieve excellent accuracy from both of these.

thank you! When the books say service rifles, say like hornadys manual, to my knowledge it seems that they are talking about the M14, at least for the 308. Will that same data apply to the AR-10?

 

[RabbitSlayer]

I was under the impression that ARs required more sizing like .004 and that .001/.002 was more for bolt actions. Do you recommend .002/.003 even for 556/762? Or is this in reference to when i load my 6mm ARC AR?

I sure would not take .001 headspace clearance into combat. For all other use .002 should work just fine. I go .003 on my gas gun, only because I have measured headspace on batches of 500 sized cases, every single one. There are always a few that are long or short with the majority being on the money. I think last batch 3 pieces were .002 long which is zero clearance in my bolt gun. They close with the slightest resistance with a stripped bolt. In a gas gun maybe those 3 wouldn't close, especially with a fouled chamber. I anneal every time too. I sized those 3 again they still didnt move. Not messing with my die for 3 pieces. Guess they are either thicker or harder and spring back more.

 

[mic2377]

thank you! When the books say service rifles, say like hornadys manual, to my knowledge it seems that they are talking about the M14, at least for the 308. Will that same data apply to the AR-10?

The service rifle load data is in theory for M1 and M1a rifle, but will improve brass life and wear/tear on the gun for other semi autos.

AR-10's themselves can handle stout loads. The problem is that they will often times beat, bend, or swipe the brass into oblivion with those in a manner which seriously reduces case life. Heavy bullets and slower powders are the highest risk for this.

 

[rlporter507]

I set back with .002, using lapua brass in my SR. functions fine in the Wylde chamber that white oak does.
im not loading a hot load, 2750 for short range and 2650 for mid range. my 80.5's are loaded .010 off the lands. several of my fellow competitors have had problems with starline brass coming apart, ive never tried it. i switched from winchester to lapua because of the neck wall consistency was much better. so is norma brass which i use in a match rifle. LC brass is thicker, and the lot i had measured wasn't very consistent in neck wall thickness. some say lapua brass is to soft for an ar, but i get 10-12 loadings easy with it then the primer pockets get a little to easy to prime, so then it goes in the bin.

 

[jpjulian]

thanks for sharing your experience, what length do you load the 80gr to?

I'm out of the country so am away from my notes but I loaded .020"-.030" off the lands with a new barrel and left it there for the life of the barrel. That was about 2.440" give or take with a Wylde chamber.

 

[Coyotefurharvester]

I set my die to size to the 0.001 below the low step on my ammo checker. Most new brass, new ammo I have checked with same ammo checker is 0.004-0.006 below the step. I size for best functionality (loading and unfired unloading) while hunting at night in the winter. No stuck rds, no forward assist (a couple uppers don't have one) and no need to use a light to make sure rifle is in battery. I haven't had any brass separation, some of my brass has been reloaded many times. I use range brass(no small base die) RCBS 223 FL die and commercial brass(purchased new). For accurate, functional hunting rds this works well for me. I also run rds loaded same way for prairie dogs.

 

[jelenko]

I was under the impression that ARs required more sizing like .004 and that .001/.002 was more for bolt actions. Do you recommend .002/.003 even for 556/762? Or is this in reference to when i load my 6mm ARC AR?

The idea for more headspace on brass used for AR 15's is to help with feeding.

That said, I've reloaded over 100K rounds of 223 all with headspace of .002 or less and have NEVER had a feeding issue.
I've even gone through a couple hundred that were + .006 with no issues at all - the force/energy in the action spring/buffer/bcg is enough to resize the case.

All that said, I clean my chamber after every 50-100 rounds.

My guess is that the extra headspace that's recommended is in case the shooter allows build up of soot in the chamber.