What is different about loading for an AR?

[Jack Ryan]

Other than needing a harder primer and making sure the bullets won't move as they cycle through the action, is there anything I need to know about loading for an AR vs. the same cartridge in a bolt gun?

No, nothing.

 

[Varminterror]

Bending operating rods - notably in the M1 Garand - is not the only problem deriving from too enthusiastic operation of a semi-automatic arm. There are a number of other parts and connectors which will fail from breakage or accelerated wear.

...None of which have anything to do with the use of slow powders in AR’s, which was your original (invalid) point I was refuting.

 

[misser]

i and one other guy i know have had problems with bullets moving out of the brass when the bcg picks up and slams the cartridge's into the chamber .i with a 708 he with a 308

 

[Blue68f100]

Try a different mag. Reduce the size of your expander to tighten up the neck tension.

 

[Kaldor]

Other than needing a harder primer and making sure the bullets won't move as they cycle through the action, is there anything I need to know about loading for an AR vs. the same cartridge in a bolt gun?

Some good and bad recommendations here in this thread.

Harder primers: No. Ive shot 10s of thousands of Federals, CCIs, and Winchesters, and never felt the need to use a CCI 41. I have loaded some loads FAR above what the book says, and while I will see pressure signs, Ive never pierced a 400 or had one blow out. The floating firing pin is cause for worry, but if you want to see how bad is really is, drop a round in the chamber with the bolt back and sling shot it home. There is NOT enough indention made to ignite the primer. If it was, you would be sure that every manufacturer in the world would use a 41 as insurance against this, and they dont. The old Remington primers (cant recall the number) that were not for high pressure. Yes, those had a bunch of issues with being run by people in 223, even though the box said not to, but you cant fix stupid. The other cause for concern with a 41 is that they will hide pressure signs because they are thicker that you would normally see in a standard primer. This leads to a situation where everything looks great, but suddenly youre blowing primers from the brass or tearing stuff up. Short version? Buy standard small rifle, seat them below flush, stay within the pressure limits for those, and you will be fine.

Small base dies: Not generally needed. Most ARs will chamber a standard sized case with no issues. The only place where you might see a need for a small base die is if the manufacturer uses a tight chamber. One thing that will get people thinking they need a small base die is when they dont size enough, as in they dont bump the shoulder enough. You need to size 223 ammo to full cam over on the press, as far down as the ram will allow. The one thing SB dies will do is work both you and your brass harder. It takes extra force to size with a SB die, and that means you need to work harder as well. There are some exceptions to this rule as personally I have some very specific loads for my 6 AR, where I only bump 5 thou on the shoulder, but those are only ever shot in that gun, and I keep the chamber spotless. Short version: Buy standard dies, set them up correctly, and only buy small base if you need them.

Powders: Pretty much anything from 4198 thru Varget is a good choice. You can easily check a burn rate chart to see what falls into that chart for other manufacturers. I prefer 8208 XBR for heavy bullets (68-77gr) as its a temp stable powder that doesnt spike pressure easily and can get a high load density yielding good velocity and accuracy. For my blaster ammo like 55s and 62s, I prefer a ball powder like H335 or AA2230. Varget is a good choice however you can struggle to get velocity out of it as Varget is a chunky powder that eats up alot of case space and it doesnt flow worth a dang from a rotary drop. I like to also stay with powders that will drop with some degree of accuracy so I can use a rotary drop, whether its on the progressive, or on the bench.

Crimp: Some say yes, some say no. If neck tension is perfect, no. If you use a light flare like from a Lyman M-die to facilitate easier seating of flat base bullets, yes, and just a kiss from a Lee FCD to close it up. I have seen no real difference in accuracy with a light flare closed up with kiss from a FCD over chamfering every case. Do I chamfer and deburr 223 brass? Yes, but only on very specific loads where Im tuning accuracy as much as possible. The Lee FCD is a fantastic die, however do not over crimp as it will effect accuracy. Like I said, just a kiss. Taper crimps work too, but are extremely dependent on the OAL lengths of your cases being all the same.

Trimming: Yes, every firing. With an electric trimmer like a Worlds Finest Trimmer set at the correct length, it will take you less time to just trim them all whether or not you trim anything, than gauging all your brass.

Crimps: Do what you want. Some guys swage, some guys cut. Its a one time thing, and needs to be done even on alot of commercial brass. I have used the RCBS cutter for years. Pick your poison.

Brass: If you can swing it, try to find some Lake City brass. Its fairly consistent from year to year, and it lasts and lasts and lasts. I know I have a bunch of LC with over 10 firings. If not, go with whatever you can find, just be aware that using cases from different manufacturers is going to effect accuracy. Also, LC brass has the same internal volume as commercial brass, so dont let anyone tell you different. That is only true for LC 7.62 brass vs commercial 308. One thing to keep in mind is as you get more and more firings on a bottleneck case, your neck tension is going to get lighter and lighter, and eventually youll see spring back post sizing and your bullets will either fall into the case when setting them, or fall out in your ammo can. At that point youll either have to junk it, or start annealing.

 

[MEHavey]

I'm not sure what the common primer for 350 Legend is, or what it was designed for.

Any small rifle in bolt actions, CCI#41s in my ARs
Also, run at same pressure as 223/5.56, so same primer pocket life
350s have a short throat, so the throat/ogive match-up drive OAL