Question about reloading for an M1A.

L308 · Feb 7, 2022

I have a question for those of you who shoot an M1A:

I have a Springfield Armory M1A I would like to start reloading for. I understand reloaded M1A ammo should use military grade primers, which are harder than commercial primers.
Those primers are hard to come by at this time.

I believe the harder than normal primers are needed to prevent out of battery slam fires due to the design of the M1A firing pin.
I also understand the seating depth of primers is very important in this firearm.

My question is this:
Do you M1A owners have any experience with this problem? Have you been able to use either commercial or reloaded ammo without using the harder than normal primers?

Thanks for your help.

ron · Feb 8, 2022

I reload for my M1 and M1A using standard large rifle primers, Winchester, Rem. or CCI. I use a primer
pocket uniformer to prevent a 'High Primer' from causing a slam fire. Standard Full Length RCBS dies.
Adjust the sizer die to bring the shoulder of the case to what factory ammo measures. RCBS precession
Mic or a Hornady Bullet Comparator are the tools that can do this. Good brass, 168 SMKs and IMR 4064
will produce excellent accuracy.

gmerkt · Feb 8, 2022

I've reloaded and fired off fair to say several thousand rounds in several M1A's. I'm down to just the one now. Never had any issues with any type LR primer I've used. I prefer CCI brand but have used WW and S&B. I've never had issues with primer pocket uniformity for the service grade ammo I make. I've chosen to use RCBS small base dies just in case, but at one time I also loaded the same round for an Armalite AR10. I've mostly used IMR 4895 at Service Rifle recommended charges, mostly with 168 gr. HPBT bullets. When I downsized and simplified things over the past few years, I settled on Hodgdon BL-C(2) but I haven't fired off all that many of those yet.

Brass thickness varies some between commercial .308 Win. and military 7.62mm NATO cases. You might find that a slight sizing die adjustment is needed when you change from one to the other. You can check this out with the cartridge headspace gauge. I really don't want the bolt to have to bump every over-length case into spec.

Rifles with a floating firing pin, like the M1 Rifle and the M1A, and most of the AR's, if you chamber a live round, then do not fire it and eject it, you will see a faint dimple in the live primer. From the interia of the firing pin bouncing off. And that will happen every time a round gets chambered, it's just that you usually fire them off and never see what I'm talking about. It just is. My AR10 had a spring on the back of the FP that prevented this, but every other of the many AR's I've owned didn't.

My preference for CCI primers is, they are supposed to have the hardest cups in the industry. Even the standard. If you want a little more margin, you get the CCI #34's. As I said, I've never had any issues with softer primers, but like the small base dies, the harder primers appeal to me as another matter of just in case. Now that I've switched over to Hodgdon BL-C(2), a ball powder, I've also switched to CCI LR Magnum primers, and these have thicker cups than non-magnum. Supposedly CCI has said that #34's are the same as their LR magnum primers, but don't have the nickel plating.

Pepe-lepew · Feb 8, 2022

LR primers are fine. Seat primers to bottom of pocket like normal.

Slam first risks are increased with single loading when you throw a round in the chamber and release the bolt from full stroke. If you load singles, ride the bolt about half way closed and then release it.

A very common M1a load is 41.5 gr IMR 4895 with 168 gr match bullets. If that load does not shoot good there is something wrong with you or the rifle. It is mild so I load it in both military and commercial brass but only shoot one head stamp at each match.

Load data, Load data

Military brass is thick and heavy but there is some commercial brass just as heavy. Hornady has multiple headstamps of 308. Some light, some heavy. So be aware you can't mix brass especially at max loads and don't assume commercial brass has more capacity.

ma96782 · Feb 10, 2022

I use to shoot hi-power matches using my M1A.

Back then, I loaded once fired surplus military LC brass (or Match LC cases), Fed 210 primers and 748W with a 168 grn BTHP. I full-length resized and did NOT anneal. Making slightly more than 100 rounds at a time, for my lot.

BTW, along the way there would be some case separations. So, I probably only got 3-4 reloads before I dumped the entire lot.

Aloha, Mark

ma96782 · Feb 10, 2022

Notes: Slam fires.

What CCI says..........

CCI® No. 34 and No. 41 MILITARY RIFLE PRIMERS

Military-style semi-auto rifles seldom have firing pin retraction springs. If care is not used in assembling ammunition, a "slam-fire" can occur before the bolt locks. The military arsenals accomplish this using different techniques and components—including different primer sensitivity specifications—from their commercial counterparts. CCI makes rifle primers for commercial sale that matches military sensitivity specs that reduce the chance of a slam-fire when other factors go out of control*. If you're reloading for a military semi-auto, look to CCI Military primers.
*Effective slam-fire prevention requires more than special primers. Headspace, chamber condition, firing pin shape and protrusion, bolt velocity, cartridge case condition, and other factors can affect slam-fire potential.

Aloha, Mark