M1A Reloading Suggestions

[jelenko]

I have found Zediker to sometimes write about topics he is ill informed about.

Danny

Same here. Can't remember specifics, but I remember a couple whaaat? reactions.

 

[danny]

Same here. Can't remember specifics, but I remember a couple whaaat? reactions.

Mostly it was in regards to the mechanics of rifles.

Danny

 

[257Roberts]

Hey folks, thought I'd give an update. i sure appreciate all the comments & suggestions.
I haven't been back to the range yet, but I did do some measurements.

I do full length size everything I own, I don't even own a neck die. The closest I have to a neck die is some bushing full length dies that I use on my long range match rifles. In this case however, my standard Forster 308Win FL die screwed down touching the shell holder makes the shoulder length 1.630" with a Hornady 0.400" datum bump gauge. Its very accurate a repeatable.

As poor as the technique may be, I did the soft seated spent primer method to try and "zero in" on a chamber length in my M1A NM. Using several pieces of NEW short brass and doing several types of bolt closings [hard slap, light slap, manual push] I get a primer to shoulder datum length of 1.629"-1.630" every time.

For what its worth, SAAMI 308Win headspace length is listed at 1.630-1.640.
The case datum length is listed at 1.634-.007.
I am not sure if 7.62x51mm is slightly different than that, but I believe the M1A is chambered in 308Win regardless.

So my next attempt will be to take out reloading press overtravel some and get the shoulder length down into the 1.625" range and try again.

Also, I did purchase some Federal Gold Medal Match 168gr factory ammo, Springfield Armory's recommended food, and first thing I did was measure the datum length on a box of those. Every one is 1.620", or 10 thousandths short of SAAMI minimum chamber length.

 

[fatelvis]

I can tell you that if you are conscious of bumping the shoulder .003-.004” only when reloading for the M1A, your brass will last much longer than three or four uses. When I started reloading, (30yrs ago), I would full length size, having the shell holder touch the die. I wasn’t much for measuring results back then. I got head separations after only two firings, using moderate loads in competition. now that I am careful to size only what is needed, my brass lasts as long is I want. I usually throw it out because of beat up rims after four or five loading, not because of head separations. By the way, I only use Lake City brass when loading for the M1A, it is much more durable than others.

 

[Bob3700]

Fatelvis is right on. Factory ammo is loaded so that it will chamber in any 308 rifle. So the base to shoulder is definitely short. When loading for my M1A, I would measure several fired cases (base to datum) and use that measurement as the "Zero" or chamber length. For rapid fire loads, bumping the shoulder .003-.004" worked great. This was with LC Match brass. I can't tell you how many reloads I had on my practice brass. Maybe a dozen using this method.
For match use, where you need 100% reliability, I would use newer brass with only a few firings on them.
The more you push the shoulder back, the more the brass stretches and the shorter the brass life.
Bob

 

[Mad_Charlie]

Fatelvis is right on. Factory ammo is loaded so that it will chamber in any 308 rifle. So the base to shoulder is definitely short. When loading for my M1A, I would measure several fired cases (base to datum) and use that measurement as the "Zero" or chamber length. For rapid fire loads, bumping the shoulder .003-.004" worked great. This was with LC Match brass. I can't tell you how many reloads I had on my practice brass. Maybe a dozen using this method.
For match use, where you need 100% reliability, I would use newer brass with only a few firings on them.
The more you push the shoulder back, the more the brass stretches and the shorter the brass life.
Bob

"I would measure several fired cases (base to datum)"

You also may want to consider turning off the gas and cycling manually to avoid case stretch due to extraction.

 

[searcher]

As your concern is whether you have enough shoulder setback is the concern - I'd simply measure a few fired cases that did go "bang". If they are not measurably longer (from shoulder to base) than before being fired - that probably is your situation. It they were, say .002" or more longer than before being fired - you know there was clearance when they were fired. You can also simply load a cartridge into the chamber (off the magazine - to be safe), then extract it by pulling the bolt back and ejecting it (without firing it). Re-measure the length. If it is shorter than before loading - that is also an indication that your shoulders are too far forward - as the bolt attempting to close will push the shoulder in a bit. I know from experience that ammo head spaced over .002" long can and will chamber and fire as the necks get pushed back when it locks up. Even easier in an AR-15.

 

[searcher]

I have found Zediker to sometimes write about topics he is ill informed about.

As we know - there are exceptions to everything when it comes to many aspects of reloading and gun part specs, longevity, etc. Zediker's stance of "this is the only way it is" leaves many of us shaking our heads - as "we know betta"

 

[dc.fireman]

Glenn Zediker Obituary

A small base sizing die helped me immensely with the NM M1A - no more failures to feed.

My load for it is a Nosler CC 168, IMR3031 @ 39.5gr., LC Match case, CCI 34 primer. I anneal the cases on the Annie, and toss them after the 4th firing, because the rims are pretty beat up. YMMV.