Proper sizing for M1a and Garand

[fatelvis]

Trying to achieve a .003" shoulder bump for these two rifles, I fired a few rounds in each with the gas system off (M1a) and gas plug remover (M1), hoping that this would give a more accurate depiction of actual chamber size. Would setting up my sizer to bump these Cases' shoulders back .003" be a good idea? I'm trying to avoid disassembling the rifles, and checking with a stripped bolt, because they're both bedded. As always, thanks guys!

 

[10XSHOOTER]

Use a small base die and push everything back. they'll feed better

 

[Doug Beach]

Measure the head to shoulder on a small handful of fired cases, no need to turn off the gas. From the case with the shortest dimension, set your bump an additional .003”, using a small base die. Done.

 

[fatelvis]

Use a small base die and push everything back. they'll feed better

I've FL sized them in the past, without using a SB die, and was experiencing complete case head separations after two firings! I just ran my M1A's "test pieces" through my Redding Instant Indicator, and they showed being all about .010" over the SAAMI guage they included with the die. I'm trying to only size my brass enough to minimize case head seperation, and try to at least reach the hailed "four firing limit".

 

[Doug Beach]

I've FL sized them in the past, without using a SB die, and was experiencing complete case head separations after two firings! I just ran my M1A's "test pieces" through my Redding Instant Indicator, and they showed being all about .010" over the SAAMI guage they included with the die. I'm trying to only size my brass enough to minimize case head seperation, and try to at least reach the hailed "four firing limit".

If they show .010” over, your chamber is likely a bit too deep. Size them back to .007” over, and see what your case life is.

 

[msinc]

Trying to achieve a .003" shoulder bump for these two rifles, I fired a few rounds in each with the gas system off (M1a) and gas plug remover (M1), hoping that this would give a more accurate depiction of actual chamber size. Would setting up my sizer to bump these Cases' shoulders back .003" be a good idea? I'm trying to avoid disassembling the rifles, and checking with a stripped bolt, because they're both bedded. As always, thanks guys!

In my experience with both of these rifles no. They both have a violent action, are hard on brass and they tend to stretch brass quite a bit. Simply firing the ammo and arbitrarily saying "I'll just bump them back .003" will probably not be enough. I have seen M1 Garands with minimum headspace still stretch good annealed ammo as much as .008". I guess with the gas system turned off they wont stretch, so give it a try.
Really the only proper solution to your question is to have the chamber headspace measured so you know exactly what you have for a starting point and size accordingly. I get that you don't want to tear it down.
I generally don't care for adjustable gas systems, most guys think they are necessary on anything as long as they are available. But the Garand can definitely be a rifle that benefits from one for certain. I would suggest doing the National Match gas plug hole alteration to the M1A.
As to how much to bump it back....how many rounds are you going to run thru it before you get a chance to clean it??? I never fired more than 40-50 rounds out of any of the ones I had and I always set the chamber headspace to minimum {close on a go gauge but feel the take up}. If you were going to war you might want it on the mid range {+.002"}. I always chambered my M1A with a JGS pull thru M852 match reamer and that worked out at minimum too. I would bump my ammo back .002" from minimum and once I loaded several right on zero, just to see if it was worth it accuracy wise. Didn't really seem to make a lot of difference, but I had no problems at all.
I have been reloading since 1980 and have yet to buy or use a small base die for anything. Not saying don't or that they are not necessary, but a small base die has so far not been necessary to me.
This contradicts other posts and I will not argue, do as you wish. Just my experience of what has worked for me. I don't see checking your chamber so you know exactly what you have as being arguable. Got my first M1A in 1985, first Garand a few years later and have barreled probably 30 others. Best of luck sir.

 

[fatelvis]

They both have a violent action, are hard on brass and they tend to stretch brass quite a bit. Simply firing the ammo and arbitrarily saying "I'll just bump them back .003" will probably not be enough. I have seen M1 Garands with minimum headspace still stretch good annealed ammo as much as .008".

This is what prompted my thinking that eliminating the auto-extraction, and having to be manually extracted/ejected, may give a more accurate picture of the rifle's chamber.

 

[cw308]

The Redding Competition shellholder set of 5 works well for me , start with the lowest deck height and work up with full contact with the shellholder and full length sizing die.

 

[rammac]

I've been using/reloading for/ and tinkering (I'm not a gunsmith) on these rifles since the mid 1970's so I've done a lot of things wrong over the years but I agree that the only way to tell what the headspace should be is to buy a set of headspace gauges. It should be done with a stripped bolt but with a little trial and error you should be able to find the true headspace dimension. I use a standard go and no-go combination of gauges but to be more accurate you might want to look in to buying a larger set of gauges, at least 5 to ensure that you're as close to the true dimension as you can be.

 

[Skeet69]

Unless something in that rifle/barrel/chamber is really hinky, FL sizing is all you should need. Even commercial and match brass should last in a properly set up M1 or 14. I've gotten 8-10 loadings on the much-maligned Federal brass on all of my match rifles.
Mike B

 

[Uncle Ed]

Take a new unfired case or a full length resized case and measure from the base to the case mouth and write it down.

Now take a fired spent primer and start it into the primer pocket with just your fingers. You might need to tap it on your reloading bench to keep it from falling out.

Now chamber this case and let the bolt face seat the primer and then extract.

Now you have two choices for measuring the case.

1. Measure the case from the base of the primer to the case mouth and write it down. Now subtract the first case measurement from the second and this will be your head clearance or the air space between the base of the case and the bolt face. You want .003 to .006 primer protrusion and difference between the two measurments for your M1A.

2. Measure the case from the base of the primer to the case shoulder with a Hornady cartridge case headspace gauge. This will be your actual chamber headspace and then set the die for .003 shoulder bump. Take a average of several primer seatings to get a uniform length.

You now know how to make the cheap bastards headspace gauge and set up your dies for the proper shoulder bump.

 

[cw308]

Uncle Ed
I like that , I always went with the stripped bolt method but that's a pretty simple test . Leared something new to try . I found the RCBS PRECISION MIC worked the best for headspace and ogive settings .

Chris

 

[Dusty Stevens]

Wilson case gage and the rcbs black box small base dies work well

 

[CarlGeorge]

I *just* began loading for the Garand. I did basically what @Doug Beach did: I took some fired brass and set up my die to bump the shortest ones back I believe .004-5". I used a regular FL die - not a SB die.

All of the brass sized this way chambered just fine.

 

[akajun]

I started out shouting service rifle with a m14 years ago, still sometimes break it out and still shoot my garands in vintage matches.
First things first, brass is important. There is a reason service rifle shooters go crazy o e LC, lc match, any usgi brass, and even federal, it’s thicker.
Next, no sb dies unless you have a problematic gun that needs it.
Set your die to just bump the shoulder back .004-5 and your good to go. Anneal every other firing and you could get 4-6 loading per case.
FYI, I never shot anything but usgi, lc match, or handloads using 4895 and 4064 , other powders May affect dwell time and be unlocking the action while it’s syill got the brass expanded. Maybe that’s your issue

 

[NorCalMikie]

Full length resize and be done with it. If you're getting "case head separation", you've moved the shoulder back too far more than once.
Be sure to double check the OAL of your resized brass. Once a long case gets chambered, you may not have a big enough hammer to get the bolt open again. (speaking from experience) And make damn sure you keep a "broken case extractor" in your range bag. (and a good dead blow hammer) Don't go shooting without one of each.
As far as resizing, set your dies so you push the shoulders back to where YOU want them. If it chambers in your M1A, shoot it and be ready to shoot again, X 20. Maybe 5000 down the pipe with no issues, other than a sore shoulder.

 

[msinc]

.......I took some fired brass and set up my die to bump the shortest ones back I believe .004-5".........
All of the brass sized this way chambered just fine.

Not judging your method, I could care less. If it works then it works and I am by no means suggesting you change anything.....but the fact is you could bump them back .010" and they would also go right in the chamber. Going right in the chamber, feeding and bolt closing doesn't really mean much. "chamber just fine" is different than go in the chamber and fit properly to be safe. This is the whole point to knowing exactly what the chamber length vs. sized case length is, which is the headspace of a given cartridge in a specific rifle.
One thing that sometimes confuses reloaders about military rifles...the Army had "Go", No-go", "Field" and "Field Reject" headspace gauges. The field gauges were intended to be used only in the field where a barrel and/or bolt couldn't be changed. The rifle will fire a round and the Army considered them safe right up to feeling take up on the reject gauge.....the difference is that unlike us, the Army is always firing new brass and not picking it up to load again.

 

[Uncle Ed]

The one thing to remember about measuring a fired case from a M14/M1A is the case can stretch longer than the chamber. And this depends on the powder burn rate and the type case used. This is why I posted the primer method for chamber length if you can't shut off the gas pressure and possibly measure stretched cases.

If you look at the SAAMI cartridge and chamber drawing below for the .308, headspace is listed as min and max with .010 in between. And GO and NO-GO gauges are used for setting up new or re-barreled rifles. And a Field gauge is approximately .007 longer than NO-GO gauge. Meaning after initial headspace adjustment you have .007 to .009 allowable increase in headspace due to wear.

G l e n D . Z e d i k e r

The distance between the military 7.62 GO gauge and Field Reject is .010, and the Field Gauge is .001 shorter than the Field Reject gauge. Meaning if the bolt closes on a Field Reject gauge it has gone beyond .010 maximum headspace. Read below for the Pacific "Field" headspace gauge, it is just under the .010 max headspace limits.


Pacific Tool and Gauge offers three lengths of headspace gauges per rifle caliber. In order from the shortest to longest, they are: GO, NO-GO, and FIELD:

1. GO: Corresponds to the minimum chamber dimensions. If a rifle closes on a GO gauge, the chamber will accept ammunition that is made to SAAMI’s maximum specifications. The GO gauge is essential for checking a newly-reamed chamber in order to ensure a tight, accurate and safe chamber that will accept SAAMI maximum ammo. Although the GO gauge is necessary for a gunsmith or armorer, it usually has fewer applications for the collector or surplus firearms purchaser.
   
   
2. NO-GO: Corresponds to the maximum headspace Forster recommends for gunsmiths chambering new, bolt action rifles. This is NOT a SAAMI-maximum measurement. If a rifle closes on a NO-GO gauge, it may still be within SAAMI specifications or it may have excessive headspace. To determine if there is excessive headspace, the chamber should then be checked with a FIELD gauge. The NO-GO gauge is a valuable tool for checking a newly-reamed chamber in order to ensure a tight and accurate chamber.
   
   
3. FIELD: Corresponds to the longest safe headspace. If a rifle closes on a FIELD gauge, its chamber is dangerously close to, or longer than, SAAMI’s specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been inspected and repaired by a competent gunsmith. FIELD gauges are slightly shorter than the SAAMI maximum in order to give a small safety margin.

RELOADING FOR THE MATCH M14
Glen D. Zediker

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=17&ved=2ahUKEwitybqT1s3fAhUJzlkKHWP3C9EQFjAQegQIChAC&url=http://www.zediker.com/downloads/14_loading.pdf&usg=AOvVaw0tVzg215hdzh0mGPudTRx0