The M14/M1A can be a cantankerous beast to reload for, so follow these suggestions to tame it down. Keep reading…
Glen Zediker
The “5 steps to success” are at the end of this article… First, read about why they will matter as much as they do!
A couple times back I decided that the best topic to write about might be the most current, and I defined that by the most recent questions I fielded on a topic. As the assumption goes: they can’t be the only ones with that question… So, over this weekend I had a series of questions from different people all on the topic of reloading for the M1A, the civilian version of the military M14.
Now. Since the M14 was the issue rifle of choice for a good number of years, and without a doubt the (previously at least) favored platform for the various-branch military shooting team efforts, it went through some serious modifications to best suit it to that very narrow-use objective: High Power Rifle competition. Although the M14 hadn’t been routinely issued to most troops for decades, it was still going strong in this venue. That changed in the mid-90s when Rules changes boosted the AR15 platform to prominence, and soon after, dominance.
Match conditioning an M14 involved modifications to virtually every system component, and resulted in a fine shooting rifle. Very fine. Amazingly fine. The one mod that prodded the impetus to write all this next was the barrel chambering specification changes. A while back I went on about what 7.62 NATO is compared to its fraternal twin .308 Winchester.
Match-spec M14 chambers are decidedly NOT NATO! They’re .308 Winchester, pretty much. I say “pretty much” because they’re on the minimum side, dimensionally, compared to SAAMI commercial guidelines for .308 Win. Lemmeesplain: the true “match” M14 chamber is short, in throat and in headspace. The reason is ammunition bound. I’ll explain that too: Lake City Match ammo was and is a universal competition cartridge. Military teams compete in, well, military team competitions. Some are open to civilians, some are not. All, however, used issued ammo across the board. You were given your boxes of Lake City Match, or Special Ball, or one of a couple other same-spec variants, prior to the show and that’s what you used for the event. Everyone used the same ammo. Civilian or Service. There were exceptions, like long-range specialty events, but what was said held true the vast majority of the time. That meant that everyone wanted the same well-proven chamber, civilians too.
Given this, that’s why a “match” M1A chamber is different than a SAAMI. It was built to maximize Lake City Match accuracy. That’s a short round. The headspace is a few thousandths under what’s common on a chamber based around commercial .308 brass. 1.630-inch cartridge headspace height is regarded as minimum for commercial.
Check out headspace gages at Midsouth HERE
So sizing a case to fit a match M1A, especially if it’s a hard-skinned mil-spec case, takes some crunch. To compound difficulty, M1As and M14s unlock very (very) quickly during firing. The bolt is trying to unlock when the case is still expanded against the chamber walls. The little bit of space this creates results in a “false” headspace gage reading on the spent case. It’s going to measure a little longer than the chamber is actually cut. That can lead someone to do the usual math (comparing new case and spent case headspace reads) and end up with a “size-to” figure that’s too tall, that has the shoulder too high. For instance, let’s say the spent case measured 1.634 and the new case measured 1.627, indicating 0.006 expansion or growth. Given the usual advice (from me at least) to reduce fired case shoulder height by 0.004 (semi-autos) for safe and reliable reuse would net a size-to dimension of 1.630. But. There can easily be a “missed” 0.002-0.003 inches resultant from the additional expansion explained earlier. My advice for a match-chambered M1A is to reduce the fired case all the way back down to the new case dimension. That might sound like a lot, and it might sound excessive, and it might be — but, it’s the proven way to keep this gun running surely and safely. That, however, is not always an easy chore. Some mil-spec brass is reluctant to cooperate. And, by the way, don’t kid yourself about reducing case life. This gun eats brass; I put just three loads through a case before canning it.
Two helps: one is to use petroleum-based case lube, like Forster Case Lube or Redding/Imperial Sizing Wax. And size each case twice! That’s right: run each one fully into the die twice. Double-sizing sure seems to result in more correct and more consistent after-sizing headspace readings.
A “small-base” sizing die (reduced case head diameter) is not necessary to refit match brass into a match chamber. It might help using brass that was first-fired in a chamber with more generous diameter, but sized diameter isn’t really the “small” part of the M1A match chamber. Again, the small part is the headspace.
Take a look at these dies HERE
So that’s the source the problem reloading for this rifle. And, again, “this rifle” is an M1A with a true mil-match armorer’s spec chamber. We best make sure that our sized cases are going to fit the chamber, plus a couple thousandths clearance for function and safety. And safety mostly. M1As are notorious for “slam-fires” which happen when the free-floating firing pin taps the primer on a chambering round delivering sufficient intrusion to detonate. Impressive explosions result. If the case shoulder is stopping against the chamber before the bolt can lock over, that can be all the pin needs to maximize the effect of its inertia.
Speaking of, there are three sources and fortunately the same number of cures for slam-fires. One, first, is the correct sizing on setting back the case shoulder so the shoulder doesn’t stop against its receptacle in the chamber. Next is making sure there are no “high” primers; each primer should be seated at least 0.005 inches under flush with the case head. Next, and very important: primer composition, which equates to primer brand. Do not use a “sensitive” primer, one with a thinner, softer skin. Although they are great performers, Federal 205 are too sensitive for this rifle. Better are WW, CCI 200.
My thoughts
I don’t like this chamber… I also used one because I competed in events with issued ammo. I don’t recommend a “true” M14 chamber because that’s a NATO. Plain old standard .308 Win. specs work better and allow more flexibility in ammo and component selection. Even though the true mil-spec match chambers are not common, the reason I’ve written as much as I have on this topic over the years is because a mistake can be disastrous. One of the folks who wrote me one question shared a story about a friend who blew up his match M1A firing improper commercially-loaded ammo through it. Whoa.
A CASE FOR THE M1A
This gun needs a stout case. They won’t last long no matter what but they might not last at all if they’re too soft. I’ve broken some new commercial cases on one firing. Thicker/thinner isn’t the issue: it’s the hardness of the alloy. Harder material better resists reaction to the additional stress of premature system operation. New-condition mil-spec cases are great, if you can get them. Next best is Lake City Match that was fired in a match-chambered rifle. Stay completely away from anything, and everything, fired through a NATO-spec chamber. It’s nigh on not possible to size them enough to suit. For me, WW is the only commercial case I will run through my M1A. They’re thin, but pretty hard.
I did a whole chapter solely on reloading for the M14/M1A for my book Handloading for Competition that didn’t get printed into it for various reasons. However! I have the entire chapter available as a PDF download on my website. Get it HERE
And for even more info on reloading for the M1A, order the new book Top-Grade Ammo, available here at Midsouth. For more information on this book, and others, plus articles and information for download, visit ZedikerPublishing.com
