RELOADERS CORNER: 5 Simple Steps To M1A Reloading Success

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The M14/M1A can be a cantankerous beast to reload for, so follow these suggestions to tame it down. Keep reading…

M14 match shooter

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.

Lake City Match ammo
Back in the day… Here’s what you got, which was the same as what everyone else got, for a DCM (now CMP Inc.) rifle tournament. “Here ya go son, and good luck…” and since we took as much luck out of the equation as possible, we all used a rifle chamber in our M14s and M1As that maximized Lake City Match ammo performance. And that’s why I’m writing all this…

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.

Headspace reading Lake City Match
The true M14/M1A match chamber is a short chamber: headspace is very tight. That’s because Lake City Match ammo is short. Compare this to what you might want to use, and if you have a genuine match chamber, best make sure the ammo fits… Measure both the results of sizing operations and also any new ammo or brass before you fire it in one of these chambers! I have encountered commercial .308 Win. rounds that were too long out of the box (cartridge case headspace dimensions). Here’s a cartridge headspace read on a Lake City Match compared to a commercial Winchester match load (inset) I had on hand. Read taken with a zeroed Hornady LNL gage. And NEVER fire commercial ammo intended for hunting use; the component mix and round structure is almost certain to be wrong.

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.

M14 gas system
These rifles have an overactive gas system that tends to create premature bolt unlocking, and this leads to excessive case expansion. I recommend resetting the fired case headspace to match a new case reading for safety’s sake.

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.

Forster National Match dies
A Forster “National Match” die set is a guaranteed way to ensure adequate sizing for an M1A match chamber. This sizing die has additional shoulder “crunch” built in, and that’s the “National Match” part: it essentially replicates Lake City Match ammo dimensions.

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.

308 components
Here’s a full component set I recommend, and use, for true match chambered M1As.

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

 

M14 loading dos/donts

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7 thoughts on “RELOADERS CORNER: 5 Simple Steps To M1A Reloading Success”

  1. I want to thank you for the info concerning for M1A. I had two of these through the years sold both of them just because of what you addressed in your artical. I wish I had been able to read your artical before I bought my first one. I’m sure I would still be shooting it instead of selling it. Oh I did tell the person buying it my reason for selling it, it just didn’t like my reloads at all.

  2. I’m surprised to see no recommendation of the military H-test (page 4., MIL-P-46610E(MU)) sensitivity spec primers now available. CCI #34 is a magnum primer made to that spec, which makes it great for cold weather loads, for older formula ball powders, or with partially-filled cases (e.g., most .30-06 Garand loads). But for .308 stick powder loads there is also the TulAmmo KVB762 primer which is standard power and produces some of the lowest SD’s I’ve ever seen. Whatever you think about the Russians politically, they do love their target shooting and know how to get consistent ignition in a properly seated primer.

    The only issue the KVB’s have is burrs on the cup edges like CCI had before their process revamp (1989). Those of us who had Dillon presses by that time will remember how hard older CCI primers were to seat flush on those machines, and how they worked fine after that time. So, be prepared to apply some extra seating force with KVBs and that you may need to resort to reaming or swage your primer pockets to maximum profile even if they have no crimp to begin with. The Forster Co-ax press’s built-in primer seater works best with these and provides a fixed depth ram at -0.005″ below flush with the head face which is perfect for floating firing pin gas guns, whatever primer you choose. I gave up on seating the KVB primers in hand tools, as I get hand cramps from the effort.

    For anyone trying to understand primers better, you might want to look in the Shooting Times online public archive for an Alan Jones article called Mysteries And Misconceptions Of The All-important Primer.

  3. Re: M1A Reloading
    You say “Nothing faster than H4895”. Respectfully, it should be nothing slower. Please, allow me to explain.

    A slower burning powder will have more residual pressure remaining at the gas port when the gas port is exposed by the passing bullet, because the slower burning powder’s peak pressure occurs further from the chamber (and closer to the gas port) than a faster burning powder’s peak pressure would, because a faster burning powder’s peak pressure occurs sooner after ignition than a slower burning powder’s peak pressure after ignition.

    Put another way: The sooner the peak gas pressure occurs in the bore, the more time the gas pressure has to decrease in the ever increasing bore volume the bullet is creating behind it while on it’s way to the gas port. The bullet’s travel down the bore is quickly increasing the bore’s volume (empty space) that the previously peaked pressure can expand into, thereby lowering the overall pressure.

    “Slower” burning powders create more pressure at the gas port, and should be used with caution in gas guns, especially direct impingement gas guns, and especially if those DI guns have large, ie: eroded, gas ports.

    1. That was a total mess up on my part and thanks for seeing it. Yes. Nothing SLOWER. I will correct the text. Too big a hurry sometimes…

  4. One other point to note: I see Glen has a short number on the digital caliper using the Hornady (nee Stoney Point) case comparator. Those comparators are good tools, but you have to be aware the hole in the aluminum comparator head has to have a slight radius at its edge to avoid cutting cases or dulling the hole and changing readings over time. As a result of that radius, they normally read a few thousandths below the actual value. How much too low varies with the individual insert, but -0.003″ to -0.008″ is the range I’ve seen reported by others. My own 0.400″ insert reads -0.004″. I’m fortunate to have other measuring instruments for my machine tools to confirm this with.

    If you want an valid actual value, the easiest way is to first zero the comparator on a known accurate good quality headspace gauge, and then measure your case and add or subtract the difference you get to the gauge’s value. If it is the same headspace gauge that matches your chamber headspace, then you know exactly how much shorter than your chamber a resized case measured on the comparator is. Alternately, you can zero the comparator against the caliper jaw, measure the headspace gauge and see how much the reading is below the gauge number, and then add that much to all your future readings.

  5. Kin you splain me this? If the firing pin is still complete with the tailpiece attached, how does it get past the receiver bridge while the bolt is in an unlocked condition to cause the much publicised “slam fire”? Just askin.

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