Tag Archives: NATO

RELOADERS CORNER: 5.56 NATO: “GO,” “NO-GO”

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This “warning” has been around, and around, for years, but it’s still not always heeded, or understood. Read why and how it matters HERE.

nato stamp
The circle-cross stamp is a NATO-spec cartridge. Your barrel might be marked “5.56” or a more lengthy disclosure referencing its specs. If it’s “.223 Rem.” do not fire a NATO round through it! Your barrel might also not be marked at all. I’ve increasingly seen that. Get it checked. A NATO round will chamber perfectly in a .223 Rem. All exterior dimensions are patently the same, again, it’s the pressure level.

Glen Zediker

I know this is “Reloaders Corner,” but, every now and again at least, I rip open the end of a cardboard factory cartridge box, or five.

I just got finished building up a “retro” AR15 for a new book. Reasons for that are a few, but probably the main one was that I wanted to recollect the one that “got away,” well, the one that I let go. Errant short-sighted judgment, as is common in youthful people. So I built a replica M16A1, circa mid-60s, well, of course, with only two selector stops. At the heart of that rifle is an original-spec barrel, chrome-lined, NATO chamber.

5.56 stamp
This is a NATO chamber stamp. If it’s “.223 Rem.” that’s NOT the same!

That’s leading to this: I opened up a few boxes of “genuine” NATO 5.56 to check it out with, something I honestly haven’t fired for years and years. Dang. That stuff is potent. Over the past several years, the pressure level has increased. Current standard is a little over 62,000 PSI. (NATO is technically measured differently than commercial, but the figures I give here are accurate for comparison.) Compared to SAAMI specs for .223 Remington (commercial) that’s a solid 7,000 difference. (That SAAMI-spec figure has likewise increased over the years, judging from recent test figures I’ve seen respecting commercial .223 Rem.; most references heretofore were max at 52,000 PSI.)

The main impetus for this article, though, came from a recent experience at a local gun shop. I went in search of a sub-sonic .300 Blackout load, and they had one in .300 Whisper. The counter person told me that it was “exactly the same as .300 Blackout, just like .223 is the same as 5.56…” Whoa. Neither statement is true, although Whisper specs are plenty close enough to Blackout that no differences factor in safety or function. However! I didn’t take the time to lecture, but, dang, .223 Rem. and 5.56 NATO are not nearly the same.

First point: do not fire NATO-spec ammo in a rifle with a chamber marked “.223 Remington.” It will, not may, be over-pressure. Reasons have to do with chamber specifications for 5.56x45mm NATO and those for SAAMI-spec .223 Remington. There is a significant difference in the leade or “freebore” cut comparing SAAMI to NATO. That’s the space in a chamber ahead of the cartridge case neck area that leads into the rifling. NATO is radically more generous, meaning “bigger”: longer, more volume. (About 0.150 inches, based on my measurements of bullet seating depths that touch the lands.) There is relatively much more room for expanding gases to occupy in a NATO chamber. In a SAAMI chamber there’s much less room for expanding gases to occupy. The additional pressure is about the equivalent of another full grain (or more) of propellant in the case. Yikes.

high pressure nato
Here’s what happens putting a factory-fresh NATO round through a .223 Rem. chamber. This case is clearly beat. Sure, it might, should, hold up for that firing, but the case is done and the gun took a needless hammering.

nato beat case

There are other little nit differences to pick between the SAAMI and NATO cartridge, and, therefore, chambering specs, but they don’t really factor in a material sense. There’s bound also to be just as many small differences in cartridge dimensions from one maker to the next. I’ve measured enough to tell you that’s true.

Now. What this has to do with reloading (finally, I know) is based on a question I’ve gotten over the years, a concern to some, or at least, as said, a question. And the answer is that you’re better off going with .223 Remington loading data for any ammo intended for “general” range use. That means blasting away on an afternoon. Just because it’s a NATO chamber does in no way mean you’re supposed to run NATO-spec ammo through it! Back it off and enjoy it more.

If you’re relying on a factory-published data manual to give a place to start, or stop (something from Sierra, Hornady, Lyman, or so on) pay very close attention to the test barrel specifications. Clearly, barrel length has a big influence on attaining the published velocities, and some load combinations are going to be worked up using considerably longer barrels than what the most of us have on our AR15s. But the biggest factor is the chamber used in the test barrel. If it’s a SAAMI-spec (sometimes called a “SAAMI-minimum”) chamber then the data should be on the conservative side. Should be. Do not, however, bank on any idea that you should jump straight to the maximum load listed if you’re loading for use in a NATO. There are, always, too many factors that otherwise create more or less pressure (primers, cases, propellant lot, and more).

As time goes by it probably is less likely to encounter a semi-automatic “.223” that’s not a NATO, but it will be marked as such! Clearly, most ammo is used in the most popular guns. That’s not going to be a bolt-action anymore. Make no mistake, though, AR15s exist plentifully that have SAAMI chambers, and I see a lot of aftermarket barrels that are cut with that minimum-dimension reamer.

ANOTHER OPTION
So what’s a “Wylde” chamber? This is a chambering spec developed by Bill Wylde, one of the early and leading pioneers in the quest for improved AR15 accuracy. It is popular and available, especially in aftermarket barrels. What it is, is a chamber that’s in-between SAAMI-minimum and NATO, leaning closer to NATO. Rumors are true: it’s safe to fire NATO-spec factory loads through a Wylde. The Wylde was designed upon the introduction of the heavier competition bullets with the idea of providing more freebore to accommodate the necessarily longer cartridge overall lengths necessary with something like an 80gr. Sierra, but keep the amount of jump to a minimum with shorter bullets fed from the magazine.

This article is adapted from Glen’s books, Handloading For Competition and Top-Grade Ammo, available at Midsouth HERE. For more information about other books by Glen, visit ZedikerPublishing.com

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

Reloaders Corner: AR15 Chamber Options

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It’s vital to understand “which” chamber is in your AR15. What you don’t know can create big problems. Here’s why.


Glen Zediker


I’ve talked over or at least touched upon this topic, here and there, in other articles. And this week I got four phone calls asking for advice on “which” AR15 chamber I’d recommend. I guess that sort of spurred creation of this article. My primary goal (always) is to answer questions, and ideally before they are asked. So…

NATO mark
A TRUE NATO load always has this mark on its base: the cross-in-a-circle stamp. Some commercial ammo that appears to be mil-spec may or may not be, but err on the safe side.

There are a few options today, and, no, it never was “simple.” There have always been two distinct chambers cut for .223 Remington and 5.56x45mm NATO. And that’s the difference right there! See, .223 Rem. is a commercial round, 5.56 is a mil-spec round. Yes. They are “the same,” but they’re not. The difference is in how these two are loaded with respect to pressures. NATO is a whopping lot hotter. To the tune of +15,000 PSI.

The differences in the chambers are, pretty much, that a NATO has a significantly longer throat or leade or freebore, whichever term is preferred. This is the area in a chamber that extends beyond the case neck cut.

Chamber-All gage
I use a Hornady LNL OAL gage to find out exactly the length of the chamber throat. Get one at Midsouth. This read shows “NATO” by the way. Sierra 80gr MatchKing at 2.550 inches to touch the lands. Wylde should read 2.475. SAAMI-minimum will (usually) be 2.395.

This area in a chamber accepts the initial gas expansion, so, in one way, it can be looked at like an expansion chamber. More room for expanding gases effectively reduces stress on the case. When this area is lengthened, there’s more room, less pressure build. When this area is shortened, there’s less room, more pressure build.

As said, .223 Rem. is short, NATO is long. Take a NATO-spec round and fire it in a .223 Rem. chamber and there’s too much pressure. The .223 Rem. will “fit” just fine; there’s no influential differences otherwise in chambering specifications between .223 Rem. and 5.56.

You’ve probably heard all that before. It’s very important to know. “Which” chamber affects making loaded ammo choices, and also in interpreting reloading data.

NATO pressure
Here’s “real” NATO fired in a commercial .223 Rem. chamber. Ouch. The imprints and general beating the case head shows are the result of the additional pressure in the NATO loading, and the .223 Rem. chamber’s inability to excuse that much extra pressure.

Short history as to the reasons these two chambers exist: .223 Rem. in civilian, commercial application was a varminting-type round, along the lines of .222 Rem. When SAAMI (Sporting Ammunition and Arms Manufacurers Institute) laid down the specifications for that round it did so based around the prevalent short .224 bullets of the day, which were often 52-grain flatbase designs. For best accuracy with the little bullets, the throat was kept short, decreasing the distance the bullet had to travel to engage the lands or rifling. Some, most, me included, call this chamber a “SAMMI-minimum.” The mil-spec ammo assembled for M16s used a 55-grain boat-tail loaded to a higher velocity, and the longer throat was specified to handle the extra gas.

What matters is knowing that you don’t have a .223 Rem. chamber. A NATO can handle anything.

Most AR15s I’ve handled in the past good long while have NATO chambers. It’s the only thing that makes any sense for someone, anyone, who wants to fire sto-bot ammo. Not all the mil-type commercial loads (like the “white box” varieties) are true NATO spec, but if the ammo is not marked “.223 Rem.” it might be a tad amount to a lot hotter than a short-throated gun should handle. True NATO ammo has a distinct marking on the case base.

There is now another what’s become “standard” chamber for AR15s, and that’s the Wylde. Named for AR15 accuracy pioneer Bill Wylde, this reamer specs fall between SAAMI-minimum and NATO. Bill started cutting these chambers for NRA High Power Rifle contestants who needed more room in the throat to accept the long 80-grain bullets but not so much room that the shorter 69-grain bullets were having to leap a gorge to engage the lands. A compromise. A Wylde is a good chamber, and a good choice.

Compare .223 chambers
Here’s the best way to see what’s going on with AR15 chambers. These are Sierra 80-grain MatchKing bullets loaded to an overall cartridge length that has the bullet touching the rifling. Left to right: SAMMI-minimum .223 Rem.; Wylde; NATO. Wahoo. Big, big differences. There’s a little more than 0.150 inches between the SAAMI-minimum and the NATO and that space in the throat handles the extra PSI of NATO-spec loadings. It is also, by the way, how to know (or one way to know) the actual “length” of a chamber throat.

Here’s how it breaks down, according to me:
SAAMI-minimum or commercial .223 Rem. chamber is good for those who are wanting the best accuracy from light bullets. Can’t run mil-surplus ammo or NATO-spec commercial though.

NATO is for anyone who wants to shoot anything and everything out there safely.

NATO stamp
There’s a few ways I’ve seen “NATO” marked on barrels, and I’ve seen a good number of barrels that aren’t marked at all. That’s terribly irresponsible. Look for “5.56” since that seems to have become the more common way to denote “NATO.”

Wylde is more or less an “Improved NATO,” and my experience has been that it will safely handle true NATO loads, even if that’s not its intended design. I base that on spent case condition. It will shoot a little better than a NATO with lighter, shorter bullets. The Wylde is available more and more commonly now from different manufacturers and in “drop-in” accessory barrels.

winchester .223 ammo
If you have a “.223 Rem.” stamp on your barrel don’t feed it any ammo that is not clearly likewise marked “.223 Rem.” Should say the same on the case headstamp. If it doesn’t read “.223 Rem.” do not fire it in a barrel stamped “.223 Rem.” This ammo is safe for any AR15. If you don’t see a stamp on your barrel, find out…or just fire .223 Rem.

The preceding was adapted from Glen’s newest 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