Tag Archives: SAAMI

Reloaders Corner: AR15 Chamber Options

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

NSSF, SAAMI Will Get Day in Court in Microstamping Suit

A California Appellate Court has reversed the Fresno Superior Court’s dismissal of the NSSF and SAAMI lawsuit seeking an injunction to block enforcement of the state’s ammunition microstamping law and remanded the case back to the lower court to hear arguments. Keep reading…


Source: NSSF Government Relations Update


microstamping
Microstamping uses laser-engraved codes on a firing pin with the idea of being able to trace a spent casing back to the gun that fired it. Results are inconclusive, and some say unreliable.

Gun manufacturers have the right to present evidence supporting their claim that technology does not exist to comply with a California law requiring new models of semi-automatic handguns to stamp identifying information on bullet casings, a state appeals court said Thursday [Dec. 1].

The ruling by the 5th District Court of Appeals in Fresno overturned a lower court ruling rejecting a lawsuit by two firearms trade associations [NSSF and SAAMI] that challenged the law. The appeals court sent the case back to the lower court for further consideration. “It would be illogical to uphold a requirement that is currently impossible to accomplish,” Justice Herbert Levy wrote for the appeals court.

Larry Keane, NSSF Senior Vice President and General Counsel: “We are pleased by today’s ruling because it means we will now be able to prove in court that this ill-considered law must be enjoined, because it is literally impossible to comply with its requirements, and the law never requires the impossible. We have long maintained that this nascent, unproven, and unreliable technology should not have been mandated.”

Supporters of the law signed by Gov. Arnold Schwarzenegger in 2007 touted it as a help to law enforcement in soliving gun crimes by allowing them to link bullet casings to specific guns. Hannah Shearer, a staff attorney at the San Francisco-based Law Center to Prevent Gun Violence, said that the argument that gun manufacturers can’t comply with the law is bogus and will be rejected by the trial court. “California’s microstamping law gives law enforcement a strong tool to investigate and solve gun crimes and also combat gun trafficking,” she said.

The law requires new handgun models to have a microscopic array of characters in two spots that identify the gun’s make, model, and serial number and that are transferred by imprinting on each cartridge case when the gun is fired.

State officials said gun manufacturers could comply with the law by putting two stamps on the firing pin. But the appeals court said the Legislature required dual microstamping to prevent criminals from defeating the process by defacing or removing the firing pin. Allowing two stamps on the firing pin would not serve that purpose, Justice Levy wrote.

Gun rights groups say it is not possible to microstamp two areas of a gun. Only the tip of the firing pin can be microstamped, and current technology doesn’t allow the stamp to reliably, consistently, and legibly imprint on the cartridge primer from that part of the gun, they claim.

The law was supposed to take effect in 2010 but was delayed because of patents on the technology, including at least one that had been bought up by a gun rights group to delay the law’s implementation.

The law doesn’t impact guns already on the state’s official firearm roster. Only new or modified semi-automatic handguns sold in California must be equipped with the technology. NSSF Senior Vice President Larry Keane said no new models of pistols have been introduced in California since the law took effect, and hundreds of pistols have been taken off the state’s firearm roster because even slight changes render the gun a new model. “When we ultimately prevail in this case, law-abiding consumers in California will once again be able to purchase new models of pistols this law currently prevents our industry members from selling in the state,” Keane said.

A separate lawsuit challenging the law on constitutional grounds is pending before a federal appeals court in San Francisco.


LINKS

Fast Facts on Microstamping .PDF