So, wouldn't you know it.  As soon as I make a decision about what barrel to get, everyone is suddenly out of stock and has no idea when they will have more.  I'm looking to build an 18" medium contour mid ported SPR type setup.  No inventory + no projected date of availability = project has come to a screeching halt.  Trying to get back on track, I'm now considering a barrel chambered in Wyld. 

 

I plan on shooting mostly 5.56 NATO 62gr (green tips).  Is there any reason I should not go with a Wyld chamber?

I have a 223 Wylde Chambered AR that is set up for NM. From what little I know, there is just a minor difference in the chamber should angle / cut. Also, FWIW and YMMV, it is 'supposed' to be more for precision shooting. But who knows. I also have this chamber on an 18" HB Rock River AR15. For a carbine, that SOB was heavy as hell. The twist is going to provide the stability versus the chamber cut which only holds the case. Your land and grooves send that happy pill on its way.

P.O. Box 299 Geneseo Illinois, U.S.A. 61254 Tel 309-944-6939 fax 309-944-6949 [email protected]
April 4, 2011 Rev 1
TECHNICAL NOTE 74: 5.56 NATO vs SAAMI .223 REMINGTON
vs WYLDE CHAMBERS
BACKGROUND:
We are often asked about whether our rifles feature NATO (North Atlantic Treaty
Organization) or SAAMI (Small Arms and Ammunition Manufacturer’s Institute), or
Wylde chambers and whether it makes any difference.
FACTS:
.223 Remington (SAAMI standard) and 5.56mm (NATO standard) rifle chambers are
almost identical. The difference is largely limited to the “freebore”, the cylindrical space
in front of the casemouth, and the “lead” or “leade”, the tapered region that eases the
bullet into full engagement with the rifling. NATO and SAAMI cartridges can normally
be used interchangeably with no problem.
The SAAMI chamber incorporates less freebore and a tighter leade, which normally
provides better bullet-to-chamber fit and, therefore, better accuracy than the NATO
chamber. It is wonderfully suited to match bullets.
Millions of rounds of NATO ammunition have been fired safely in Eagle Arms and
ArmaLite’s® SAAMI chambers over the past 22 years. Occasionally a non-standard
round (of generally imported) ammunition will fit too tightly in the leade, and resistance
to early bullet movement can cause elevated chamber pressures. These pressures are
revealed by overly flattened primers or by powder stains around the primer that reveal
leaking gasses.
The first few rounds of ALL ammunition, from whatever source or lot, should be checked
for signs of pressure or any other defect before firing large quantities. If you have a
problem, you can generally bet that the ammunition meets neither SAAMI nor NATO
specifications.
ArmaLite® has adopted a practice of using a modified SAAMI chamber (Wylde) in its
stainless steel match barrels. This chamber is better for match use than the NATO
chamber, but fires the NATO ammunition perfectly. We use the NATO chamber in all
moly (phosphated) and chrome-lined barrels.
NOTE: ArmaLite’s® larger AR-10 series rifles are all chambered with 7.62 NATO
chambers. .308 Winchester (SAAMI standard) ammunition functions perfectly in the
7.62 NATO chambers.
© 2009 ArmaLite, Inc. All rights reserved. Reformatted 110404. THE WIZ

So, lemme see if I got this right.  The external dimensions of a 223 case and 5.56 NATO case are identical.  The NATO chamber offers more wiggle room than the 223 chamber and can withstand higher pressures.  For the 223 competition shooter, the slightly longer Wylde chamber allows 223 rounds to be tipped with heavier (and longer) bullets.  For the typical 5.56 NATO chamber shooter; the Wylde chamber is shorter, which improves accuracy since the bullet does not have to jump as far into the rifling.  The reduced headspace does not (in theory) affect reliability(cause jams) in a semi auto.  It's also my understanding that barrels chambered as Wylde are made from the same materials that 5.56 barrels are made from  and are just as strong.

 

Is that about right?

It is perfectly fine to shoot 5.56 out of a .223 Wylde barrel.

Wylde is the RRA version of 5.56/.223, other companies adopted it.

Wylde is VERY close to 5.56 Sam-r, which is a chamber cut that was from the marine shooting team. Both are safe for 5.56 ammo.

 

In reality, commercial chamber resents overlap all over the place. You can get .223 ones that are looser than some 5.56 NATO.

 

Wylde is a good compromise.