This past Saturday I headed out to the range with some ROK made Q3131A1 (headstamp: WCC '09) and some US made Q3131 (headstamp: Nato cross, WCC '08). The rifle used was a RRA A4 with a 20" chrome lined, Wylde chambered, 9 twist barrel. It was fired from a bipod with sand bags used to rest the stock on. I only fired 2 five shot groups of each type as I had very little ammo to work with, the range was 100 yards. Don't have a camera so sorry about lack of pics.

1 Q3131A1 (Lot #PSD09B102-049 / 09.02.07.16:42)....
*Chrony results as measured 15' from muzzle ranged from a low of 3279 to a high of 3334 with an average for 10 shots of 3316.
*First 5 shot group measured 2.1", the second group measured 2.375"
*A few pieces of the brass had offcenter flasholes (similar to the Guat brass I have)
*No FTF's or FTE's with this ammunition although on both occasions it failed to lock the bolt back (I only loaded 5 rounds at a time in the mag)
*For the reloaders who are interested in this brass, I measured the case head thickness of each round and they ranged from .184" - .191"


2 Q3131 (Lot #BL32)....
*Chrony results ranged from a low of 3302 to a high of 3357 with an average for 10 shots of 3332
*First 5 shot group measured 3.04", the second group measured 1.4"
*I had 4 FTF's with this ammo (it reminded me of how Radway Green acted), it also failed to lock the bolt back on both occasions
*Case head thickness measurements on this brass ranged from .188" - .194"

I have not had any cycling issues with my handloads or Guatemalan surplus that I have fired through this rifle.

Wylde chamber, also forgot to add that it's a factory built gun. Also, found it interesting that among the box of Q3131 I found one commercially headstamped round but the primer was crimped that same as the rest of the ammo.

Interesting. The muzzle velocity for your 10-shot string of Q3131A1 would be 3338 FPS (which is well above the mil-spec for genuine M193.) I recently chronographed a lot of Q3131A1 that was produced just two days before your lot. From a relatively new 20" Colt barrel with a NATO chamber, the muzzle velocity was only 3180 FPS (which is below the mil-spec for M193.) The same barrel produced a muzzle velocity of 2800 FPS for MK262 during the same chronograph session and a muzzle velocity of 3279 FPS for XM193, also during the same session.

Your Wylde chamber seems to be producing significantly higher velocities, which would indicate higher chamber pressures as well. Have you chronographed any loads with that same barrel back-to-back with a barrel that has a NATO chamber?

That would be the comparison to make, same length for both barrels. Tell your brother he needs to loan you his rifle "for the sake of science."

Excellent work, VenomousDuck! According to your data, between the Q3131A1 and Q3131, the Wylde chambered barrel shows an average increase in velocity of 100 fps over the NATO chambered barrel . To quote Ken Oehler, "You need pressure to get velocity," which means the Wylde chamber must also be increasing pressures over that of the NATO chamber.

I have yet to see anyone produce credible data to support that statement. With the comparisons that I have seen, people try to compare the velocities of a stainless steel barrel to that of a chrome lined barrel with a NATO chamber. However, most stainless steel barrels for AR-15s do not have a NATO chamber; therefore differences in velocity are for more dependent upon the differences in the chamber than the metal.

Anyone ever see any difference in accuracy between Q3131A ( Israeli?) an Q3131? It has been awhile, but it seems the Q3131A has been more accurate?