i’ve actually tried to induce this failure on multiple guns, and never been able to get a case to stick… being a bit tighter than 556, i tried on a wylde chamber not too long ago- fired about 400-500 rounds of wolf, then popped some good ol’ low pressure brass PMC in there… perfect extraction for another 300 rounds.
obviously the law of inevitability dictates that it will happen to totally in-spec chambers from time to time, but i still think even this is probably at least partially a chamber issue most times.
That’s true, but you usually don’t choose 5.56x45 chambers for absolute accuracy. Reliability is much more important. If accuracy is your goal, then stick with the .223 standard or Wylde chambers and .223 ammo.
5.56 chambers are still more than adequate for combat accuracy and many are still more accurate than the shooters who pull the trigger.
that does actually sounds vaguely familiar- it might have been just a short-lived temporary problem that was immediately addressed. everyone’s had a bad run at some point.
I have personally seen Ned’s reamer remove metal from an LMT chamber, and according to Dean Caputo, he has seen it happen frequently with LMTs (data from approx 2 years ago). Now that is not necessarily bad, as the amount of material removed was far less than the other “5.56” guns I saw being reamed, and if you reamed a Noveske you would also see a removal of material.
In my personal experience with 2 LMTs, the LMT chamber is not to be worried about unless you are seeing pressure issues.
I could be wrong here, but didn’t Ned write an article in SWAT in which he tested a gun or two for precision, then reamed the chambers, and retested, and saw virtually no difference? I could be mistaken, but it appears to me that the supposed “inaccuracy” of the 5.56 chamber is more linked to the types of 5.56 ammo and barrel quality than chamber issues to anyone except for the yellow-glasses crowd.
I did just that and found no statistically significant dif. That my sound like I’m obfuscating the results-- I’m not-- it’s just that some loads shot a little better and some shot a little worse-- and all those differences were within normal variances. What I mean is, if any of us shoots 10, 10-shot groups, they aren’t all going to be the same. There will be some little variances caused by conditions and our concentration.
One thing that kinda surprised me was that XM193 appeared to for-sure benefit from the reaming. Every post-reaming group was smaller than every pre-reaming group.
Some of you may have caught my little follow-up letter to the Editor at SWAT Magazine, about a friend of mine who had a batch of uppers his department had shelved due to chronic popped primers. They replaced the uppers and lost the problem. He got them out one day and gaged throat depths (they varied a fair amount), grouped them (10 of them as I recall), and chrono’d them. All 16" guns and grouping was only at 25 yards, but no dif in group sizes. However, he lost 150-ish FPS by reaming! In the case of one upper it was just under 200 FPS… this happened to be the one with the shortest throat, and it also happens to have popped a primer in his pre-reaming shooting. The velocity of the shot that popped the primer?
3400 FPS. That was with XM 193.
I think that really exemplifies the “don’t shoot 5.56 NATO ammo in a .223 chamber” suggestion. And definitely a case where you’d actually breathe a sigh of relief for losing 200FPS!
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