Sorry to beat a dead horse but.... I have been dealing with a ftex since I bought my 14.5 LMT W/CMT bolt. I've read all I could find and went though the fixes (#60 o-ring, heavier buffer and yesterday a wolff extractor spring.)and it is not short stroking. I've used WWB but mostly Rem UMC 55 gr with multiple mags. Yesterday after about 60 rds of the UMC (the last I had of it) I had about 6 ftex, some with spent cartrige on top with live round wedged underneath and some with spent still in chamber. All I had left was wolf 55gr I had never run through it. After about 200 rounds including including 3 consecutive quick mag dumps not one single fte. Was it the UMC or did it self polish after about 250 rounds of UMC and some WWB?

Certain guns don't like certain ammo. I have yet to see a good explination why, it just is the case. That's why all the gun rags test their firearms with at least 4 or 5 different brands of ammunition since two bullets out of the same box may result in one gun shooting well and another poorly, or vice versa. If it runs with WWB, shoot WWB and not UMC.

new rifles always get quality hot ammo with me for the first 500-1000 rnds to break in the chamber. i also give my chamber special attention when cleaning ( i use a 9mm brush) to avoid this problem. after that, i shoot whatever's on sale. YMMV.

Cases left in the chamber is an Extractor tension problem.

Double feeding (two live rounds) is a mag problem.

Since it is safe to say that Wolf has more surface tension (poly coating), the chamber seems fine, but when you go to hotter ammo, you could be back in the same old boat with mag problems (buffer impact off the back of the receiver extension), and ejection problems is the rifle is over cycling (causing the case to be chamber bound more during unlock).

Hottest ammo out (in spec) is M-193, so if the rifle will run with it, it's Golden (but may still be ammo sensitive in regards to what will run/will group the best).

Thanks for the info guys.

Quoted: new rifles always get quality hot ammo with me for the first 500-1000 rnds to break in the chamber.

What exactly happens when a chamber is broken in???  A chrome lined chamber doesn't "break in"!  It erodes in the throat over time.

Harkonan, Your rifle should work FINE with UMC ammo.  It's not very hot ammo, and I would be concerned if any of my guns wouldn't digest it.  Have your weapon checked out.

Quoted: Quoted: new rifles always get quality hot ammo with me for the first 500-1000 rnds to break in the chamber. What exactly happens when a chamber is broken in???  A chrome lined chamber doesn't "break in"!  It erodes in the throat over time. Harkonan, Your rifle should work FINE with UMC ammo.  It's not very hot ammo, and I would be concerned if any of my guns wouldn't digest it.  Have your weapon checked out.

The term break-in means to self polish out threw live fire.  And yes, even a chrome plated chamber will polish out threw live fire given enought rounds.  It's when there are milling flaws/grooves that are produced in the chamber, then plated over that breaking-in will not resolve.

There have been reports of tight chambers on some LMT barrels. Not saying that this is the case here, but something to ponder.

BTW a good functioning rifle does not need a "break in period" of 500-1000 rounds,

Quoted: BTW a good functioning rifle does not need a "break in period" of 500-1000 rounds,

Totally agree since it will have Colt or FN stamped on it, and will produce groups at or under 3 MOA.

Now on the other hand, if you want to run a tight ass match chamber in an auto loader, don't even try to group it in the same class as a true battle proven design spec'd rifle.

Huh? If it has Colt stamped on it, it's probably a pretty good barrel. 4150 steel, MP tested, 5.56 chamber, the works. If it has FN stamped on it, you're probably looking at an old military barrel or a factory reject, in which case the chamber problem might just be the tip of the iceberg.

Anyway, if your problem fixed itself, more power to you. It might have been a burr on the chamber or your chamber and ammo were both on the high side of tolerances. Shoot a few hundred more rounds and report back if you have any further problems.

Quoted: Quoted: new rifles always get quality hot ammo with me for the first 500-1000 rnds to break in the chamber. What exactly happens when a chamber is broken in???  A chrome lined chamber doesn't "break in"!  It erodes in the throat over time. Harkonan, Your rifle should work FINE with UMC ammo.  It's not very hot ammo, and I would be concerned if any of my guns wouldn't digest it.  Have your weapon checked out.

perhaps this philosophy works for you demigod, but my rifle is not a range queen. i carry it on duty, which has different, higher expectations for performance. as dano explained, this process polishes the chamber, usually removing any burrs or imperfections unless they were there before the chrome plating. i build these rifles for others on my department and i've noticed a disturbing trend with major companies making the chambers too tight (bushmaster comes to mind). if a barrel isn't clearly reliable after 500-1K of XM193 or other quality ammo, it gets trashed. you should do your homework, demigod, before you call 'BS' on anyone.