tkoglman
09-13-10, 18:29
My colleague has a 10.5" LMT. Over the past year, he's been having accuracy issues with it. At first we thought it was his optics, which EOTech refurbished for free. The accuracy problems persisted. At 50m the rifle would shoot 12-18" groups. Switching from M193 to 69gr. BTHP's cut the groups in half, but accuracy was still dismal. In comparison, my Sabre Defense barrelled shorty shoots close to 1moa.
I couldn't imagine that the barrel had been shot-out so quickly. I began to suspect that the muzzle crown was damaged, so I inspected the barrel closely. The crown was fine, but looking down the bore, from the muzzle, I could see a black ring around the bore about 3/4" down from the muzzle. I cleaned the barrel well and the black ring stood out even more. I've seen several bulged barrels in pistols, and this looked exactly the same - a black ring, a shadow, cast on the bore where the bulge is. I ran a swab down the bore and could feel it. The bulge is just ahead of the front of the FSB.
This must be the cause of the inaccuracy. The longer BTHP bullets were probably more tolerant of it than the 55gr FMJ's.
We sent an email to LMT, but I'm sure that their response will be that it is an ammunition induced problem - which it most likely is. I can't see it being a manufacturing problem. All he's ever put through the barrel (about 2000 rounds) is M193 and Federal LE ammo. He couldn't remember having a squib round at any point. The rifle had some cycling problems when he first got it - which were cured quickly with the right buffer - but after that its run perfectly. He also didn't remember ever having a bore obstruction. My guess is that the squib round occurred in the first 50 rounds as we were getting the right buffer in it, and we just didn't notice it.
Luckily for him, I have a spare Sabre Defense 11.5" barrel I can sell him. Has anyone ever had an experience with a bulged barrel in an AR before? I've never seen it before.
Thanks.
I couldn't imagine that the barrel had been shot-out so quickly. I began to suspect that the muzzle crown was damaged, so I inspected the barrel closely. The crown was fine, but looking down the bore, from the muzzle, I could see a black ring around the bore about 3/4" down from the muzzle. I cleaned the barrel well and the black ring stood out even more. I've seen several bulged barrels in pistols, and this looked exactly the same - a black ring, a shadow, cast on the bore where the bulge is. I ran a swab down the bore and could feel it. The bulge is just ahead of the front of the FSB.
This must be the cause of the inaccuracy. The longer BTHP bullets were probably more tolerant of it than the 55gr FMJ's.
We sent an email to LMT, but I'm sure that their response will be that it is an ammunition induced problem - which it most likely is. I can't see it being a manufacturing problem. All he's ever put through the barrel (about 2000 rounds) is M193 and Federal LE ammo. He couldn't remember having a squib round at any point. The rifle had some cycling problems when he first got it - which were cured quickly with the right buffer - but after that its run perfectly. He also didn't remember ever having a bore obstruction. My guess is that the squib round occurred in the first 50 rounds as we were getting the right buffer in it, and we just didn't notice it.
Luckily for him, I have a spare Sabre Defense 11.5" barrel I can sell him. Has anyone ever had an experience with a bulged barrel in an AR before? I've never seen it before.
Thanks.