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2/19/2009 1:32:25 PM EDT
I have an LMT MRP upper with two barrels and installed mounts for a M4/2000 on each.  The 10.5" shoots great with and without can, adjustment is approx 2" at 100 yds.

The 16" barrel shoots close to the 10.5" without the can, though with the can it shoots 18"-20" low at 25 yds.  Mount or my installation must be bad.... I tried reinstalling mount same thing.  

Please recommend a qualified person to fix.

Hammer
2/19/2009 7:14:31 PM EDT
[#1]
Seperate the upper from the lower on the 16".  Remove bolt carrier.  With the can installed, look down the barrel.  Do you see a clear path or an egg shaped hole?  Does it look like there is a spot where the rounds are hitting?
2/20/2009 6:28:57 AM EDT
[#2]
what kind of barrel is on the 16"?
reason being, I've heard of people putting cans on thin barrels and hanging all the weight on them "droops" the barrel some.  particularly when hot.

just something to consider
2/20/2009 10:15:01 AM EDT
[#3]
It is the same upper, the LMT Monolithic Rail allows changing the barrel by removing two bolts.  I have looked down the barrel with the can attached.  When looking down the edges of the rifling the sides of the baffles are not visible.  

There was a very minor baffle strike.  The baffles on one side look like they've just been touched, and the end cap has a small dimple.

2/23/2009 6:24:52 PM EDT
[#4]
call lmt, they are a stand up company and should take care of you.  If that does not work, contact adco and they will re-thread it for you and check everything.

2/24/2009 6:01:01 AM EDT
[#5]
My LMT barrel is like .020 out of perpandicularity at 6.5" That's pretty awful.  I would guess my experience would be similar to yours- I haven't mounted any cans except the spartans which have a .311 bore.  

The M42000 should not be used until you get that fixed.  The situation is likely a high risk of baffle strikes.  

In a 10.5" barrel... unfortunately... I don't think you can re-cut on account of the length issues.  You may be able to chase threads with a good settup but any way it goes it will be less than ideal- more of a repair than a solution.  Best choice is to sell the barrel.  

LMT should honestly replace the barrels, they suck horribly.  We pay too much for them to have these problems and obviously on 10.5's re-cutting is not an option.

If LMT offers to replace the barrel with one checked and confirmed concentric, let me know as I'll send them mine.
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