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Posted: 1/21/2006 2:28:58 PM EDT
[Last Edit: 1/22/2006 6:08:58 PM EDT by Buck_Naked]
I have an LMT 16" upper that I am having accuracy problems with and need some help in trying to figure out what the issue is.

I bought it last year, but didn't have the opportunity to shoot it much until fairly recently, and most of it has been at relatively short range. I have taken several classes since Oct., but most all of the shooting has been 25 yards or less. The accuracy at short distances has been good enough that it didn't cause me much concern. Occasionaly when the distance was stretched to 25 to 50 yards, the groups started to open up, but I attributed it to poor shooting on my part.

This past weekend I had a class that did a little distance work, and this is when I began to question the rifle more than myself. We shot at about 100, 200, and a little over 300 yards. I was unable to get a consistant hit while everyone else was 'clanking steel...'. I was a little frustrated and a little embarassed, as I generally regarded myself as a better shot than this. With my Colt 6721 upper, I was able to consistantly shoot less than 2" groups with irons at 100 yards.

Yesterday I was able to go to a range and sit down and see what the upper was doing at 100 yards, and I was more than a little disappointed in the performance... I am just still not sure if its me or the rifle, and will have to wait until I get back up to Oregon and shoot it alongside my 6721 and compare the two side by side with the same optics.

Essentially the best I could do yesterday was a 5-6" group at 100 yards with either an Aimpoint or a TA31F. There was no real pattern to the shots, they were just randomly scattered around the point of aim. I was shooting this in a prone position with the rifle on a pack for a rest, using sound shooting priciples including trigger finger placement, smooth pull and consciously letting the trigger reset, as well as breathing and accurate sight placement. I was shooting Georgia Arms Canned Heat, and thinking it might be the ammo, switched to boxed Federal XM-193, with the results being the same for both. I checked my forend to see if it was loose (KAC RAS II), checked both mounts for the optics (both mounts from Larue) for tightness and could not come with anything that would indicate a problem.

Any further suggestions? What options might I have if the upper should be determined to demonstrate less than expected or acceptable accurcy? I was also under the impression that LMT used Mike Rock barrels, does anyone know if this is true?

Thanks!
Dave
Link Posted: 1/21/2006 3:01:07 PM EDT
My suggestion would be to use a more suitable scope for shooting those groups. Your Aimpoint at best has a 2" dot out there at 100 yards and the ACOG is better, but not as good as a scope with a normal reticle. I've got a TA31F and if I am trying to really see what the rifle can do I break out a "normal" scope. I'm not knocking the Aimpoint or ACOG but trying something else will eliminate this variable.

Another thing I try with most of my new rifles is to buy a bunch of different ammo and see what the rifle likes. I've had some that with one brand shoot into 2" while the same weight bullet from another maker shoots into 1/2".

I'll let everyone else add their wisedom to the pot from this point...

Spooky
Link Posted: 1/21/2006 3:49:58 PM EDT

Originally Posted By Spooky130:
My suggestion would be to use a more suitable scope for shooting those groups. Your Aimpoint at best has a 2" dot out there at 100 yards and the ACOG is better, but not as good as a scope with a normal reticle. I've got a TA31F and if I am trying to really see what the rifle can do I break out a "normal" scope. I'm not knocking the Aimpoint or ACOG but trying something else will eliminate this variable.

Another thing I try with most of my new rifles is to buy a bunch of different ammo and see what the rifle likes. I've had some that with one brand shoot into 2" while the same weight bullet from another maker shoots into 1/2".

I'll let everyone else add their wisedom to the pot from this point...

Spooky


Agreed on trying multiple ammunition brands, types, etc. See which one your gun shoots with best. I would take the top three makes/brands and then weigh the pros and cons of each brand then stock up on the winner.
Link Posted: 1/22/2006 4:15:20 AM EDT
Which LMT barrel did you order with your upper?

There are NUMEROUS options.... Cromo w/chrome lined, Stainless Steel match, SS 5R, as well as several twist rates I wouldn't doubt.

Regardless, you need to match the ammunition to the particular barrel + twist rate for best results...

Get all the various ammo you can find, M193, M855, non M855 spec SS109 (like the British stuff), try some Federal Gold Metal Match and Black Hills of various bullet weights. I would try military ammo first, and then Black Hills.... One particular round may shoot better than another, and it will vary not from rifle or upper manufacturer or another, but very well could vary from barrel to barrel, even out of the same lot. Invariably some are duds and some are one hole shooters, and the only way to tell is by actually shooting them.

Also, ask the particular manufacturer if they have any accuracy standards, and if they do, see about having them test fire and inspect the barrel for problems or possible replacement, and keep your fingers crossed.

You may want to post what your barrel is, twist and type, as well as the ammo you've used, and maybe someone might be able to give you better insight into your situation. Hope you get it worked out!
Link Posted: 1/22/2006 9:18:09 AM EDT

Originally Posted By xenophobe:
Which LMT barrel did you order with your upper?

There are NUMEROUS options..



No there is not. Unless you have a MRP upper the only LMT barrel is a chrome lined 1/7.

Try heavier bullets. 62 grain and up. My LMT will shoot a 1/2 inch at 100 with 62 grain bullets.
55 grainers shoot closer to 2" at 100.
Link Posted: 1/22/2006 9:41:14 AM EDT
Link Posted: 1/22/2006 9:43:21 AM EDT
Link Posted: 1/22/2006 9:47:20 AM EDT
[Last Edit: 1/22/2006 9:49:54 AM EDT by Green0]
How many rounds through the barrel?

If you are betweend 6Kand 10K or above that accuracy is close to typical of what has been my experience.

If not you may have a loose barrel and need to re-torque the nut. The FH could be over-torqued but I don't think that could ever have as great an effect as what you are talking about.

With a FF handguard that is pretty poor performance.

Have you tried having someone else shoot it to see how they group? Maybe the TA31F just isn't working out for you. With an aimpoint I wouldn't expect groups better than 2-4inches at 100yds as I wouldn't even attempt accurate bench shooting with it. No point the way I see it. The ACOG should be able to group under 1.25MOA with an M4 barrel free floated and a low round count. IE under 700rds without abusive fire schedules.


Another long shot- if your forend is touching the handguard cap that could effect accuracy but shouldn't be able to happen.
Link Posted: 1/22/2006 11:38:38 AM EDT
+1 on trying black hills stuff. I bought a box of BH 55 grain for my LMT 14.5", and it would shoot circles around my XM193, even at 25 yards.
Link Posted: 1/22/2006 1:40:47 PM EDT
My experience with Georgia Arms Canned Heat was the shotgun effect also. It's "go bang" ammo, IMO, and results definitely vary. Not sure why the subsequent factory ammo did that, though.
Link Posted: 1/22/2006 4:10:08 PM EDT
[Last Edit: 1/22/2006 4:13:56 PM EDT by Buck_Naked]
Thanks for all the responses...

The barrel is an LMT 16" chrome lined barrel, with a 1 in 7 twist. Between the 4 classes I have shot with it, I have about 6K rounds through it. While the round count is a little high, I have never abused the gun with mag dumps or blasting away...

I wish I would have tested it more extensively before shooting that many rounds, but didn't get the chance... I was living in California and kept the rifle over in Nevada, and didn't get to shoot it as often as I would have liked. I had a 3 day class with Jeff Gonzales, as well as a couple of classes with a local Southern California instructor that accounted for all the rounds.

I have a couple of boxes of Mk. 262 with me, and will give those a try and see what happens.

As soon as I get back up to Oregon, I will see what someone else can do with the rifle, and throw the optics on another upper and shoot them side by side. Apples to oranges, but I have put 5 shots into one ragged hole with a borrowed precision rifle shooting with the same techniques as I used here, but letting someone else shoot it as recommended makes sense.

Taking into account the number of rounds through it, would one expect to see a significant degradation of accuracy in that many rounds witha chrome lined barrel? I thought the service life would be much higher than that...

Thanks!
Dave

Link Posted: 1/22/2006 4:41:53 PM EDT
Link Posted: 1/22/2006 4:50:05 PM EDT
[Last Edit: 1/22/2006 4:53:15 PM EDT by wildearp]
I had the same issue with an LMT upper I bought, installed on a Bushy lower. It seemed to shoot the worst of anything I had. Not terrible, just not as good as I would like. I planned to swap on my match lower and try it out, but never got the chance. A fella on the board was doing some $20 trigger deals around Christmas time.

Fact is that the Bushy lower I traded for on the EE had the classic 5 minute trigger job. When I pulled the works out to send them off for a pro job, I found the sear surfaces were very nasty, almost destroyed, and the hammer had started to cut into the disconnector.

It was the lower causing the accuracy problem, instantly fixed with stock springs, and a professional trigger job performed on a jig.

Some folks can shoot well with a bad trigger. If you get spoiled with a really good trigger, the bad trigger will become a nightmare.

Do you have a lower to swap out? Are you capable of pulling your hammer and trigger and performing an up close inspection?
Link Posted: 1/22/2006 4:51:20 PM EDT
As stated above, try some match grade ammo. A few months ago I tried my LMT with some Fed 77 gr from ammoman.com and got 1.25" consistently from a bench at 100 yards with an EoTech. When I tried unsupported the groups streched out to 8" and only a few groups were below 2".
Link Posted: 1/22/2006 5:04:21 PM EDT

Originally Posted By new-arguy:
6k rounds out of a chrome lined barrel isnt a lot. I would doubt the round count has much to do with whatever it is thats going on.



I agree. Round count shouldn't be an issue. I'd start to check the barrel closely for wear at 10k and go from there. I'd expect at least 15k from a quality barrel and 20k from a pampered barrel - for close quarters accuracy, anyway. N/A to you 0.000025 MOA paper punchers.
Link Posted: 1/22/2006 5:23:12 PM EDT
make sure the barrel is on tight
Link Posted: 1/22/2006 5:29:36 PM EDT
I also say try different ammo. I have not experience with canned heat but have not found XM193 to be real accurate in the rifle I tried them out of. Not that it wont in others,but that's just what I found in the particular rifle I tried. There is one loading that was very accurate in 2 of the uppers I had and that was the Black hills Blue 52 bthps. There are alot of choices though. Enjoy the journey.
Link Posted: 1/22/2006 5:32:52 PM EDT

Originally Posted By k9dpd:
make sure the barrel is on tight


+1
Link Posted: 1/22/2006 6:01:18 PM EDT
[Last Edit: 1/22/2006 6:09:48 PM EDT by Green0]
I wouldn't expect better than 3MOA at 6K. M4 profile.

based on that the rifle isnt too far off. Factory new a good M4 profile will do 1.25MOA with 55grain ammo that's floated too. It doesn't have to be abused at that round count to see accuracy deterioration; the barrel gets pretty warm just firing 40-80 rds and a range training environment could easilly have you shooting that in a couple minutes of a 45 minute session.

The ACOG and a good trigger would be nice to evaluate accuracy if you were really concerned which it appears you are. If you have a lower with a match trigger swap the upper over there when you do the test.


"20k from a pampered barrel "

Those are high expectations. Out of chrome lined I think that kind of expectation for any semblance of accuracy at 20K is rediculous. The stainless 5R's and stainless polygonals might do 2MOA or better at that but I wouldn't expect anything more than bullets leaving the barrel of a chrome lined.
Link Posted: 1/22/2006 10:56:06 PM EDT
Personally, I haven't found the XM193 ammo to be all that great, good plinking ammo, but if you're shooting for accuracy, it's mostly a lost cause. We sell it along with the wolf and norinco stuff for $4 a box, and I haven't done any testing against those others, but the people coming back to buy more seemt o be buying the wolf and norinco garbage over the Federal. Go figure.

I don't have an LMT upper, but my 1/7 seems to really like the 60g V-Max and the 68 grain match... no real scores for accuracy, though I could probably take some real measurements next time I'm out at the range...
Link Posted: 1/22/2006 11:41:12 PM EDT
check bbl.
all mounts and hardware
more precision shooting pratice
better ammo
bag the rifle and see what it does
Link Posted: 1/23/2006 8:58:35 AM EDT
My bushmasters 1/9 twist shoot the ss109 BULLET better than the 55grM193 type dont know why but it does!

try a longer bullet for your 1/7 twist like M855/SS109 or 69etc
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