CMMG upper shoots a foot to the right?

[ekengle]

The upper is a 16" lightweight mid length with a FSC556 on the muzzle. I have been unable to zero this rifle at 50 yards. I have tried using Rem UMC 55gn, Wolf 55gn, M193, Black Hills 55gn, & various reloaded 55s, 68s & 75gn ammo.

I have used a A.R.M.S. 40L rear sight, a Yankee Hill rear sight and an EOTECH 512. All of these sights were zeroed on another 16" 1 in 7 twist rifle. I tried all of them on a second rifle with the same specs and they were all within an inch or so at 50 yards, but when installed on this CMMG lightweight upper they all had to be moved as far to the left as they could go and it still shoots a foot to the right.

There doesn't appear to be anything wrong with the upper, nothing looks bent or twisted in anyway. I'm not using a rail, just basic handguards. I have contacted CMMG about this and they said they would email me a return label so they can look at it, but so far it hasn't arrived despite 2 phone calls.

Has anyone else had a problem like this? I have been told that the FSC556 will change the POI but I have serious doubts it would throw it that far out of whack.
Any ideas?:confused:

[Jay Cunningham]

Have you contacted CMMG and/or the vendor who sold it to you?

[ekengle]

Yes, twice. They had no ideas on what it could be other than a canted FSB, which doesn't look canted at all, or the FSC556 was causing a problem. They said they would send me a return label by email so I could send it back for them to look at. No email so I called back and talked to them again the next day. Same story, no ideas and they would send me another label by email, 2 days later still no label.
Gonna try one more time on Monday then I will send it back on my own dime and ask for a refund and just get an LMT. I really like the lightweight midlength and don't want to go with a carbine gas system, but I have to have a rifle that hits where I point it.

[ADC]

If you caint get it to shoot with the E-otech then you have a problem, the front sight canting dosent have anything to do with the red dot.
I would remove the muzzle devise and try it, and if you are still having some problems, I would send it back.
Besides it shooting right is it grouping your shots?

[ekengle]

Groups are fine with all types of ammo tried. They are just way far to the right. I am going to try a couple of different muzzle devices tomorrow if I can. I have access to a Yankee Hill Phantom and a DNTC comp and a regular A2. I hope that it's not the FSC556, I really like the way it preforms. The dot just sort of quivers on the target, very little movement at all. I could go with the DNTC if it works but since I own a farm out in the country I actually have a use for the flash suppressor.

[ADC]

So you are saying that with the Eotch you can not get your rounds to impact to center? Have you used all of your windage in the scope?

[skyugo]

all i can think of is an out of spec flat top rail... :confused:

windage on my CMMG is a couple clicks left of center, but nothing crazy....

[ekengle]

So you are saying that with the Eotch you can not get your rounds to impact to center? Have you used all of your windage in the scope?

Both of the BUIS were maxed out in adjustment. The EOTECH did not belong to me and the owner didn't want me to try to adjust it as he didn't want to have to zero it again for his rifle.

[telecustom]

We had this problem with a Colt M4 a while back. The problem ended up being a loose barrel. It seemed solid to the touch but once we locked it into the vice it was apparent that the barrel tension was the problem. My Armour tighted it up and it shot like champ. I hope this helps.

[ADC]

Both of the BUIS were maxed out in adjustment. The EOTECH did not belong to me and the owner didn't want me to try to adjust it as he didn't want to have to zero it again for his rifle.

I have seen quite a few canted front sights on diffrent makes of barrels. It could be your problem, however I have seen upper receivers that were not true and made the barrel out of alignment with the center line of the receiver. I have also seen some slightly bent barrels. All these problems can cause a upper to shoot too far windage or elevation. If you can put a scope on it and it takes too much windage to get your point of aim/point of impact it could be an out spec. receiver or bent barrel.
I always spin my barrels in the lathe and check them for straightness, and check my uppers too.
Hope this helps...............AD

[ekengle]

Took upper to the range today. I tried every combination of the FSC556, a DNTC comp, and a Yankee Hill Phantom, for muzzle devices. For the sights I used my A.R.M.S. 40L, a Yankee Hill flip up, and the borrowed EOTECH 512 again.

The DNTC comp shot to the right just about as much as the FSC556 with all sights. The Yankee Hill shot to the right also, but not quite as far. It was about 3 inches closer to center than the others with all 3 sights.

Took all 3 comps and all 3 sights and put them on a different upper, (a Bushmaster 16" featherweight 1 in 7 twist carbine) all combinations shot properly. They all were within a couple of inches of each other & were centered as they should be.

I finally got my UPS return label yesterday and will be sending this back to CMMG tomorrow. I am sending it exactly as it was when I first tried it and how I want it set up, with the FSC556 and the A.R.M.S. 40L. I am not sure if I could move an EOTECH far enough to get it to shoot center without work on the upper or not. Either way, I don't really want to do that, if I ever HAD to use the iron sights there is no way to get them to zero even if the EOTECH can.

Thanks for all the suggestions, I will let everyone know what happens when it comes back. CMMG said they like to get repairs like this out in a week if they can, hopefully it is something simple and won't take long.

[Bimmer]

Did this ever get resolved?

Ben

[ADC]

Yea I would like to know if they replaced the barrel?

[wezalsgunsupply]

The advice sent along is right on target. I have used many CMMG barrels with no problem. Although I have mounted them all myself. Slim chance the barrel is out of whack but possible. Probly in the barrel nut torque. And very likely the upper receiver is out of spec. I have used several of their uppers with no problem. I have had a RRA A3 upper that I experianced a similar issue to yours. Did all the things you tried and no luck. Ended up putting a new upper reciever on and it cured it. I beleive it was the rail millings were incorrect. I ended up using that one later with a removable carry handle and have gotten by with it. RRA would not replace because I had mounted it and they would not replace because was not factory installed. Keep on CMMG til you get your answer. I mean you will have to ride them. Been really hit and miss with their customer service lately. Let us all know how it works out.

[Furious]

I'd also like to know what was ever done about this. I have a CMMG 11.5 that fires as accurate as my RRA 16" does.