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View Full Version : CMMG 20" A2 Gov't Upper 18-Clicks Right Windage to Zero


eric1972
06-02-2008, 5:15 PM
Hi everyone,

I recently received a new CMMG 20" A2 Gov't profile upper, and I took it to the range recently to zero. I used only new Federal M193 ammo and shot off a sandbag. Initially, I couldn't find my bullets and saw that they grouped wide left. After 18 clicks (9 MOA) to the right on the windage, I was able to center the groups. I also had a new TA11 out of the box, and it also required the same amount of windage to zero.

I previously had a Colt AR15A2 and many times qualifying on the M16A2 when I was in the USMC, and I've never required 18 clicks windage to zero (but can't remember now whether anyone else had that many clicks and whether it was acceptable).

I'd greatly appreciate any thoughts members here might have on whether I should send it back for them to look at, or whether this is within acceptable tolerances and won't lead to other problems in the future?

Thank you in advance for your thoughts!

Eric

Army GI
06-02-2008, 5:26 PM
That is pretty strange. Maybe have a gunsmith look at the FSB alignment? The only other thing I can think of is maybe the barrel has been bored off center?

Randall probably has the answer.

bwiese
06-02-2008, 5:31 PM
IIRC, milspec allows something like +/- 13 clicks windage adj. for zeroing.

I'm betting your front sight tower is a tad canted due to overtorquing when mounting bbl.

This was fairly common on Bushmasters in the late 1990s.

CMMG should make it right.

Ronco
06-02-2008, 5:55 PM
I'm betting your front sight tower is a tad canted due to overtorquing when mounting bbl.

This was fairly common on Bushmasters in the late 1990s.

CMMG should make it right.

I'd agree with Bill. Because... I'm having the same problem as OP. Someone told me the barrel should be torqued to 35 ft. pounds (don't know if thatís right) but mine probably has about 90 lbs. torque on it. I wanted to make sure it was tight. Now my RRA NM carry handle rear sight is almost maxed to the left. I'm going to have to loosen my barrel and adjust it and torque it correctly.

Is 35 ft. pounds torque correct?

mecam
06-02-2008, 6:05 PM
Is 35 ft. pounds torque correct?

That should be fine. I have an AR that I torqued at 30~35lbs and everything lined up perfectly so I left it at that. Over 1000rds and no sign of a loose barrel.

Paratus et Vigilans
06-02-2008, 6:12 PM
I'm not sure an over-torqued barrel would cause you to have to use all that windage on your optic to get to zero. I can see it for a canted FSB due to over-torque, but not for the optic.

Something else to think about - - your head position on the buttstock. On my wider buttstocks, like my LMT SOPMOD, the extra width forces my cheekweld further away from the centerline of the rifle, and it takes me a lot of clicks of windage on the irons to zero it for windage. Not an issue for my builds with an A2 buttstock or a basic M4 buttstock.

Just a thought. :)

Bishop
06-02-2008, 6:32 PM
Is it new? When I first got my Stag 2HL, I had to crank the windage hard to the left. It looked a bit obscene. After a few K rounds, I noticed it was off, and wound up pulling it back to the center about 8 clicks. Might just need to settle in.

If not? Who cares. So long as it shoots straight. :) It's just aesthetic.

ocabj
06-02-2008, 7:05 PM
If not? Who cares. So long as it shoots straight. :) It's just aesthetic.

Getting a no-wind zero where the rear sight is as close to mechanical windage zero is not an 'aesthetic' issue. Having your no-wind zero equal or close to the mechanical windage zero as possible allows you to maximize the amount of windage adjustment you can have. This is important when shooting in a high wind at a longer distance.

Of course, if this isn't a mid-range to long-range gun and is only a short-range 'plinking' gun, then I guess it's a non-issue.

eric1972
06-03-2008, 9:30 AM
Thanks for all your thoughts.

It is a brand new upper, only 300 rounds down the tube, so, maybe I've yet broken it in.

I'll also keep in mind my cheekweld as well, a very good point. I think I'll take it out again and see how it goes. It's not a match rifle, so, it's not a big deal, but, I'd rather have everything as "normal" as possible.

Nikola
06-03-2008, 11:48 AM
my CMMG A2 took fourteen windage clicks to zero. I zeroed at 50 yards. As long as you can adjust the sight right, I see no problem. As in nothing I would pay money to fix, especially for a non-competition rifle.