Need help diagnosing an accuracy issue...

[billybronco]

Entire upper consists of Noveske parts and assembled by ADCO.

Had them drill and pin the GB while they had it.

Spared NO expense. 12.5 Crusader, MUR/Noveske upper and NSR 11 rail. Bolt is Noveske with BCM carrier.

Used MBUS PROs in initial zeroing and began CLOSE. Like 7 yards. 1st shot low and WAAAY left. 5 inches left. Clicked 8 right. 2nd shot RIGHT next to it. I ended up moving this damn rear sight alllll the way slam over until it wouldn't move anymore. STILL not zeroed. WTF???

I've used PMC, Wolf Gold and M193. Same results. Pulled PRO and threw on fixed rear DD. Same issue.

Using a bipod, rear bag and SD-E trigger.

Could it be a mis-indexed barrel nut? I've read that it can happen when the nut is tourqued on so tightly that the index pin moves in the receiver slot. Close inspection shows the upper and rail to be perfectly aligned.

This is probably the most frustrating shit I've encountered in 15 years of collecting, building and shooting this weapon platform.

Finally. If it IS a mis-indexed barrel, will the same results occur when using an optic only?

[556BlackRifle]

As a first step, I'd try another set of sights. Next I'd try some heavier bullets just to see where they hit. If none of this helps look at the crown and index pin but my best guess would be the first two.

Good luck.

[billybronco]

Yeah Roger. I did only replace the rear. The DD was the same height as the PRO. My only point in wondering why I should replace the front sight is because its a windage only issue. What good would a different front do?

Also, as an aside. I pulled the guts outta the BCG and the CH and let the the empty carrier run inside the upper back and forth all the way from read into battery trying to hear and feel for any resistance of gas key on gas tube. Nada. Perfect alignment.

[mpom]

If it was me, I would call ADCO.

[mtdawg169]

Entire upper consists of Noveske parts and assembled by ADCO.

Had them drill and pin the GB while they had it.

Spared NO expense. 12.5 Crusader, MUR/Noveske upper and NSR 11 rail. Bolt is Noveske with BCM carrier.

Used MBUS PROs in initial zeroing and began CLOSE. Like 7 yards. 1st shot low and WAAAY left. 5 inches left. Clicked 8 right. 2nd shot RIGHT next to it. I ended up moving this damn rear sight alllll the way slam over until it wouldn't move anymore. STILL not zeroed. WTF???

I've used PMC, Wolf Gold and M193. Same results. Pulled PRO and threw on fixed rear DD. Same issue.

Using a bipod, rear bag and SD-E trigger.

Could it be a mis-indexed barrel nut? I've read that it can happen when the nut is tourqued on so tightly that the index pin moves in the receiver slot. Close inspection shows the upper and rail to be perfectly aligned.

This is probably the most frustrating shit I've encountered in 15 years of collecting, building and shooting this weapon platform.

Finally. If it IS a mis-indexed barrel, will the same results occur when using an optic only?
Use a straight edge, like a 3' long level and hold it along the edge of the picatinny rails. Check both sides, and see if the rail is straight and true compared to the upper receiver. Another quick visual check is to see if the barrel is centered inside the rail or not.

[BooneGA]

You spared no expense on parts but had ADCO assemble it? That is likely your issue. I had similar issues when they built a rifle for me, it turned out the gas block was touching the rail causing a myriad of issues.

Get in contact with them and have them fix it.

Rick

[dramabeats]

You spared no expense on parts but had ADCO assemble it? That is likely your issue. I had similar issues when they built a rifle for me, it turned out the gas block was touching the rail causing a myriad of issues.

Get in contact with them and have them fix it.

Rick

Everyone here swears by ADCO, have you had a different experience besides your gas block issue?

[T2C]

How do the MBUS Pros sights work on another carbine? Are they close to zero windage?

It takes a lot of windage adjustment to compensate for a 5" POI error at 7 yards. Can you put a pair of levels on top of the receiver and the gas block to verify they are properly aligned?

If it were mine and there was a problem, I would not dismantle anything beyond removing the bolt and carrier. I would get on the horn to ADCO and have them make it right.

[BooneGA]

Everyone here swears by ADCO, have you had a different experience besides your gas block issue?

There were quite a few threads a while back dealing with guns ADCO had messed up on this forum (I believe) and others.

I went with them because one of the employees was very helpful with discussing what I wanted. They sent me and improperly assembled rifle. I honestly do not remember the exact details of all of their other mistakes, but I will not use them gain.

Rick