A2 carry handle sight - windage adjustment. How much is too much?

[neil0311]

Without getting too long winded here, bought a complete M16A4 style rifle last spring from a mfg everyone would recognize. Couldn’t get a BZO. Sent the upper back and the mfg said they adjusted the front sight which I assume was canted.

I can zero the rifle now (using a Marine style 25 yard BZ), but doing so requires me to crank the windage adjustment on the carry handle rear sight almost completely to the left (there are a couple of clicks left). The POI is on target.

Is that acceptable and in spec, in terms of quality that someone should expect for a AR-15? Am I being too picky? If it zeros, just be happy and shoot it?

[markm]

Hell no. You can't adjust the front sight. The index pin on the barrel extension and the FSB are permanently where they will always be.

There's a spec for the military's acceptance I read somewhere along the way. It's like 10-12 clicks off of mechanical zero. I had a bushmaster upper receiver that was like 10 clicks off of mechanical zero, and I replaced it. I knew it was the upper because I'd had that barrel work fine on another upper. Eff that!! I trued the receiver face and it got like 1 more click worse. No way. I can't live with that slop at all.

[HKGuns]

I'd get a new upper as it sounds like it is still clocked to me.

[markm]

There are potential problems beyond the obvious eye sore of a wonky upper half. I Don't know why the bushcrapper upper was crooked, but if the bolt isn't locking into the barrel perpendicular, the lugs aren't locking evenly and correctly.

[HKGuns]

There are potential problems beyond the obvious eye sore of a wonky upper half. I Don't know why the bushcrapper upper was crooked, but if the bolt isn't locking into the barrel perpendicular, the lugs aren't locking evenly and correctly.

Yep and if there are no M4 RE cuts, as is likely the case with an "M16", it would be hard to recognize a clocked RE / Barrel / both.

ETA: As a comparison, both of my recently acquired Colt LE6920's required only 3-5 clicks of adjustment to be dead on at the range when zeroed.

[neil0311]

OK you folks convinced me. Called, got an RMA, and put the upper in a box and dropped off at UPS to go back to the factory.

Requested a replacement but I assume I have no real say. If they claim it’s fixed and send it back to me, I can’t do much except complain and never place another order from them again.

[Humpy70]

I got a new HBAR in 90 and when I zeroed it at 100 yards I had two clicks left. I called Colt, they said to send it back and I did and they put on a new barrel. It is not uncommon to get a crooked bore internally.

[markm]

If they return it and there's no change, you could try another upper receiver. That was my issue. I just happened to know it because they barrel was in another upper without the problem.

However if the FSB is reamed out of top dead center, there's no fix that I know of. The index pin/barrel extension is nearly permanently in place, and the FSB ream job can't be adjusted.

[DG23]

If they return it and there's no change, you could try another upper receiver. That was my issue. I just happened to know it because they barrel was in another upper without the problem.

However if the FSB is reamed out of top dead center, there's no fix that I know of. The index pin/barrel extension is nearly permanently in place, and the FSB ream job can't be adjusted.

Pretty sure that can be tweaked some. Slightly oversized taper pins and...

Uppers like the one you mentioned can be trued up as well with shims on the one side.

[markm]

Pretty sure that can be tweaked some. Slightly oversized taper pins and...

Uppers like the one you mentioned can be trued up as well with shims on the one side.

No in spec gun I've ever worked on had any play in the index pin notch... definitely not enough to make up for a windage issue. Maybe a couple thousandths, but they generally lock up with little play at all.

And there's zero room for taper pin adjustment that I can see. I mean... that FSB goes on ONE way, exactly where the pins and FSB were reamed. A small pin would just seat deeper, and a larger pin more shallow, but the holes line up one way.