Optics Entropy

[Admiral Unknown]

So, i have been a lurker for quite some time, but have reached a point that i require some advice.

I have built a second upper for my ar recently, but have had a frustration time with optics.

So, i am a dealer and have been eyeing this 4x acog on the shelf for a while but didnt want to drop that kind of $, even with dealer pricing. So, i order a cheap chinese knockoff. I get it in the mail, $100 shipped, and was very surprised by the quality. Things were looking good. So i mount it, and all my hopes of using this thing fade away with alacrity. I cannot adjust it over to the left far enough to boresight it.

So, i farnarkle with it a bit, and after a while i give up on it. A little dissapointed, but i knew i was rolling the dice by buying an imposter.

So, ever persistant, i decide to deep six the chicom acog and return to good ole irons and mount a set of folding tritium irons from Troy. To my dismay, i canot get these adjusted far enough to the other side!

Im scratching my head here, hoping to beseech the wisdom of fellow booliteers. Any ideas why my sights are so far off in OPPOSITE directions?

[Admiral Unknown]

Oh yeah, forgot some specs.

16" mid length 223 wylde 1/8 stainless bbl from aero

Troy claymore break

Wmd nibx bcg

15" troy alpha handguard

I do some smithing on the side, so i did double check that the bbl nut was torqued so the handguard a level perfectly concentric to the rail on the receiver.

I did have the thought to wayside the irons as well and replace them with a 1-4 vortex viper pst, but am worried i may run into the same problem.

Any help here would be greatly appreciated

[salty dog]

Just a guess here, but I would suspect whatever the sights are mounted to. If the rail/base/whatever, is cocked, it could be pointed way over to the right, but the portion to which the rear iron mounts may be hanging out on the left side. Just a guess.

[Admiral Unknown]

Just a guess here, but I would suspect whatever the sights are mounted to. If the rail/base/whatever, is cocked, it could be pointed way over to the right, but the portion to which the rear iron mounts may be hanging out on the left side. Just a guess.
I did try mounting the chicom acog on something else, and have now concluded that it is junk. I know, its my own fault for not spending the $ on a trijicon, but im still baffled by the irons.

It got to the point i got out a laser level to see if the rail or handguard was crooked. This is an A3 upper, but it wouldnt hurt to check. Sure enough, everything is perfectly aligned. What are the odds that my barrel is severly goofed? I did shoot it, and it grouped beautifully. It was about 3 feet off at 25 yards, but had no problem dropping lead within 1/4"

Im at a loss here. It just doesnt make sense

[Moonie]

Did you square the end of the receiver before installing the barrel? They can be off, wouldn't think it would be that far off, what brand of upper receiver was it?

[Smoke4320]

sounds to me like either the barrel is bored off center or the receiver face is not square

[Yodogsandman]

Bad boresighter? Start shooting close. Shoot, adjust, shoot, adjust.

[Admiral Unknown]

That could very well be the case. I was begining to think the onlt logical explaination was my sighting plane waa cursed by the Archmage Feinstein.

I went cheap with a Unites Armory upper. I will pop my barrel off and look after work

[popper]

Barrel & receiver alignment. Don't know how to fix it though.

[geargnasher]

Pull the stock, tube, bolt/carrier out and check the barrel/sight alignment with your eyeball. A cleaning cradle and the screw on a light switch cover across the room works for me.

Gear

[country gent]

Is the front sight on the gas block? Are the rails truly straight to the bore? Threads and face of reciever square, true, and concentric to the centerline of the reciever? Gas tube not in a bind thru nut reciever joint? Some picatinny rails dont work well with weaver bases. If sights are mounted on gas block are the taper pins locating it corectly? On modification done was to cut four flats in the barrel ( where the pins would go thru) Tap the pin holes and use 4 set screws to center locate the sight. How does the crown muzzle look? concentric and square to bore? 3 ft at 25 yds is alot to be off am guessing its a combination to be out that much. Check to see if barrel extension is sitting on shoulder face and not on a radious or burr also.

[Moonie]

I have one of these to square the front mounting surface of an AR upper:

http://www.midwayusa.com/product/810457/ptg-upper-receiver-lapping-tool-ar-15

Works very well.