How many windage clicks from mechanical zero is considered 'in spec'?

[JNG3]

Thank you all for the replies. It seems that there have been many revisions of the requirements over the years based on the upper, general needs of the carbine/rifle and rear sight used. I read the current revision last night and yes there is no longer a requirement for 'centering' the rear sight. However that is because the rear sight is now a BUIS (I assume more than likely the Matech) and not a detachable carry handle. I could pull the barrel and re-install it making sure that there is no cant to the front sight (not that there is any visible cant now) but I think it will be fine as is. Rifle shoots extremely well as is and I don't want to change that.

[Iraqgunz]

USMC was still using carry handles when not using an ACOG.

Thank you all for the replies. It seems that there have been many revisions of the requirements over the years based on the upper, general needs of the carbine/rifle and rear sight used. I read the current revision last night and yes there is no longer a requirement for 'centering' the rear sight. However that is because the rear sight is now a BUIS (I assume more than likely the Matech) and not a detachable carry handle. I could pull the barrel and re-install it making sure that there is no cant to the front sight (not that there is any visible cant now) but I think it will be fine as is. Rifle shoots extremely well as is and I don't want to change that.

[sinister]

The 2009 70599B for the carbine specs a Back Up Iron Sight that still requires 7 revs of motion. The barrel can now have a max of 3 MOA off centerline since the MATECH BUIS is not part of the upper.

[Eurodriver]

Not doubting the spec, but What effect does this have in practice?

I have seen dozens and dozens of M16A4 and A2 carry handle sights require more than the permitted spec for windage.

As a civilian, I see plastic MBUS sights almost jammed to one ear to get a correct zero.

[sinister]

In truth, not a lick. The US Army doesn't monkey with the windage knob in actual practice -- once it's set it's set.

I suppose it comes from whether or not the components were made to certain drawing spec, +/- tolerances.

[lysander]

USMC was still using carry handles when not using an ACOG.

MIL-DTL-63997 is for the M16A2.

The centering requirement is no longer required even in the fixed carry handle versions, it just has to have 7 full turns to go from the right extreme to the left extreme.

[lysander]

The 2009 70599B for the carbine specs a Back Up Iron Sight that still requires 7 revs of motion. The barrel can now have a max of 3 MOA off centerline since the MATECH BUIS is not part of the upper.

That requirement is not quite the same as the windage requirement, and has always been part of the barrel drawing (well, at least since 1988).


Step 92 of paragraph 4.4 reads:

92. Insert a self aligning plug into the bore end of the barrel and measure any angular deviation of the barrel, if any. (Barrel assembly angular deviation)


The barrel drawing notes:

Note 8. A self aligning plug inserted 3.000 [inches] into the muzzle may have an angular deviation from a theoretical axis established by -K- [outside diameter at the FSB journal] and -L- [outside diameter at the breech swell] of 0° 3' maximum


Basically, it measures the parallelism of the last three inches of the bore axis to the outer surface.

[jmreagan]

Weapon in question is a semi auto M16A4 clone with a BCM carry handle that I built.

I have read the publication for the M4A1 (have it right in front of me) MIL-C-71186 and the section 3.4.6 titled 'Targeting and Accuracy'. I assume that this document applies to any flattop. Having trouble making heads or tails of the actual requirements. My clone required 9 clicks right of mechanical zero to perfectly zero left to right at 25 meters. I assume it will also be very close, if not dead on in relation to windage at 91.4 meters. The 9 clicks I required is within the 12 clicks specified in the document but there seems to be more to it than that when I read section 3.4.6

OP, while yes it's true and zero'd now... 9 clicks would bother me too even though it certainly won't affect function. I had a PSA 14.7" CHF barrel assembly that it's FSB was canted so bad to the left it took well over 20+ clicks to zero. Even the barrel extension's M4 cuts were canted far out of time with the lower receiver cuts. I had to post pics of it in their Industry Forum on another site before PSA would take it back. So, the replacement came; and although it was way better cant/ barrel extension timing wise; the FSB was still canted to the left. So, I put a slight notch in the upper receiver's (BCM), index pin slot, on the left side of said slot if looking at the receiver from that back to front where the barrel would be pointing. Then I inserted the barrel and placed an improvised shim, (small folded piece of aluminum from a Ginger Ale can), to hold the barrel in it's intended place so it wouldn't rotate out of the timed position while torquing the barrel nut. I finished the install of the barrel and then used an aluminum angle iron atop the center of the receiver's Picatinny rail. The angle iron ran down the top of the receiver in the middle of the barrel and thru top dead center of the FSB atop the front sight post. Even the M4 cuts on the barrel extension now matched/timed perfectly with the lower receiver cuts as well. It only took about 20 minutes from start to finish. Next it took a trip to ADCO to have the FSB pinned/welded. Finally at the range it only took one click to the left of dead center to zero the rifle; of which I was extremely pleased. This rifle has become mine and the wife's back up go to rifle that we love. There are some youtube video's that will show you exactly how to do it OP if the 9 clicks really bothers you. Hope this helps...