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Posted: 7/8/2003 7:42:24 PM EDT
I have a Colt 6721 upper that requires 17 inches of windage to the left of center to bring the strike of the round to the center of the target. The elevation only requires two clicks. I am wondering how many clicks are acceptable or unacceptable. I remember from my Marine Corps days the fact some of the A2s required 7-10 click adjustments.
Link Posted: 7/8/2003 10:30:05 PM EDT
[Last Edit: 7/10/2003 2:33:16 AM EDT by Tweak]
Just to speed things up A1 or A2? assuming A2 but gotta ask. 17" of wind at what range, or how many clicks of wind? A2 Milspec put the rear sight within 5 clicks of center wind when rounds are impacting ON (not centered on) an 11.6" wide 100 yd target. So add that 5 clicks to the 11.6 1/2MOA (A2) clicks it would take to get to the center (think before posting) of the target assuming worst case scenario and you get 16.6 clicks of wind max. The above is for the A2 rifle, haven't checked the spec for the M4s. Bc I go by the rule: "If it bugs you it's an easy fix." What's the lineage of this upper, straight from Colt? Built by a friend? Bought off a gun show table? [edited to add the math and dele the incorrect spec for the M4 to avoid confusion]
Link Posted: 7/8/2003 11:26:10 PM EDT
OK, checked the specs for the M4A1, same 5 clicks allowable, only diff is the 100 yd test target is 16" wide instead of the 11.6" for A2. So, given the 5 clicks plus the 11.8 clicks (0.68MOA clicks on A2 carbine sight radius) needed to get to target center you're looking at 16.8 clicks allowable.
Link Posted: 7/9/2003 11:47:01 AM EDT
the upper is directly from Colt with no modifications. It is an A3 flattop configuration with A2 sights.
Link Posted: 7/9/2003 4:10:42 PM EDT
Third line down, my first post this topic. Hey, where's Dano's post?
Link Posted: 7/9/2003 6:01:13 PM EDT
Dano was up too late last night and gave up trying to proof the post once daylight broke. For the rest of you that didn't catch my post, It was basically to use a leather mallet and drift the barrel in the receiver by holding the receiver and giving the bottom of the sight tower a few firm blows to drift the barrel (sight/barrel back into index with the rear sight/bore plain), instead of cranking the rear sight all the way to the left. The barrel needs to be rotated clockwise (right, if your looking down the sights from the butt stock. Also, this is Tweaks method, mine is to just loosen the barrel, bore sight and tighten the barrel like it should have been done from the start, then a whack to fine tune. At 34 clicks off center, the barrel was not installed even close to bore plain index. P.S. It looks like bushmaster fired their installer of loose/broken carrier keys, and he found a new home with Colt.
Link Posted: 7/9/2003 7:06:49 PM EDT
Link Posted: 7/9/2003 9:58:38 PM EDT
Well, "my" method, also that of BFI, Accuracy Speaks, and others, strenuously avoids using bad parts so the worst whacking I've had to give was two light taps equal to ~ 14MOA, or 10cm at 25m. If your sights are waaaaay off then I'd look closer at the parts. If you drive the barrel too far over you'll misalign the gas tube and mistime the barrel extension.
Link Posted: 7/10/2003 1:53:05 AM EDT
Tweak, So we both agree on that if the upper is built correctly (with in-spec parts), then all that should be needed is some fine-tuning to zero out the sights. The only thing that makes me wonder is that he said that the upper came directly from Colt. Somehow I think that there was a middleman between Colt and Tactical, and the barrel was swapped out. Might be a good time to pull the hand guards and look for Colt’s CMP marking to make sure that the barrel is in fact a Colt. Or at least pull the barrel and make sure someone using a barrel vise and too much pressure on the barrel nut to seat it did not bend the extension pin over, and it is causing the problem.
Link Posted: 7/10/2003 2:31:39 AM EDT
Totally agree, that's why I was surprised you had dele you previous post as it was the answer to what would obviously be tactical's next Q. I, too, wonder if there was a middleman but Colt isn't infallible. Whether there was or wasn't one is of little matter (in this case) tho since a poorly installed barrel can't compete with bent barrels, crap chambers, or missing parts on ARs as available from some manuf's. :-)
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