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Posted: 11/18/2003 4:44:39 PM EDT
I'm new to the #40, only being familiar with the M-16A1/A2 sights. I,ve read all the posts on zeroing the #40 and they all tell me to use the large aperture. I can'nt seem to hold a decent enough size group,(1"-2")with the large apeture for zeroing purposes. I read somewhere on the web that the military uses a plastic insert that clips into the large apeture on their #38 swan sleeves to help them with this. Any ideas would be greatly appreciated.
Link Posted: 11/18/2003 6:02:15 PM EDT
You are confused. The #40 has the very same aperatures as an M16A2 rifle! The little bitty plastic thingy that always gets lost is from the old single aperature on the KAC 300 meter folding sight. Which do you have? If you have a #40, just flip to the small aperature per standard M16A2 zero procedures that you say your familiar with. Jack
Link Posted: 11/18/2003 7:27:24 PM EDT
I just picked up a new Bushmaster A3 upper with an A.R.M.S. #40 and was told that I also needed a higher front site post to correctly zero. I've seen plenty of posts that say you don't need it though. I was so happy that they had a 20 inch 1/7 twist gov't profile barrel I told them to go ahead and install it, only cost $5 bucks so no biggy. But if you still have trouble zeroing that may be a factor. Of course I haven't had the time to zero mine yet so I don't have any first hand experiance. Welcome aboard again.
Link Posted: 11/19/2003 6:03:23 AM EDT
Originally Posted By phobia: I just picked up a new Bushmaster A3 upper with an A.R.M.S. #40 and was told that I also needed a higher front site post to correctly zero.
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It seems some people do need the taller front sight. However, many of us (myself included) have not needed it. I've installed an ARMS #40 both on a 20" & a 16" and had no zeroing problems with the standard front sight.
Link Posted: 11/19/2003 12:23:55 PM EDT
Yes, it is a #40, and I ended up zeroing with the small apeture on a 300m M-4 zero target at 25m. Before I added the aimpoint and #40 I had a detachable carry handle mounted,I found that after I zeroed with that combination, the front sight post was so high that the threads were almost exposed. But it did zero. Since then I have replaced it with the taller post, and it works fine. Thanks for the help.
Link Posted: 11/19/2003 5:16:07 PM EDT
Only short barrels (carbines) not the (rifle) length made by Bushmaster, might need a taller front sight post. That's because Bushmaster use the same sight tower from thier rifles on the carbine too, saves money. The Gov't model weapons that Colt make have two dif ht's., because a carbine barrel needs a taller front sight houing, do to the front sight being closer to the receiver. (Trigonometry) dictates that the closer you are to the receiver, the higher the post must be. Good shootin, Jack
Link Posted: 11/19/2003 5:17:25 PM EDT
Only short barrels (carbines) not the (rifle) length made by Bushmaster, might need a taller front sight post. That's because Bushmaster use the same sight tower from thier rifles on the carbine too, saves money. The Gov't model weapons that Colt make have two dif ht's., because a carbine barrel needs a taller front sight housing, do to the front sight being closer to the receiver. (Trigonometry) dictates that the closer you are to the receiver, the higher the post must be. Good shootin, Jack
Link Posted: 11/20/2003 11:40:10 AM EDT
For 5 friggin years I don't know why my bushmaster M4 needs a tall c7 front site. When I called BM 5 years ago, they blame it on GG&G!! Now we know the truth. BM is the culprit!
Link Posted: 11/20/2003 1:21:33 PM EDT
Bushmaster make great clones, but they missed the boat on this issues as the didn't do the R&D that Colt did. Jack
Link Posted: 11/20/2003 11:25:45 PM EDT
Originally Posted By 3rdtk: Only short barrels (carbines) not the (rifle) length made by Bushmaster, might need a taller front sight post. That's because Bushmaster use the same sight tower from thier rifles on the carbine too, saves money. The Gov't model weapons that Colt make have two dif ht's., because a carbine barrel needs a taller front sight housing, do to the front sight being closer to the receiver. (Trigonometry) dictates that the closer you are to the receiver, the higher the post must be. Good shootin, Jack
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I don't think that is entirely correct. Colt uses an FSB with the "UP" flat ~.040" higher on ALL barrels intended to be installed on flat-top upper receivers. Their carry handles are also taller. When using a rear sight built to the taller spec (such as the ARMS #40 or Colt carry handle), you may need a taller front sight post.
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