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Posted: 11/26/2006 4:58:45 PM EDT
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Took out my BM X15E2S M4 for the first time today. Using military 25m sighting targets at 25 yds the first groups were to the right edge of paper and high. I kept adjusting to the left until they were center high, then adjusted front sight until they were centered. Backed up 75 yds and shots were off the paper, kept adjusting until they were on and high but they were back to the right. Finally got height correct but had to keep pulling rear sight to the left. Result is gun is sighted but the rear apeture almost against the carry handle frame. I'm shooting my 55g fmj reloads. Its this a BM tendency or am I simply blessed with a gun that wants to shoot way to the right? FYI, don't start the "you can't shoot straight" shit cause I'm retired Army, teach precision air rifle at JROTC, and have two other AR15s (Colt) that shoot straight. |
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I have 2 bushmasters, 20" and 16". Seems both shot high while trying to sight in at 25yds. Seems I had to turn the front sight post so it was way higher then normal. I shot expert in the marines so I know sight alignment picture etc. just like you do. However my eyes just do not focus on the rear aperture very well anymore. So it may be my eyes causing the problem. Both have the removable carry handle which means according to bushmaster. the front sight post should be .040 taller then a fixed carry handle A2. which will help lower the grouping without unsrewing the sight post. I don't know how to check the sight post to find out if it is correct. But with my Eotech or scope. I found both rifles to be very accurate. I don,t know if this helps you axl. Maybe we both have a problem.hock.gif |
I just went through the same thing with my Bushy, but low & left on every shot. I took it to the firehouse I work at & had a couple of my guys who have battlefield experience with the rifle lookm at it. We found that the rear sight is actually turned to the left just a bit. When looking down at it, you can turn it straight, but it springs back into it's original position as soon as you let go of it. We're going to take it apart & see what's going on with it (torque issue?).
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Sounds like you have the patented Bushmaster misaligned front sight base. Send it back to them and tell them to replace it. Don't let them try to repair it, make them replace it. |
Nothings wrong....your rear sight is normal. |
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The front sight post ion mine is also way higher than normal, there is very little spring tension left on the post at all because its all the way up. At least mine hits where I aim it but it just looks wrong with the rear apeture all the way over to the left. "Sounds like you have the patented Bushmaster misaligned front sight base Yup. That must be it. Anyone who has had it replaced please advise. Thanks |
The sight is supposed to be turned like that. That's not your problem. |
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Really, I read alot of your posts before becoming a member & I know you're very knowledgable - I tell my jarheads we're not taking it apart now  - Better BSZ & start over again, huh!
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Seriously? I have forgotten the exact cause, but it has been posted here quite a bit. http://archive.ar15.com/forums/topic.html?b=3&f=118&t=252568 http://archive.ar15.com/forums/topic.html?b=3&f=66&t=269433 http://archive.ar15.com/forums/topic.html?b=3&f=4&t=276957 http://archive.ar15.com/forums/topic.html?b=3&f=66&t=268833 http://archive.ar15.com/forums/topic.html?b=3&f=66&t=271324 ETA: I got tired of copy/paste. Suffice to say there are more of them, if I had expanded my search and looked further back. IIRC the problem really came about around the time the ban ended and Bushmaster was cranking them out. |
| Thanx dport - and its funny you say 200 years ago you would have been a pirate - I've been telling my friends that for years (& they agree). If I was smart enough to use photobucket I'd send you a pic of the art on my Fire Depts Blackwater Dive/Rescue team. We even got Edward Teach's flag on the left breast (only pirate dudes get it though)! |
A severely canted FSB can be noticed by simply looking down the length of the rifle. A slightly canted FSB might be harder to detect, but can be compensated for with minimal windage adjustment. What’s perceived as a canted FSB could also be an indicator of an over torqued or out of index barrel. |
The part that has me wondering, is where you said you had it set .... then it just seemed to 'stray' off center again. Sounds like something's loose .... maybe the barrel nut. |
Yup Thanks for the compliment.The reason the sight is springloaded like that is that if the sight were designed to be rigid, it might loosen. Better to have it springloaded but moveable (so it can take some abuse and return to the right spot) than rigid and then have it get knocked out of alignment and stay there when it takes a good hit. |
| all my A2 rear sights give a little left but its still straight.Ive seen some where it realy springs left so that its not staright.I know people have says it dont matter but I have nohing to gauge it by as mine are straight even with a little movement.Ive notice the same thing with removable handles I have one thats staright with play and one thats left and it just looks like too much material might have been taken off during finishing.Ive shimmed them using jb weld on the right side on the receiver..just a thin beed.Let dry sand down and paint black and the sight fits right. |
Well, yes and no. A few years back a lot of Bushies had this problem beacuse the assemblers were getting too ham handed in screwing down the barrel nuts, and the barrels were being slightly tilted in assembly. Remember, it doesn't take much for the steel locater pin on the top of the barrel to dig in to the aluminum of the upper receiver; and in only takes a couple of thousanths off kilter at that point to make a signifiacant difference in point of impact. By way of prediction, if the assembly is done with the upper receiver clamped (the current vogue), that pin will dig into the left side of the locater channel, and the piece will shoot to the right. If the "old fashioned" type assembly with the barrel clamped, the pin will tend to dig into the right side of the channel, and the piece will shoot to the left. Let me repeat; it only takes a couple off thousanths of digging into that uppers channel to cause a signicant off center point of impact. I thought Bushie had fixed the problem, but apparently it's still going on  That's one of the reasons I build my own ARs
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I have heard of it, but like Arokie, have never seen it on any of the BM rifles or uppers I have owned. |
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Any upper I have bought from BM was on the paper right out of the box and only needed very minor adjustment. I'd suggest giving them a chance to correct it. They may let you send just the upper so you can ship it cheap. Because the AR rear sight base is not adjustable, most all of them will need the aperture to be set a few clicks one way or the other, but never touching or nearly touching the base - that indicates to me something loose, bent or out of index. Edited to add the following off the BM site. I think this explains the problem and solution. ***This is a problem that took us some time to figure out but it is so simple, we're kicking ourselves. The little index pin that lines up the upper and lower is very soft, so that it can shear off if the barrel is over-torque. This is to prevent damage to the receiver when barreling. This pin will distort slightly before it snaps, and this slight distortion is enough to create the excessive windage you describe. A new pin costs only $1.50 and removing the old pin is as easy as grabbing onto it with vise grips and twisting it up and out. Drive a new one in and try the upper on. The pin may shear when you try to remove it, but they are easy to drill out. Just be sure not to drill into the barrel extension. A new pin will be like having a brand new barrel (as far as the receiver is concerned, it is new) and that windage problem should disappear.*** |
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