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Posted: 2/16/2010 9:00:43 PM EDT
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I just got an BCM midlength upper and the rear sight has to be drifted way off center to the left to sight it in.
I know the rear sight is fine because I've used it on other rifles and it always centers fine. I think I can see the front sight is a little canted but it's hardly noticable unless you're looking for it. I'm not sure if this is a problem worth fixing because it does work It's just annoying. Should I just live with it? Should I try to send it back? Thanks for the advice in advance guys. |
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Quoted:
I just got an BCM midlength upper and the rear sight has to be drifted way off center to the left to sight it in. I know the rear sight is fine because I've used it on other rifles and it always centers fine. I think I can see the front sight is a little canted but it's hardly noticable unless you're looking for it. I'm not sure if this is a problem worth fixing because it does work It's just annoying. Should I just live with it? Should I try to send it back? Thanks for the advice in advance guys. I know others will disagree, but I had this problem with one of my Colts after I installed a freefloat tube. I simply took a rubber mallet to it and wacked back into its proper orbit. Rifle shoots great now, no issues. 
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How far off center is your front sight? I've got a BCM middy that has a canted front sight, though it's not by too much. I actually didn't notice it until I went to sight it in. I can compensate with my rear sight with no problem. I've just decided to live with it. It doesn't affect my accuracy and I use my EoTech mostly anyway.
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cut it, slap on a free float with bolt on front sight.... issue solved :)
and gives you a reason to buy a ff rail, sounds like a win to me lol EDIT: im sure someone will chime in with the number, but the TM says that its within spec as long as it doesnt take more than X amount of windage to sight in. (i think its 21 clicks but that seems too high to me) |
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My BCM upper has a canted front sight, too. It took 6 clicks on the DD fixed rear to center.
Also, the M4 cut on the barrel extension did not line up perfectly with the cuts on the receiver. Bcm told me that 6 clicks was within specs but they said that I could send it back to them so that they can take a look. The canting on mine was not obvious on the pictures i sent them. I have not sent the upper back to BCM. The rifle has a scope now. Someday, I will put a rail on it. I figured I will fix the canting then. DO NOT use a mallet to force it into place! It may work but not a good thing to do. |
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I am pretty sure Bushmaster told me anything more than 14 or 16 clicks either way on windage is out of spec.I was right at 13 clicks from center on mine.(Bushmaster)As long as it is not noticeable by eyesight,I run a red dot anyway. I just ordered a BCM upper the feed ramps better line up with the receiver or it is going back.
Keith |
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Quoted:
How far off center is your front sight? I've got a BCM middy that has a canted front sight, though it's not by too much. I actually didn't notice it until I went to sight it in. I can compensate with my rear sight with no problem. I've just decided to live with it. It doesn't affect my accuracy and I use my EoTech mostly anyway. It's about 8 clicks to the left to get it sighted in. Is this in spec? I guess I'm leaning towards just keeping it as is. It just bothers me because I'm obsessive I guess. |
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Quoted:
Quoted:
How far off center is your front sight? I've got a BCM middy that has a canted front sight, though it's not by too much. I actually didn't notice it until I went to sight it in. I can compensate with my rear sight with no problem. I've just decided to live with it. It doesn't affect my accuracy and I use my EoTech mostly anyway. It's about 8 clicks to the left to get it sighted in. Is this in spec? I guess I'm leaning towards just keeping it as is. It just bothers me because I'm obsessive I guess. 8 clicks is nothing over 12 or more then get out the mallet |
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Having to adjust a few clicks to get on target is normal. That's just the nature of interchangable parts. If you have to dail it all the way over though, I'd call Bravo Co. They don't have a reputation for excellent customer service for nothing, after all.
Tex78 |
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Quoted:
Quoted:
How far off center is your front sight? I've got a BCM middy that has a canted front sight, though it's not by too much. I actually didn't notice it until I went to sight it in. I can compensate with my rear sight with no problem. I've just decided to live with it. It doesn't affect my accuracy and I use my EoTech mostly anyway. It's about 8 clicks to the left to get it sighted in. Is this in spec? I guess I'm leaning towards just keeping it as is. It just bothers me because I'm obsessive I guess. You are GTG. I read a while back ( in numerous Busmaster bashing threads) that spec was 13 clicks. Some guys had thier peep hard over and still couldn't get a zero. I think my Bushy M4-gery is 10 to the left. It erks me too, but it's a mass produced gun and when you think about it, just a few thousanths at the sight = inches at distance. |
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Anything under 10 clicks and I don't worry about it.
To whoever mentioned the feedramps above. Unless they were literally assembled and then modified/blended, I don't think I've ever seen an upper/barrel extension that were absolutely 100% perfect. If it bothers you, its an easy fix if you have the tools, but its certainly not something I'd send an upper back for. If you have to move it all the way over, then thats a different story. |
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Quoted: Quoted: How far off center is your front sight? I've got a BCM middy that has a canted front sight, though it's not by too much. I actually didn't notice it until I went to sight it in. I can compensate with my rear sight with no problem. I've just decided to live with it. It doesn't affect my accuracy and I use my EoTech mostly anyway. It's about 8 clicks to the left to get it sighted in. Is this in spec? I guess I'm leaning towards just keeping it as is. It just bothers me because I'm obsessive I guess.  |
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Quoted:
I had a couple like that. I loosened the barrel nut, trued uo the barrel and the sight was centered. Too much torque with the receiver in a block can cause the notch to move sightly. +1 Clamp the barrel (not the receiver) in a set of vice jaw blocks (remove the gas tube first) and loosen the barrel nut then re-torque the barrel nut and it will go the other way. Eugene Stoner's original design for AR barrel installation was with the intent that the barrel, not the receiver, be clamped in vice jaw blocks when torquing the barrel nut. Granted it's quicker and easier to clamp the upper receiver rather than the barrel in the vice jaw blocks, and it leaves no aluminum vice jaw block marks on the barrel, but it creates the left front sight base (FSB) cant we constantly see today. Today it is accepted that the receiver be clamped in vice jaw blocks rather than the barrel, which gives us the constant left leaning cant of the FSB . It is pervasive on every upper assembly I have bought in the last 10 years from all manufacturers. Try it and you'll understand what's being referring too. |
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