View Full Version : Help determining if my FSB is canted?, Newbie post.
Hey guys, a FNG here. I already posted this on another AR forum because it took over a week just to be able to post on here. I got a few responses, figured I'd pick everyone's brain that I could.
I recently finished my first AR build this month. I've been selling guns at a major retail sporting goods chain for 6 years now and finally decided to buy my own instead of looking at them all day.
I sighted the weapon in this past weekend and ran into a little issue. My rear BUIS windage had to be clicked over to the left 13 clicks from center. Is this too much?
When I bought my upper, It was setup for clam-shell style hand guards and since I bought free floating guards I had to have a gunsmith put the hand guards on. It required the removal of the flash hider, FSB, barrel nut etc. and I didn't have the tools to do it on my own.
When I originally got the gun back, I noticed the front A2 post looked canted. When shouldering, it was visibly tilted to the left. The gunsmith must has rushed it or whatever (he did it very quickly with me still in the store).
So, I took the gun back and he adjusted it. This time it seems *pretty* dang straight up and down when you follow the picatinny down to the FSB. I say pretty dang straight because It still could be ever so slightly to the left.
When I sighted the gun in, all 4 people I was with including myself were shooting way to the right. I wound up clicking the windage over about 13 clicks from center to 0 it in @60 yards.
Does anyone have any advice on what my issue could be? Should I take the gun back to the gunsmith a third time? I emailed him and he wants me to bring it back.
-BCM: upper receiver w/ 16" M.P./H.P. hammer forged barrel, lower receiver, bolt carrier group, "Gunfighter" Mod. 4 charging handle
-Daniel Defense 9.0" Lite free floating hand guard
-Troy Ind. Rear BUIS
-Magpul: CTR stock, MOE+ grip w/battery box, B.A.D. lever, A.S.A.P. rear sling attachment & P-Mags.
I've included some pictures for reference for you guys.
Thanks!
Steve
http://i44.photobucket.com/albums/f6/89kicker_iroc/DSC02566.jpg
http://i44.photobucket.com/albums/f6/89kicker_iroc/DSC02567.jpg
http://i44.photobucket.com/albums/f6/89kicker_iroc/2011-11-01_14-00-05_105.jpg
http://i44.photobucket.com/albums/f6/89kicker_iroc/DSC02564.jpg
http://i44.photobucket.com/albums/f6/89kicker_iroc/DSC02565.jpg
http://i44.photobucket.com/albums/f6/89kicker_iroc/DSC02533.jpg
Welcome to M4C.
I want to make sure that I am tracking here. Did this barrel already have an FSB in place, and it was simply removed in order to install the rail? If so, then I am not seeing how it can be off unless he really beat the pins in. Generally when doing an FSB removal I make sure to put the pins back in the same hole that they were removed from.
13 clicks isn't excessive and I wouldn't be concerned.
Why were trying to zero at 60 yards? I recommend that you do either a 50 yard or 100 yard zero.
Welcome to M4C.
I want to make sure that I am tracking here. Did this barrel already have an FSB in place, and it was simply removed in order to install the rail? If so, then I am not seeing how it can be off unless he really beat the pins in. Generally when doing an FSB removal I make sure to put the pins back in the same hole that they were removed from.
13 clicks isn't excessive and I wouldn't be concerned.
Why were trying to zero at 60 yards? I recommend that you do either a 50 yard or 100 yard zero.
The upper had the FSB mounted from the factory. I wanted the upper they offered with then DD guards already on, but I waited 8 months for it on backorder and then said screw it. BCM is great with emailing you back, but are terrible with giving a dang close eta on products out of stock.
I sighted at 60 because I am only a recreational shooter, and my range setup at my hunting cabin is approx 60 yards from the porch.
Since that is the factory FSB, and you only moved it 13 clicks and based on your photo then I wouldn't be concerned.
I would still sight the weapon in correctly. You can zero at 50 which will probably more than adequate for your needs.
The upper had the FSB mounted from the factory. I wanted the upper they offered with then DD guards already on, but I waited 8 months for it on backorder and then said screw it. BCM is great with emailing you back, but are terrible with giving a dang close eta on products out of stock.
I sighted at 60 because I am only a recreational shooter, and my range setup at my hunting cabin is approx 60 yards from the porch.
Since that is the factory FSB, and you only moved it 13 clicks and based on your photo then I wouldn't be concerned.
I would still sight the weapon in correctly. You can zero at 50 which will probably more than adequate for your needs.
But if it was canted dramatically when he put the guard on initally, that means it could still be somewhat canted, right?
The DD handguard has a proprietary barrel nut and as the gaurd is tightened in place, it can twist it ever so slightly. I know this for a fact because when I got the gun back for the first time it was very, very visibly offset to the left. I'm getting the same response from the other forum saying to just leave it alone and deal with it, but if it was very canted initially, how do I know its not still barely canted?
At extremely close inspection, one side of the hand guard has just a bit more mass to the one side of the FSB. It's very, very miniscule but it's there...like a push button lead pencil width. Small, but visible. I'm not sure how else to describe it.
Steve
If it was canted dramatically then it would have had to have been a factory issue. Unfortunately, since someone has already wrenched on it then DD may not address the issue.
I have removed plenty of FSB's and installed plenty of rails to include DD and never had an issue. I have never seen a properly installed DD rail "twist". What I would do is get a proper zero on the weapon and then shoot it at longer distance which is really when you will find out where you are at. Short of that you are just beating the bush.
But if it was canted dramatically when he put the guard on initally, that means it could still be somewhat canted, right?
The DD handguard has a proprietary barrel nut and as the gaurd is tightened in place, it can twist it ever so slightly. I know this for a fact because when I got the gun back for the first time it was very, very visibly offset to the left. I'm getting the same response from the other forum saying to just leave it alone and deal with it, but if it was very canted initially, how do I know its not still barely canted?
At extremely close inspection, one side of the hand guard has just a bit more mass to the one side of the FSB. It's very, very miniscule but it's there...like a push button lead pencil width. Small, but visible. I'm not sure how else to describe it.
Steve
That flip up, grabasstic excuse for a sight is more likely to be out of whack. Is that one of those Troy creations? They're ALWAYS popping up on the forums with lots of windage required.
And I agree... the windage is acceptable.. even with the poo sight.
Did you check that the FSB was perfectly straight before you had the work done on it? I have in the past received a factory BCM upper with a slightly canted FSB. It's unlikely the smith made an error reinstalling the FSB.
Another possibility is that the barrel nut may be over torqued. Did the smith remove the barrel at any point?
13 clicks is within spec. But if it really bothers you, an alternative is going with a low pro gas block and floating a midlength rail over it.
If the smith wants it back take it back. I prefer as close to zero wind in live fire as possible on my rifles for several reasons. As long as you know where you're hitting at other ranges (if you intend to shoot at other ranges) don't worry about your zero range.
I know what is wrong with your FSB, you are drinking STROH's! :jester:
Sorry, couldn't hellp myself. Off to the corner I go.
C4
I know what is wrong with your FSB, you are drinking STROH's! :jester:
Sorry, couldn't hellp myself. Off to the corner I go.
C4
That was at deer camp...my brother in law drinks it, not me lol.
By the way, I purchased the lower from you last earlier this month, lol small world
Did you check that the FSB was perfectly straight before you had the work done on it? I have in the past received a factory BCM upper with a slightly canted FSB. It's unlikely the smith made an error reinstalling the FSB.
Another possibility is that the barrel nut may be over torqued. Did the smith remove the barrel at any point?
13 clicks is within spec. But if it really bothers you, an alternative is going with a low pro gas block and floating a midlength rail over it.
No because it came without handguards from bravo and I didn't think to measure it when I first got it anyhow.
The DD rail uses a proprietary barrel nut.
Did you check that the FSB was perfectly straight before you had the work done on it? I have in the past received a factory BCM upper with a slightly canted FSB. It's unlikely the smith made an error reinstalling the FSB.
Another possibility is that the barrel nut may be over torqued. Did the smith remove the barrel at any point?
13 clicks is within spec. But if it really bothers you, an alternative is going with a low pro gas block and floating a midlength rail over it.
Since that is the factory FSB, and you only moved it 13 clicks and based on your photo then I wouldn't be concerned.
IG, how much is too much? I'm in similar shoes. My BCM upper appears to be canted slightly left. A Troy rear (which I no longer use) took 40 clicks but was still within the adjustment range. BCM (with typically awesome CS) offered to take a look for me but I'm not sure it's worth the trouble... it's my HD and farm rifle. Shots beyond 50 yds uncommon... beyond 100 unlikely. I can still hit minute-of-coyote at those ranges just fine and I otherwise love the shit out of that upper.
So for me and the OP... at what point should a cant make you stress out? If you're windage is off by "x" at 100 yards, for example?
If you are concerned about it send it in. If I think I think real hard when I BZO'd my issue M16A2 rifle, my rear sight was moved left about 9 clicks and my front sight post was down about 3.
Excessive to me would maxed out left or right and still not being able to get a good zero.
I also use a Troy front and rear sight. In this case I would put an A2 carry handle on the gun and then PROPERLY attempt to zero it.
IG, how much is too much? I'm in similar shoes. My BCM upper appears to be canted slightly left. A Troy rear (which I no longer use) took 40 clicks but was still within the adjustment range. BCM (with typically awesome CS) offered to take a look for me but I'm not sure it's worth the trouble... it's my HD and farm rifle. Shots beyond 50 yds uncommon... beyond 100 unlikely. I can still hit minute-of-coyote at those ranges just fine and I otherwise love the shit out of that upper.
So for me and the OP... at what point should a cant make you stress out? If you're windage is off by "x" at 100 yards, for example?
If you are concerned about it send it in. If I think I think real hard when I BZO'd my issue M16A2 rifle, my rear sight was moved left about 9 clicks and my front sight post was down about 3.
Excessive to me would maxed out left or right and still not being able to get a good zero.
I also use a Troy front and rear sight. In this case I would put an A2 carry handle on the gun and then PROPERLY attempt to zero it.
Gotcha, that's good advice. I guess what I getting at though is it's not the adjustment range that concerns me, but how far off the windage will be downrange from your zero. That's basically what a cant does, right? Zero at 50, then your windage is off at 100... or zero at 100, then your windage is off at 50... am I wrong?
For me, zero'd windage at 50 but 1-inch right at 100 is within my needs... no concerns for me. Just wondering what the rest of the group would consider acceptable for a HD rifle (understanding that long-range, competition, etc. are a different story).
That flip up, grabasstic excuse for a sight is more likely to be out of whack. Is that one of those Troy creations? They're ALWAYS popping up on the forums with lots of windage required.
And I agree... the windage is acceptable.. even with the poo sight.
:dirol:
IG, how much is too much?
Not IG, but excessive windage is defined in the last pages of the milspec, I'd have to go pull up my copy to get the verbiage though.
ETA:
The MIL-R-63997B (AR) Amendment 4 31JUL93 which covered the M16A2 at that time specifies that with the rear sight set +/- 5 clicks (0.5 MOA) from center all shots of a ten round group of M855, having a horizontal and vertical SD of between 3.4 and 4 inches at 600 yards, must fall into a roughly rectangular target 17.6" tall and 11.6" wide set at 100 yards.
http://www.ar15.com/content/manuals/m16a2milspec.pdf
the M4A1 JAN94 spec calls for +/- 12 clicks (0.68 MOA) with the same but at a 22" by 16" 100 yard target.
http://www.ar15.com/content/manuals/m4a1milspec.pdf
Tweak,
Based upon what you have seen thus far. Do you think that the rear sight seems to be adjusted "excessively"?
If he can get it to zero properly at 50 yards and maintain good groups at longer distances wouldn't that mean that the FSB is fine?
Not IG, but excessive windage is defined in the last pages of the milspec, I'd have to go pull up my copy to get the verbiage though.
ETA:
The MIL-R-63997B (AR) Amendment 4 31JUL93 which covered the M16A2 at that time specifies that with the rear sight set +/- 5 clicks (0.5 MOA) from center all shots of a ten round group of M855, having a horizontal and vertical SD of between 3.4 and 4 inches at 600 yards, must fall into a roughly rectangular target 17.6" tall and 11.6" wide set at 100 yards.
http://www.ar15.com/content/manuals/m16a2milspec.pdf
the M4A1 JAN94 spec calls for +/- 12 clicks (0.68 MOA) with the same but at a 22" by 16" 100 yard target.
http://www.ar15.com/content/manuals/m4a1milspec.pdf
I didn't say it was excessive, I said the milspec defined excessive since it sounded like he wants a quantitative answer.
If it was my rifle, yes, that's excessive, I adjust mine as close to zero as possible.
I didn't say that you said that. I just wanted your opinion as to what you thought.
I didn't say it was excessive, I said the milspec defined excessive since it sounded like he wants a quantitative answer.
If it was my rifle, yes, that's excessive, I adjust mine as close to zero as possible.
I found a few more posts about troy sights possibly being machined bad and causing a tilt, i'll have to take a closer look at it. My buddie at work has a few different buis that I can try too.
Eotech is still in the mail so I'm not in a super hurry to figure this out
saddlerocker
11-30-11, 21:58
After installing my new Troy Alpha rail I noticed that my BCM 16" middy FSB is canted.
I always wondered why my rear MBUS was almost all the way to the left, but everyone said its normal and its just the sight.
Now with the built in sight on the Alpha, the rear sight is dead center, and I can see the shaved FSB canted to the left under the rail.
Im not really worried about it since I shaved the FSB and it will now just act as a gas block.
But is it possible that the gas port is not lined up properly?
The rifle has always functioned fine and certainly doesnt seem under gassed. (Perfect function with Russian ammo with H buffer is good enough for me)
Im just wondering if BCM lined up the gas port, causing the cant or if the cant is causing the gas port to be slightly covered.
Gotcha, that's good advice. I guess what I getting at though is it's not the adjustment range that concerns me, but how far off the windage will be downrange from your zero. That's basically what a cant does, right? Zero at 50, then your windage is off at 100... or zero at 100, then your windage is off at 50... am I wrong?
For me, zero'd windage at 50 but 1-inch right at 100 is within my needs... no concerns for me. Just wondering what the rest of the group would consider acceptable for a HD rifle (understanding that long-range, competition, etc. are a different story).
This was the same thing I thought until I was corrected on AR15Armory.
What I was told that even if the front sight post is canted, it won't matter once the rear sight is adjusted left or right. Once they are moved over it will match it whether it 50 yards or 150 yards. It is because you are matching the rear sight to get in line with the front sight even if its way off, it wont matter. :meeting:
After installing my new Troy Alpha rail I noticed that my BCM 16" middy FSB is canted.
I always wondered why my rear MBUS was almost all the way to the left, but everyone said its normal and its just the sight.
Now with the built in sight on the Alpha, the rear sight is dead center, and I can see the shaved FSB canted to the left under the rail.
Im not really worried about it since I shaved the FSB and it will now just act as a gas block.
But is it possible that the gas port is not lined up properly?
The rifle has always functioned fine and certainly doesnt seem under gassed. (Perfect function with Russian ammo with H buffer is good enough for me)
Im just wondering if BCM lined up the gas port, causing the cant or if the cant is causing the gas port to be slightly covered.
Knowing how BCM installs and checks their FSB's, I can just about gurantee that it was set right from the factory.
Assuming you re-installed the FSB correctly, the GP will be lined up.
C4
saddlerocker
12-01-11, 12:02
Knowing how BCM installs and checks their FSB's, I can just about gurantee that it was set right from the factory.
Assuming you re-installed the FSB correctly, the GP will be lined up.
C4
Im not saying your wrong, as you clearly know more than I, but I didnt remove the FSB, I cut/shaved it while on the barrel (ghetto, I know)
And again, from day one my rear windage was almost all the way left, and now dead center with the new built in Troy front flip-up.
And while probably unrelated, the only thing keeping the handguard cap from spinning freely was the gas tube.
Both these are moot points now that the handguard cap is removed and the FSB shaved. So no need to have BCM look at it, and not sure what they would do anyhow, considering I hacked it all up.
ETA: If you are just saying the GP is most likely lined up, I agree. Im not sure if you are addressing the FSB cant or the GP alignment, or both, I may have misread.
But is it possible that the gas port is not lined up properly?
Remove the FSB and you should be able to see the scar on the barrel left from the gas port in the FSB. You can also rotate the FSB 180 and see how the gas port lines up with the hole between sling swivel bosses.
That flip up, grabasstic excuse for a sight is more likely to be out of whack. Is that one of those Troy creations? They're ALWAYS popping up on the forums with lots of windage required.
And I agree... the windage is acceptable.. even with the poo sight.
Took it off and took a close look at it, everything seems straight on it as far as the CNC'ing goes. I dont think the rear sight is the problem although it seems you have an issue with Troy...:confused:
I guess I can try to zero my eotech with the rear sight down and then flip up the sight for a comparison, right? If the rear sight is way off then I would know for sure its the BUIS vs. the FSB being canted too much.
I have a 552 and a 3x magnifier coming my way soon.
Steve0
I had this same issue a few months ago with a BCM upper. I sent it off to have a DD Lite rail installed and a muzzle break pinned(needed a gun I could take across state lines without having to notify anyone). Anyway, BCM was contacted and they agreed to look at it. I sent it in and they sent it back 2 weeks later good as new. Not saying they will do that for you, but it's worth a shot. Their customer service is outstanding and if it bothers you, it's definitely worth sending the upper in for inspection.
I had this same issue a few months ago with a BCM upper. I sent it off to have a DD Lite rail installed and a muzzle break pinned(needed a gun I could take across state lines without having to notify anyone). Anyway, BCM was contacted and they agreed to look at it. I sent it in and they sent it back 2 weeks later good as new. Not saying they will do that for you, but it's worth a shot. Their customer service is outstanding and if it bothers you, it's definitely worth sending the upper in for inspection.
How can I check and see if the barrel's FSB is crooked from the factory? The handuards are already mounted.
Steve
if you read the original post they were trying to do zero or something at 60 yards. In any case he only moved the rear sight about 12 clicks.
Myself and others have already told him he is worrying about nothing. If he is truly concerned then he should be contacting Bravo Company.
How is your zero?
Thanks IG, your input is always appreciated.
I wasn't trying to be an ass, just stating what he had already stated. I would be concerned if he had taken it out and then "attempted" to zero the weapon at say 50 yards and he couldn't get it to group.
Thanks IG, your input is always appreciated.
I wasn't trying to be an ass, just stating what he had already stated. I would be concerned if he had taken it out and then "attempted" to zero the weapon at say 50 yards and he couldn't get it to group.
The weapon grouped awesome, I'm just extremely picky with my stuff and couldn't let it go that it took 13 clicks of windage to get a 2 thousand dollar AR to zero.
When my eotech comes, I'm going to sight that in and compare my irons with the dot and will go from there. I had to order the eotech from the factory so it takes 4-6 weeks :(
ICANHITHIMMAN
12-04-11, 22:33
The weapon grouped awesome, I'm just extremely picky with my stuff and couldn't let it go that it took 13 clicks of windage to get a 2 thousand dollar AR to zero.
When my eotech comes, I'm going to sight that in and compare my irons with the dot and will go from there. I had to order the eotech from the factory so it takes 4-6 weeks :(
I been tracking along on this thread, as I had a canted FSB on an no name rifle once, good info.
As for this last coment about compairing the zero from your eotech and your iron sight. In my experience this is only going to induce more doubt in your mind. The zero's from the irons to the optic are not going to be the same.
Why did your AR cost 2000.00 dollars? Am I missing something? I think you are beating a dead horse. Not sure how many people have to tell you that you are worring about nothing. But, what the hell do I know?
The weapon grouped awesome, I'm just extremely picky with my stuff and couldn't let it go that it took 13 clicks of windage to get a 2 thousand dollar AR to zero.
When my eotech comes, I'm going to sight that in and compare my irons with the dot and will go from there. I had to order the eotech from the factory so it takes 4-6 weeks :(
Why did your AR cost 2000.00 dollars? Am I missing something? I think you are beating a dead horse. Not sure how many people have to tell you that you are worring about nothing. But, what the hell do I know?
Advice is not always good advice, so yes I am going to ask everyone on here about the canting issue, I'm not just going to take your word for it. The way you are acting in this thread is definitely going to keep me from taking anything you have to say as scripture anyhow.
Add up the parts and the gun isn't a $599 bushmaster c15 at Cabelas dude.
I did and it ain't 2000.00. Ok, it's canted. Now what? You can't go to Bravo Company because someone else has wrenched on it after the fact. So what now? Take it to the original guy who may have been the one that didn't install it right?
What remedy are you looking for that hasn't been suggested? I did if everyone here is going to chime in.
Advice is not always good advice, so yes I am going to ask everyone on here about the canting issue, I'm not just going to take your word for it. The way you are acting in this thread is definitely going to keep me from taking anything you have to say as scripture anyhow.
Add up the parts and the gun isn't a $599 bushmaster c15 at Cabelas dude.
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