View Full Version : Is this normal??????!!!!!!
I got a brand new BCM BFH 16" middy in the mail and my Centurion C4 rail in the mail and installed that day. The FSB seemed to be a little canted to the left if looking down the rifle so I re installed the FSB. It seemed like it again. I played with it a bit and came to the conclusion that no matter what I did it always came to this position. It is VERY slight. Is my new rail an irregular or something? I am lost. Pic is below.
http://i1237.photobucket.com/albums/ff469/clj94104/4f873a5c.jpg
Whenever you remove an FSB this can happen. This is why it should only be done by qualified personnel. If I were you I would go and shoot it first.
Alright. I am going to the range tomorrow to zero the optic. It doesn't really effect too much, because I use optics but I would like the option of BUIS down the road. If it is in fact canted slightly can this cause other issues? Looking through the magnifier the reticle on the EOTech is stationary, and the front sight post is centered underneath it perfectly.
It is possible its an illusion?
Barrel alignment seems okay. Do you guys concur?
http://i1237.photobucket.com/albums/ff469/clj94104/159cffd6.jpg
Just came across this thread. https://www.m4carbine.net/showthread.php?t=18088 Grant says hitting the FSB wa rubber mallet may solve my slight misalignment issue. Do you gentlemen agree?
polymorpheous
05-01-12, 01:10
Just came across this thread. https://www.m4carbine.net/showthread.php?t=18088 Grant says hitting the FSB wa rubber mallet may solve my slight misalignment issue. Do you gentlemen agree?
Please attempt to zero your weapon before hitting it with a hammer.
Please attempt to zero your weapon before hitting it with a hammer.
Eh, I kinda want to see what happens when it gets hit with a hammer.....
Will do.dont have any irons to try and zero with, and I don't think zeroing the optic will be an issue so to be continued I guess. I will zero the optic tomorrow and let you guys know how it goes.
Um....how does the top rail of the handguard align with the rail of the upper receiver?
If that's off, then that means your handguard is the culprit.
If that isn't off, use your calibrated eyeball to see if the rail bends or twists the further it goes out from the reciever towards the front sight.
If it doesn't, then you are correct that your FSB/barrel (most likely the entire barrel) is slightly canted.
If it is the FSB and not the entire barrel, It probably relates (as I-Gunz noted) to your install of the FSB. How far in have you driven the FSB pins?
I'll re-state, do NOT start smacking the shit out of your rifle until you have gone through the above checks and then, all of that being good, taken the damn thing to the range and shot it first.
p.s. did you re-torque on your barel nut during the install process?
Did you use something to bridge the rail (like a carry handle) before tightening down the rail bolts?
To check if fsb is canted, take everything off (i.e rail, optics) eyeball down the upper rail at the FSB. You can get an idea if FSB is straight.
If the FSB is in fact canted, and it really bothers you... Install a low pro gas block and get an 11" rail to float right over. This way you can install flip up back up irons and have a clean sight picture when using optics.
Inkslinger
05-01-12, 06:12
It looks like the rail is a little off. Look how the optic and the FSB line up, then look at the rail. The rail looks turned slightly to the right.
polymorpheous
05-01-12, 07:03
Did you use something to bridge the rail (like a carry handle) before tightening down the rail bolts?
To check if fsb is canted, take everything off (i.e rail, optics) eyeball down the upper rail at the FSB. You can get an idea if FSB is straight.
If the FSB is in fact canted, and it really bothers you... Install a low pro gas block and get an 11" rail to float right over. This way you can install flip up back up irons and have a clean sight picture when using optics.
Or if it impedes function, the OP could send it back to the manufacturer.
FSB > flip up BUIS
FSB > flip up BUIS
X2... No reason not to have one unless its a precision build
Just came across this thread. https://www.m4carbine.net/showthread.php?t=18088 Grant says hitting the FSB wa rubber mallet may solve my slight misalignment issue. Do you gentlemen agree?
LOL. First, shoot the gun and verify what is going on. Then, it if it too far out, have the FSB re-installed by someone that knows what they are doing.
C4
I have not re torqued the barrel nut. All I did was cut off the delta ring, spring, etc, and then removed the FSB pins and slid the FSB forward just slightly to cut off hand guard cap. Then slid it back into place and knocked the pins in all the way. I just re-aligned the rail (it was a little bit off to the right, I used the carry handle as a bridge during install and its perfect now) and the FSB still seems SLIGHTLY canted left. I tried to go to the range this morning but they're closed, gotta wait until tomorrow. Hopefully it doesn't impair function (I don't think it will)
I have not re torqued the barrel nut. All I did was cut off the delta ring, spring, etc, and then removed the FSB pins and slid the FSB forward just slightly to cut off hand guard cap. Then slid it back into place and knocked the pins in all the way. I just re-aligned the rail (it was a little bit off to the right, I used the carry handle as a bridge during install and its perfect now) and the FSB still seems SLIGHTLY canted left. I tried to go to the range this morning but they're closed, gotta wait until tomorrow. Hopefully it doesn't impair function (I don't think it will)
I have never installed this rail (yet), but isn't one of the things going for it is that you do NOT have remove the FSB???
C4
polymorpheous
05-01-12, 10:17
I have never installed this rail (yet), but isn't one of the things going for it is that you do NOT have remove the FSB???
C4
Correct.
The FSB does not have to come off to install this rail.
Correct.
The FSB does not have to come off to install this rail.
Thought so. Since the FSB can be a PITA to remove and to re-install properly (as the OP found out), why remove it if the rail doesn't require it???
If one was going to go through all this trouble, then why not buy a one piece, free floating rail???????
C4
Will do.dont have any irons to try and zero with,
That'll make this more difficult.
That'll make this more difficult.
I take that back as I did find my carry handle buried in the safe. It has iron sights.
I may say screw the FSB. It's a nice option, but I'm growing tired of this issue quickly. If it functions properly I may leave it be. You can hardly tell its canted.
Had it inspected by local class 3 dealer that does smithing and machining. The cast frame for the sight post isnt true (very minor imperfection) but the sight post is aligned properly. I may cut it down into a pinned gas block and install a flip up front sight eventually but it is good for now. Taking to the range tomorrow.
polymorpheous
05-01-12, 18:37
You are making way too big of an issue about something that in all likelihood is not an issue.
Suwannee Tim
05-01-12, 19:48
So we've decided that a canted front sight while maybe not normal is not a disaster. What I want to know, is six question marks and six exclamation marks normal?????!!!!!!
So we've decided that a canted front sight while maybe not normal is not a disaster. What I want to know, is six question marks and six exclamation marks normal?????!!!!!!
No but it does get people's attention. :D
I take that back
Shoot it.
If you didn't mess with the barrel nut then, at worst, the handguard is canted.
mkmckinley
05-01-12, 21:40
Just out of curiosity, whats the proper way to reinstall a pinned FSB without canting it? I'f done it a dozen time or so and never had a problem but I've never had any formal instruction. Don't the pins pretty much recenter the FSB when you pound them in?
polymorpheous
05-01-12, 21:58
Just out of curiosity, whats the proper way to reinstall a pinned FSB without canting it? I'f done it a dozen time or so and never had a problem but I've never had any formal instruction. Don't the pins pretty much recenter the FSB when you pound them in?
Yup.
Just pound the pins all the way in.
Don't the pins pretty much recenter the FSB when you pound them in?
Pretty much exactly.
Weapon shoots perfectly. Went to the range today.
Just out of curiosity, whats the proper way to reinstall a pinned FSB without canting it? I'f done it a dozen time or so and never had a problem but I've never had any formal instruction. Don't the pins pretty much recenter the FSB when you pound them in?
Yes, but many people do NOT pound them in all the way. This directly impacts where the FSB lines up.
C4
Suwannee Tim
05-02-12, 20:03
I was pretty amazed how hard you have to hit taper pins to get them seated. I can't remember any exposure to taper pins prior to the AR but I've had plenty of experience with dowel pins and you don't have to hit them nearly so hard to make them move.
Thought so. Since the FSB can be a PITA to remove and to re-install properly (as the OP found out), why remove it if the rail doesn't require it???
If one was going to go through all this trouble, then why not buy a one piece, free floating rail???????
C4
I watched a short video on installing the Centurion where the FSB was removed to cut off the handguard cap. Is there a recommended method to remove the handguard without removing the FSB?
I think they exhibit the 'taper lock' phenomena, much like a drill chuck for a lathe. A machinist I knew awhile back explained to me how those taper locks work. He said anything with a taper greater than 0 but less than about 7.5 degrees would exhibit that locking characteristic.
I was pretty amazed how hard you have to hit taper pins to get them seated. I can't remember any exposure to taper pins prior to the AR but I've had plenty of experience with dowel pins and you don't have to hit them nearly so hard to make them move.
motorolahamm
05-03-12, 07:38
NO irons Really no IRONS :D, i would get a good set of BUIS sights before moving to a optic incase it fails you have a fall back,
I watched a short video on installing the Centurion where the FSB was removed to cut off the handguard cap. Is there a recommended method to remove the handguard without removing the FSB?
Are we talking about the the HG cap? I would just remove the gas tube (will give you more play) and then take some tin snips (or something like that) and cut it off. If you are the dremel "master" you could use a cut off wheel. When you get close STOP cut if off the rest of the way with a hand tool.
C4
Are we talking about the the HG cap? I would just remove the gas tube (will give you more play) and then take some tin snips (or something like that) and cut it off. If you are the dremel "master" you could use a cut off wheel. When you get close STOP cut if off the rest of the way with a hand tool.
C4
Yes, sorry. I didn't catch my grammar error, I meant the HG cap.
NO irons Really no IRONS :D, i would get a good set of BUIS sights before moving to a optic incase it fails you have a fall back,
Yeah I did find my carry handle, but I will never use it. I will probably get a set of Troy BUIS for the rear. I just need to make sure it will fit under my magnifier on the flip to side mount. I think the Troy will. I must say, I went from a Bushmaster 14.5" carbine to a BCM BFH 16" middy and WOW. I am happy I did that. It runs so much smoother. The front sight post lines up properly, but I think the actual frame for the sight post isn't true. No big deal. I am very happy with this rifle. The hand guard is awesome. I ran it hard at the range yesterday, couldn't feel any heat.
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