View Full Version : FSB shaving question
Just picked up a 6920 over the weekend on sale. Kind of a knee-jerk purchase since the price was so low.
My 2 middy BCM rifles sport c4 rails, really like them. For the 6920 I was thinking of going with a 12" fortis rail, as I am not a fan of the carbine length handguards. Installation would be fairly similar to the c4 rails I did except I would need to shave the FSB.
I've watched some vids and read descriptions here, but they all show with the FSB taken off. I was wondering if it's feasible to accomplish this task leaving the FSB on the barrel.
My two concerns are not wanting to eff up the great job colt already did pinning this FSB. I also have a bad memory from unpinning the FSB on one of my bcm uppers. Those things were a PITA to remove, more so than any other FSB I've encountered. I'd rather avoid going thru that again if possible.
If I use a hacksaw on the FSB while it's attached and grind rough edges with a dremel, as long as I'm careful, what am I missing? Why the need to take off?
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No need to remove pins if you are going to use the original barrel nut. However you will need to cut off the delta ring/spring and front handguard cap. The front cap doesn't come off so easy or pretty...
Front cap not too difficult with some sheet metal clippers.
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I have had a front cap peel off after a couple cuts, and another that refused to peel that final couple mm and had to be left in place with edges cut off.
Toyoland66
12-02-13, 22:16
Just a thought but have you looked at the fsp cutout rails?
If you want to cut the fsp on the barrel wrap the barrel with towels, tape, etc to protect it in case you slip with the grinder, it is easy to do. If you are planning on a spray finish on the fsb then this is a viable option.
That being said, I just did my BCM this weekend and was able to pop the pins in 1 whack using a 2 lb drilling hammer and 1/4" punch to get them started. I did it on the concrete floor using steel plates to shim and support the FSB to ensure all of the force was transferred into the pins. Since I removed the fsb completely I was able to reparkerize it afterwards.
I shaved the FSB on my LMT with it still on the barrel, as it is a 14.5 with a perm attached FH. I did the delta ring in 2 halves (2 cuts most of the way), and then inserted a screwdriver and pried it apart, and springs with a dremel, and some pliers on the handguard cap after cutting slots to ensure I didnt get into the receiver or barrel.
Cut the FSB with a hack saw, then clamped the upper down, and did shaping with an angle grinder/cutoff wheel, cause the dremel wasnt working very well. Before I started I used a sharpie to draw on shape on the FH, then just slowly ground down to the point, then just shaped by hand.
If you are not comfortable using an angle grinder, be careful. They can get out of hand pretty quick.
Touched it up with some Birchwood and Casey Aluma Black.
On the handguard cap I usually cut it into 2-3 evenly spaced pieces. Then take a small vise grip. Lock the vise grip on one of the cut sections and it usually just peels off as I twist the vise grip.
-Jax
I shaved the FSB on my LMT with it still on the barrel, as it is a 14.5 with a perm attached FH. I did the delta ring and springs with a dremel, and some pliers to ensure I didnt get into the receiver.
Cut the FSB with a hack saw, then clamped the upper down, and did shaping with an angle grinder/cutoff wheel, cause the dremel wasnt working very well. Before I started I used a sharpie to draw on shape on the FH, then just slowly ground down to the point, then just shaped by hand.
If you are not comfortable using an angle grinder, be careful. They can get out of hand pretty quick.
Touched it up with some Birchwood and Casey Aluma Black.
This was my general gameplan minus the angle grinder. Only have the dremel to use for shaping/touch up. Why didn't the dremel work? Not enough torque?
Thanks for the replies. Not really considering carbine cutout. Want something 12-13" that uses existing barrel nut. Only mount a light and sling to rail, but desire a free floated barrel and the extended grip. If I decide to keep the FSB as is, will go with a C4 7" rail, and will just learn to live with it.
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this is much easier if you remove the FSB. hack saw or dremel to remove the triangle and then a bench grinder to shape. the time you use to R&R the FSB will be saved by not farting around with the HG cap...
mastiffhound
12-03-13, 02:13
It can be done without removal, I've done two of mine way. Do yourself a favor and remove the gas tube though. I nicked mine on the first one I did, didn't go all the way through but I didn't trust it and ordered a new one. The next one I removed before I started. Other than removing the gas tube that's it. My BCM and PSA still have a very small amount of the handguard cap left but it doesn't rattle and it's very tight. Just go slow, I've heard of people grinding right into the gas tube hole of their FSB. Take most of what you need off then see if your rail fits without touching then a little at a time until it fits.
You will also have to remove the bayonet lug, be careful. I used a high speed cut off tool from work and a my bench grinder's dremel-like grinding tool. I was unsure the first time I did it. Now it's nothing. As I said go slow, try fitting your hanguard frequently, and use high temp red permanent locktight and/or stake your screws (I did both) and you'll be good to go.
SpeedRacer
12-03-13, 08:19
It's a pain in the ass but doable. Beyond what's already been covered, I'd also suggest taping up the exposed areas of the receiver and barrel. This will help prevent knicks and also prevent metal dust from gathering in your upper. That stuff gets everywhere and is a pain to get out of all the crevices inside the upper.
This was my general gameplan minus the angle grinder. Only have the dremel to use for shaping/touch up. Why didn't the dremel work? Not enough torque?
Thanks for the replies. Not really considering carbine cutout. Want something 12-13" that uses existing barrel nut. Only mount a light and sling to rail, but desire a free floated barrel and the extended grip. If I decide to keep the FSB as is, will go with a C4 7" rail, and will just learn to live with it.
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I only have a li-ion dremel, but no, not enough torque, and it was really slow going with mine. I probably should have used my bench grinder, but the angle grinder made sense at the time, but I am pretty comfortable with it.
The tape is a good idea, as is removing the gas tube. I did that as well. for the HG cap, I used a large set of side cutters to get as close to the FSP as possible, then just worked with linemans pliers to get the metal to fatigue and break.
imho:
I'd remove all the components and mod. the FSB without anything attached. You may not want to take those FSB pins out, but the trouble to me is worth it. Large to small punches and since your cutting it up any imperfections can smoothed out/removed.
I believe the Fortis rail has a bunch of slots & you can see the FSB/barrel section under the HG, gas tube.
Some will not care for marks, or imperfections, but some will on the final appearance and if that FF HG is extremely vented/slotted than anything that would in most cases be covered up will be viewable.
* If you do end up cutting off the delta, cutting/shaving/shaping the FSB pinned on the barrel . . . Agree with removing the gas tube and I'd tape the crap out of the barrel F/R of the FSB just in case that dremel slips
fwiw/imho: Final assembly and function is key for me, as most, but I'd rather have wear from use then mods from work a rounds.
For me even if it isn't seen, its known to me, that's enough for me to take the extra time to take everything apart.
This might actually save you time, as repairs or attempts to fix marks/mistakes can lead to wasted time finding a solution/correcting.
Any coin spent is hard money earned, again imho, not worth trying when another route is available.
Plus, its easier to tape off and spray smaller components than assembled with clean lines.
fwiw: This would be different if this had a pinned/welded muzzle device and the above was not an option.
Good luck with your build & look forward to your final setup.
Have a great one
You will also have to remove the bayonet lug, be careful. I used a high speed cut off tool from work and a my bench grinder's dremel-like grinding tool. I was unsure the first time I did it. Now it's nothing. As I said go slow, try fitting your hanguard frequently, and use high temp red permanent locktight and/or stake your screws (I did both) and you'll be good to go.
Red loctite on which screws? FSB is pinned. Won't use red on rail screws since I infrequently remove when cleaning/lubing.
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imho:
I'd remove all the components and mod. the FSB without anything attached. You may not want to take those FSB pins out, but the trouble to me is worth it. Large to small punches and since your cutting it up any imperfections can smoothed out/removed.
I believe the Fortis rail has a bunch of slots & you can see the FSB/barrel section under the HG, gas tube.
Some will not care for marks, or imperfections, but some will on the final appearance and if that FF HG is extremely vented/slotted than anything that would in most cases be covered up will be viewable.
* If you do end up cutting off the delta, cutting/shaving/shaping the FSB pinned on the barrel . . . Agree with removing the gas tube and I'd tape the crap out of the barrel F/R of the FSB just in case that dremel slips
fwiw/imho: Final assembly and function is key for me, as most, but I'd rather have wear from use then mods from work a rounds.
For me even if it isn't seen, its known to me, that's enough for me to take the extra time to take everything apart.
This might actually save you time, as repairs or attempts to fix marks/mistakes can lead to wasted time finding a solution/correcting.
Any coin spent is hard money earned, again imho, not worth trying when another route is available.
Plus, its easier to tape off and spray smaller components than assembled with clean lines.
fwiw: This would be different if this had a pinned/welded muzzle device and the above was not an option.
Good luck with your build & look forward to your final setup.
Have a great one
I agree with your comments, but I was always under the impression that hammering out the pins, then knocking them back in, would in a small way degrade the strength of the pinning. Just my unscientific reasoning.
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I agree with your comments, but I was always under the impression that hammering out the pins, then knocking them back in, would in a small way degrade the strength of the pinning. Just my unscientific reasoning.
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FSB Pins Removed Properly without deforming the pins, Aligned Properly: Pretty easy as they are tapered, and Installed/Set Properly = You are GTG
fwiw: Google BCM's method of removing their pins, it's clearly written: Big to small punch
As for Red Loctite: use Blue ;) . . . . though Red does have its place if used in the right app.
- Recent M4 thread
Why you should not use red loctite...a warning.
https://www.m4carbine.net/showthread.php?143188-Why-you-should-not-use-red-loctite-a-warning&highlight=loctite
Of all the front sights I have shaved leaving on the barrel invites many chances to f it up and scratch your barrel. Do yourself a favor and remove it.
Its so easy to remove the FSB I don't see the sense in leaving it on the barrel. No chances at mistakes marking up your barrel and easier to shape the FSB once cut down when removed.
Steel head
12-04-13, 12:36
I used a cut off wheel on an angle grinder to cut the top, bayonet mount and sling mount off and shaped it with a grinding wheel and flapper wheel the used a dremel for the tight areas while it was on the barrel.
I used some leather scraps taped onto the barrel to pretext it.
Was not hard to do at all.
Just take it off. Pounding out two little pins is not hard.
Do it right, of don't do it at all.
My LMT pins are tapered, and were hardest to get out the 2nd time i took it off, but it was still easy overall.
The one time I left it on the barrel, thinking I've done this several times, I won't nick the barrel, I nicked the barrel.
Does it matter? Not really, in the grand scheme of things. It did not affect my career or marriage, it did not raise my insurance rates, it did not make me a social laughing stock among my peers, and it didn't put life nor limb in jeopardy.
But... there was a little nick in the barrel.
I remove the FSB as well. Even though the shaved gas block hides under the rail I still like it to look nicely profiled. From my limited experience I've found that kind of finish work is easier to accomplish without dinging up the barrel/tube if it is removed and I can hold it at various angles.
My LMT pins are tapered, and were hardest to get out the 2nd time i took it off, but it was still easy overall.
Wait, when did LMT start using taper pins?
Ok ok. I'll take it off. I have a bench grinder that needs some love.
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Since you and I have both had the frustrating experience of driving out BCM pins, I'll be curious to know how you think the Colt pins compare. Not bashing BCM. In fact, I prefer to know things are rock solid.
Ok ok. I'll take it off. I have a bench grinder that needs some love.
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catargadelendaest
12-14-13, 10:38
Wait, when did LMT start using taper pins?
I also want to know when.
Grip, are you sure you have an LMT factory barrel with taper pins?
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