Has anyone shaved down a FSB while it was still on the barrel?
I have a 16" BCM mid length with MOE furniture. When I shoulder my rifle, the fingers of my support hand tend to finger bang the hell out of my FSB. Not ideal. My natural hand position suggests that I only need an 11" handguard… perhaps 13" just for extra BUIS and light real estate (11" vs. 13" is a different debate but feel free to drop knowledge).
I have had my eye on either a TRX extreme or VTAC extreme for a little while. I see now that the Troy Alpha rail utilizes the stock barrel nut, but is otherwise very similar if you opt out of the integral front sight. Naturally, If I can avoid the purchase of more tools and also not disturb an otherwise functional system… well, it would be a big monetary win if I could just hack off the delta ring, handguard cap, shave the FSB and slide the Alpha on.
I’m pretty handy with a cut off wheel and dremel. I see people have cut off installed handguard caps and delta rings, but haven’t found a FSB chopped while installed. I figure the worst I could do is some cosmetic damage or destroy the gas tube. I can’t imagine the generated heat could do any damage, so as long as I’m careful… is this an acceptable procedure?
Edit: Found a thread where this has been done. looks like it was just the FSB and barrel… not a fully assembled upper receiver group. I think I have my answer though. Sorry for the verbose post!
There is no reason you must remove the FSB before your appointment with Dr. Dremel. I would heavily tape off the barrel around the cutting area just in case as well as the muzzle & chamber end to keep FOD out of the bore. Protect the gas tube as well. When I get around to whacking my FSB, I’ll mount it up in a barrel vise and have at it. Take your time and be patient. Just like the drawing lessons in the old car magazines used to say- “Neatness Counts”
I would probably still remove the gas tube (it only takes a punch and a hammer) and wrap sections of towel around the barrel itself with duct tape. There is no reason, other than the potential for getting sloppy and nicking the barrel, that the FSB can’t be cut down while installed.
I agree with Rob on this one. I would also suggest that covering the gas port to gas tube hole would be a good idea as well, to prevent metal and finish shavings from getting into the system.
Rob: Perhaps I’ve been brain dead, but I couldn’t figure out your newish avatar until just this moment; actually, it just looked like Rorschach. Now, I finally see it. After all, those are not windmills, but giants!
I’ve done it before on a post-ban upper with a pinned comp so removing the FSB would’ve been a PITA. In any event tape the barrel with painter’s/body shop tape (the blue or green stuff). You should have several layers of tape (the more the merrier) so that if you slip with the Dremel, the barrel has some protection before it gets any cosmetic damage. Don’t forget to tape off the little section of barrel between the pins. I took the gas tube out and plugged the holes with tape as well. Get at least one stack of cut-off wheels and two to three coarse and fine grinding wheels. Start with the cut-off wheels to lob off the big stuff, move to the coarse wheels to get the shape right and use the finer wheels to make it purty.
I have done a few still in the barrel and although it is a little more time consuming, it’s not a problem.
If using a Dremel get the heavy duty cut off discs. If I recall correctly it took one disc to cut the top portion of the FSB and another to remove the bayonet lug and other grinding. Don’t worry if it looks perfect- just make sure that you remove enough so the block fits under the rail and isn’t hitting anywhere.
Once that is done you can use the various stone attachments to slim it down more. I then use emory cloth to get the cut areas nice and smooth. I have refinished mine with black High Temp BBQ paint and Brownells Alumahyde. Both have held up.
I do advise removing the gas tube and putting some tape in areas where you could slip. It is not necessary to plug the gas port or anything. If in doubt when you’re done you simply use a compressor to blow air into the opening.
Good to know. I just did the rough work on one with an angle grinder, but didn’t want to keep installing and removing it from the bbl while I grind in the taper cuts on the side to fit the specific rail.
Glad to see someone benefited from this despite my ironic lack of search power.
I have decided that when I cough up for the rail and front BUIS I’m going to go ahead and chop the FSB with everything installed. Ill take pictures and whatnot so that others may learn from my possibly poor decision In the end it’s all for shits and grins, right? I wonder if a Fein and a good metal blade would work for this. Perhaps that would be worth some experimentation… I doubt it though.
Perhaps I will test the effectiveness of the trusty hack saw and reciprocating saw just so people can see how they work. For that matter, we have a Dynafile laying around the shop somewhere… Maybe I’ll see how awesome I can get with that thing.
I just did it to mine today, I started with it on the barrel but then decided to take it off due to the high speed of the dremel. It would sometimes take off on it’s own. Just wrap a towel around the barrel and then tape it in place. I used 5 cut off wheels, they kept breaking or just burning out, 2 coarse grinding stones and one polishing stone. Then cleaned it with degreaser and sprayed it lightly with flat black paint. I also used small drill bits to plug the holes before I sprayed it. The hand guard cap comes off easy with tin snips especially if you move the FSB an inch forward.
Came out great now just gotta test it at the range…
You can have it done QUICKLY, done INEXPENSIVELY, done CORRECTLY. Pick any two.
In reality, the Dremel is a poor choice for cutting the FSB as the cut offf wheels are too small. An angled die grinder with more torque and larger diameter cut off wheels is a much better choice, but they are pneumatic and few folks have air compressors. A reciprocating saw (like a Sawzall) would work very well, just be careful and protect everything. Clean up the cuts after with a Dremel or other die grinder
A die grinder is a “must have” tool in my box. You ever can’t get a screwdriver on a hose clamp? Die grinder. Ever need to make special size punch from a drill bit? Die grinder. Ever need to cut a notch in a 2X4 whatever that thinggy bolted to the floor is called? Die grinder. Mine is electric, a Milwaukee. And, yeah, it would make short work of a FSB though a Sawzall would also be a good candidate. The FSB I cut, I used a hacksaw. Good quality, new blade, right tooth pitch, made short work of the mild steel FSB. Smoother finish than with a Sawzall. File it a little bit, no big deal.
I’ve done maybe a dozen and the dremel is the most time consuming. 4" peanut grinder with a cut off wheel for the rough stuff, dremel for the touch up and shaping, fine sand paper for finish, degrease and paint. Obviously it’s easier if you can remove them and chuck them up in a vise first but I’ve done 2 while on the barrel. You just have to be a little more careful.
In the end it’s all for shits and grins, right? I wonder if a Fein and a good metal blade would work for this. Perhaps that would be worth some experimentation… I doubt it though.