View Full Version : To chop the FSP or not!?
doubled561
11-03-13, 14:11
I'm having a heavy debate as to whether or not I should chop my FSP and make it a low pro block or not. By doing so I could expand my handguard options drastically. Anyone with any experience with the procedure want to chime in and give me your opinion, it would be greatly appreciated.
Pretty straightforward process with good results. You can cut the delta ring/nut and the handguard stop off with a dremel. Obviously should be done only if you're sure you don't ever want to go back to an FSB. Two advantages are that you won't have big open taper pin holes in your barrel and you won't have to pay anyone to pin your new $60 low profile gas block.
There are a number of youtube videos on the process, and at least on Brownell's video.
I've done it a bunch and it's worked very well. No problems and I like that the FSB is secured using two pins.
If you're going to cover the block with a handguard, pinning is no advantage. Thread-locked set-screws will hold for the life of the barrel. I would not take pinability into account in this decision.
In my opinion, once you chop the original sight base, the weapon should be considered optic-only. Irons will work in a pinch, but aluminum handguards don't provide a stable enough platform to be relying on mounted irons for marksmanship. Floated handguard flex independent of the barrel- that's why we use them. This also creates a deviance between point-of-impact and point-of-aim, using rail-mounted sights.
I've chopped, I've also opted to save the original and use a different low-profile gas block- depends entirely on my plans for the rifle.
I've had even thread locked screws come loose. Not often, but it happens. Pinning with a tapered pin SEEMS (I have no hard data here) more secure.
I have no experience with it, but I've read too many accounts on this site of set-screw gas blocks coming loose under the handguard, even with thread locker. I would opt for something pinned in place, whether it's covered or not.
PatrioticDisorder
11-03-13, 16:09
What purpose does the rifle serve? If it's more of an HD/CQB rifle with a red dot then IMO I wouldn't chop the FSB, but if you're running a low power variable, by all means chop it.
If you're just looking for more real estate, check out the DD rails or if that isn't your cup of tea, Troy rails I know they have a couple compatible with a FSB.
If you're going to cover the block with a handguard, pinning is no advantage. Thread-locked set-screws will hold for the life of the barrel. I would not take pinability into account in this decision.
Well, that's one opinion. I saw a set screw-only gas block come loose and foil the gas system. For optimal reliability on a rifle, pinning the gas block is preferable
In my opinion, once you chop the original sight base, the weapon should be considered optic-only. Irons will work in a pinch, but aluminum handguards don't provide a stable enough platform to be relying on mounted irons for marksmanship.
I don't know. My irons on my free-float hand guards are as accurate as the RDS on those rifles, which is all the accuracy I need on my carbines, but if we're putting optics on the rifle we need irons at most for back up and some would argue that even that is unnecessary. If we're putting an optic on, IMHO, an FSB becomes superfluous.
TacticalSledgehammer
11-03-13, 16:47
Cut and trim up the FSB. It's pretty easy. If you have a BCM, rustoleum's 5000 degree black engine paint matches their original finish nicely.
There's a lot of people with low pro blocks and rail mounted sights that will disagree with you.
If you're going to cover the block with a handguard, pinning is no advantage. Thread-locked set-screws will hold for the life of the barrel. I would not take pinability into account in this decision.
In my opinion, once you chop the original sight base, the weapon should be considered optic-only. Irons will work in a pinch, but aluminum handguards don't provide a stable enough platform to be relying on mounted irons for marksmanship. Floated handguard flex independent of the barrel- that's why we use them. This also creates a deviance between point-of-impact and point-of-aim, using rail-mounted sights.
I've chopped, I've also opted to save the original and use a different low-profile gas block- depends entirely on my plans for the rifle.
lethal dose
11-03-13, 18:03
There's a lot of people with low pro blocks and rail mounted sights that will disagree with you.
I'm one of them.
Why doesn't anyone mount their Aimpoint on the handguard?
I'm on the cut and paint club for this one. I have a few carbine length barrels that I wish I had purchased with FSBs - set screws with loctite and dimples still doesn't offer the physical barrier to loosening that a pinned FSB does. Set screws are a method that works for several but for me I prefer the pinned if I'm counting on it.
Archer1440
11-03-13, 19:00
Why doesn't anyone mount their Aimpoint on the handguard?
Re-read post #4 in this thread, answers your question very well.
I tried shaving a standard fsb once. It cracked on the bottom when I put the taper pins back in because I removed too much material. I ended up having a new low pro pinned on by ADCO. I personally will never try it again, but it was probably my own fault that it happened. Since then I have become more fond of a 9" rail on a mid length with a standard fsb anyways. Plenty of room for me to mount my stuff and grasp the hand guard.
No reason not to do it.
I did mine. Very easy. Just requires common sense.
Steel head
11-03-13, 19:57
I cut mine down on my AR, cut it with a cut off wheel and shaped with a grinder and dremel and painted it with high temp paint.
Was pretty easy and doesn't look bad.
TacticalSledgehammer
11-03-13, 20:09
I cut mine down on my AR, cut it with a cut off wheel and shaped with a grinder and dremel and painted it with high temp paint.
Was pretty easy and doesn't look bad.
Same here. If I lose my dremel skills and screw up the FSB, I'll then buy a low profile gas block. I'm cheap I guess.
I cut mine down on my AR, cut it with a cut off wheel and shaped with a grinder and dremel and painted it with high temp paint.
Was pretty easy and doesn't look bad.
Same for me. Sounds harder than it looks.18715
I put a C4 rail on so I didn't need to contour the bottom. I Just cut the bayo lug and sling mount
It's not that bad to do your own shaved FSB. But, it comes out looking really good using a mill, minor grind and polish, glass bead, and repark it. Unfortunately, most guys at home don't have access to that stuff. A lot of smiths won't set up the mill, unless they're doing a run of a few at least.
I did a run of a few batches to make copies of Costa 11.5" KAC uppers before you could buy them from Knights. Used what's now legacy KAC uppers with Colt 11.5" Commando barrels with the shaved FSB.
I'm pretty sure Marvin still does quality shaved FSB, his turn around isn't too bad.
+100 on pinned vs set screws. I've been the unlucky SOB at a class that was shooting under a vehicle port side down when a casing bounced back in backwards over the bolt. It hooked onto the key and made a mangled jam that pushed the gas block forward. Would've been more embarrassing if I didn't bring a backup AR.
Why doesn't anyone mount their Aimpoint on the handguard?
In my experience, field of view sucks when it is mounted that far forward.
When the screwed gas block is done correct (degrease the parts, dimple barrel, correct screws and Loc-tite) then it will hold it just fine. I have thousands of rounds through two different uppers like this and I know plenty of others who have as well.
If it's a real concern get one of the gas blocks from Clint at Black River Tactical or reach out to K.L Davis who is working with someone that makes a block that only requires drilling the hole.
mastiffhound
11-03-13, 23:48
I've done it on 2 so far. Both are rock solid, and my short time here has convinced me it was preferable to screws. I just did my 20" last month. If you have a pinned 14.5" barrel then it's the cheapest or possibly best option if you want a FF handguard as long as the new rail works with the original barrel nut. Both my rails covered them completely and you can't tell I even chopped them. As long as your handy with tools in general you can do it. Just go slow and plan out how you will do it.
It's was scary for me to tell the truth the first time I did it, I felt a little sick chopping a perfectly good part off of my AR. After I installed the new handguard it went away. I'm used to looking at firearms in general as a treasure or heirloom like Dad and Grandpa did, not that they didn't get used. They got babied though. Being on here has changed my outlook a little, they don't get babied but I'm not torture testing them either. ARs are tools, and just like my Matco ratchet they get cleaned, wiped down, and put back in place when I'm done with them.
One more thing, remove the gas tube before you cut the FSB. I didn't on the first one and nicked it pretty good with my cut off tool. I was worried that one good string of fire would make it pop. It still functioned fine but I replaced it ASAP:D
In my experience, field of view sucks when it is mounted that far forward.
Do you shoot with both eyes open?
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