View Full Version : Newb gas block question
first time tinkering on an upper, installing a free float on my spikes m4 le style upper which the fsb pins were so tight I broke my starter pins until my air hammer got them moving easily, my deal is im installing a low pro Troy gas block in its place/screw on from what I've read you should dimple the barrel for the screws, however I noticed the screws will go where the notches are cut for the a2 fsp, so do I just loctite and run the screws into those notches using them as my dimples? Also if I wanted to revert back to the a2 at some point won't the gas block screws mess up the notches?
Thanks in advance.
If it were me, I'd save a little money (return the Troy) and keep the stock FSB. Then cut it down, check for clearance, cold blue it, and it will be hidden under the rail. Pretty much bombproof.
I was thinking about doing that originally but wanted to
Save the parts and option to easily go back to an m4 carbine look if I wanted, am I opening myself up to possible reliability issues by doing this on a barrel that originally had an a2 fsp?
If there was a chance you'll go back to stock, don't muck up the pin slots. Maybe try a clamp style gas block instead of set screws. Still though, if this is going to be a fighting gun, I'd strongly suggest that it be pinned OR do what I prefer and keep the FSB intact. Simple, strong, reliable.
Guess I'm at a cross roads then, wonder what most guys do in this case aside from grinding the a2,seems to be a very common thing to replace it with a set screw low profile
I would cut down the original FSB and reinstall with the taper pins. Trying to use the set screws where the pin holes ate is going to do nothing but cause you heart ache. If the metal is thin enough, it will collapse as the set screw tightens down.
Clamp on gas blocks are larger and may give you fitment problems with you free float tube. They also place strain on the clamping screws which can lead to the screws failing
Ok so then in my situation since there was notches from an a2 grinding one down is the best way, next question, from what ive read no 2 fsb pin locations are the same? So I can't just buy a spare one to grind down and reinstall in the original notches and keep the old on intact?
Nope. They are unique and IMO would be cost prohibitive to retrofit a new one. Up to you though.
If you think you really are going to restore the barrel to the original configuration after grinding down the FSB, buy a replacement barrel
556BlackRifle
03-07-17, 09:35
There's a pretty high likelihood that you'll never go back to using the FSB on that barrel. There are a lot of guys on M4C that have cut them down and are very happy with the results. Personally I've just replaced the FSB with a low pro block - but I've never gone back to using the FSB again. (I have several FSB sitting in my parts bin.) Bottom line, next time I'll cut and grind.
Ok so I'm pretty much sol with that barrel and reverting back if i wanted, just on the fence if I wanna give up the m4 look, gonna be putting an omega x rail on it and it's a carbine gs, to bad I didn't get an omega fsp, also have a lite rail I plan to put on a bcm bfh in the future so wasn't sure how I'd like them being so similar when all set and done, would you guys even bother free floating a 16' spikes carbine length m4 style upper?
No. I wouldn't even own one!
It's up to you. If it was a Spikes FN 4150 CMV HPT MPI variety, and I had the parts on hand to float it, I probably would.
It's up to you. If it was a Spikes FN 4150 CMV HPT MPI variety, and I had the parts on hand to float it, I probably would.
I don't think It's an fn I'll have to double check, think it's just hpt mpi cl m4 profile
556BlackRifle
03-07-17, 19:14
Ok so I'm pretty much sol with that barrel and reverting back if i wanted, just on the fence if I wanna give up the m4 look, gonna be putting an omega x rail on it and it's a carbine gs, to bad I didn't get an omega fsp, also have a lite rail I plan to put on a bcm bfh in the future so wasn't sure how I'd like them being so similar when all set and done, would you guys even bother free floating a 16' spikes carbine length m4 style upper?
Actually - you can go back. It's only a problem if the pin-bores are damaged or the barrel is deformed. But in all likelihood you won't want to.
Actually - you can go back. It's only a problem if the pin-bores are damaged or the barrel is deformed. But in all likelihood you won't want to.
Won't running the set screws into the notches ruin them in general? Not sure if a clamp on will fit inside an omega
If you are set on your quest, it shouldn't be an issue if done competently. This is a Colt 16" 6920 barrel I got from a member here several years back. As you can see, I dimpled it in the other set screw location as opposed to directly under the port. Since I knew the jig was legit and checked everything I knew it was a non-issue.
http://i152.photobucket.com/albums/s188/iraqgunz/Barrel%20Dimple_zpsvr1dmcgg.jpg (http://s152.photobucket.com/user/iraqgunz/media/Barrel%20Dimple_zpsvr1dmcgg.jpg.html)
556BlackRifle
03-08-17, 00:37
If you are set on your quest, it shouldn't be an issue if done competently. This is a Colt 16" 6920 barrel I got from a member here several years back. As you can see, I dimpled it in the other set screw location as opposed to directly under the port. Since I knew the jig was legit and checked everything I knew it was a non-issue.
Won't running the set screws into the notches ruin them in general? Not sure if a clamp on will fit inside an omega
There's your answer above.
Ok I think that's what I'll try, I don't have a jig but I imagine I could just double check everything and it doesn't look like Just running the rear screw down without dimpling it will hurt anything, awesome, thanks a bunch guys.
Using the dimples is great but not necessary, if it is not a duty or combat weapon I wouldn't worry about it. If you are concerned you can always take it to a gunsmith to dimple it for you, or if you have a good drill press and vice do it yourself.
Dimples are the minimum. IMO, for duty or combat, it should be PINNED.
Using the dimples is great but not necessary, if it is not a duty or combat weapon I wouldn't worry about it. If you are concerned you can always take it to a gunsmith to dimple it for you, or if you have a good drill press and vice do it yourself.
Dimples are the minimum. IMO, for duty or combat, it should be PINNED.
Completely agree, that is why i said if it is not a duty or combat weapon for the OP it is not critical. No exceptions for combat or duty IMO.
I think I will just dimple the front hole like one poster mentioned then use high strength/temp Loctite, that should be reliable enough for combat use and wouldn't hurt anything if I ever wanted to revert back to a fsp i assume?
I think I will just dimple the front hole like one poster mentioned then use high strength/temp Loctite, that should be reliable enough for combat use and wouldn't hurt anything if I ever wanted to revert back to a fsp i assume?
You should be fine. Good luck
Get the jig if you want it done right.
Ok I think that's what I'll try, I don't have a jig but I imagine I could just double check everything and it doesn't look like Just running the rear screw down without dimpling it will hurt anything, awesome, thanks a bunch guys.
Actually it is. Please don't spread trash information here. There are plenty of other Bubba Gun Sites.
Using the dimples is great but not necessary, if it is not a duty or combat weapon I wouldn't worry about it. If you are concerned you can always take it to a gunsmith to dimple it for you, or if you have a good drill press and vice do it yourself.
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