View Full Version : gas block troubles.need help...
I just got this m4 upper off a buddy and the a2 front sitr gas block has no tapper pins and it only has a set screw holding it in place.well when i fired it the gas block blew forward. the guy said he had blue locktight on the screw holding it and it worked fine . i think it striped it out because it wont tighten at all when i try..shoukd i put red locktight in it? .thought about a quad rail gas block but i cant put magpul flip ups on that can i? What do you guys think about jt? I want to keep a magpul m.o.e handgaurd on the rifle and keep it as simple as i can
Do you mean it's a clamp-on FSB or a set-screw FSB? No taper pins? If it's a set-screw FSB, is the barrel dimpled? What happened to your gas tube when the FSB blew off the front?
No, you can't put a Magpul front site on a railed gas block. Why don't you buy another clamp-on or set-screw FSB? Or why not re-drill/re-tap the one you have?? Or better yet, buy a regular FSB and send it off to have it pinned?
AR15barrels
02-25-13, 02:03
It is common practice for front sight bases to be retained with green loctite.
You only need the setscrew to hold the sight in place while the loctite cures.
Another solution is to have a good AR gunsmith pin your FSB to the barrel.
Make sure they have a good fixture like this one to align it correctly:
http://ar15barrels.com/tech/FSB-installation.jpg
I don't know much about being a gunsmith. But i do have a lot of years with loctite using it on nuts and bolts on race car,dirt track car, motocross bikes.Loctite on new bolts and nuts work great but if you ever have to take it a part you have to really clean and get all the loctite off the threads or replace the bolt and nut.Bigger bolts and nuts are not that big of a deal getting them clean but small ones like on your fsb its really important. If any loctite is left on the threads is like sand or dirt on the threads and when you tighten down the bolts they are easy to strip. And on the small threads like on your front sight it would be really easy to strip the threads and not get a good torque on the bolt. I have buddies who have bolted on fsb and had no trouble. But pining one is the way i go.
As to Loc Tite....pretty fair amount of heat generated at the gas block and barrel. Needs to be pretty high-temp stuff.
AR15barrels
02-25-13, 11:41
As to Loc Tite....pretty fair amount of heat generated at the gas block and barrel. Needs to be pretty high-temp stuff.
Highpower match rifles have been built that way for 15+ years without problems.
Highpower match rifles have been built that way for 15+ years without problems.
No need for high temp threadlocker on AR15 barrels and gas systems then?
As to Loc Tite....pretty fair amount of heat generated at the gas block and barrel. Needs to be pretty high-temp stuff.
I have wonder about using loctite on a fsb because of the high heat area. I an not sure of how high the temps get on a fsb but i would think it would be quite high.Sometimes you have to use heat to break lose a bolt that has loctite on them.So that is why i wounder how well loctite works on fsb.
Green Loctite is made to be used on press fit parts, not threads. When used on gas-blocks, it is used where the block fits to the barrel
AR15barrels
02-25-13, 18:51
Green Loctite is made to be used on press fit parts, not threads. When used on gas-blocks, it is used where the block fits to the barrel
Correct.
Most people don't know about green or purple because all you hear about are the more common blue and red variants for thread locking...
Green is for sleeve retaining.
It does NOT need to be a press fit though.
Just a slip fit.
The green loctite fills the gap between the parts.
AR15barrels
02-25-13, 18:54
I have wonder about using loctite on a fsb because of the high heat area. I an not sure of how high the temps get on a fsb but i would think it would be quite high.Sometimes you have to use heat to break lose a bolt that has loctite on them.So that is why i wounder how well loctite works on fsb.
I would not use it to retain a machine gun FSB, but it works fine on 20" match rifles that don't get used on full auto or even at a high rate of fire.
The main reason for loctite retention of the FSB is do that you don't distort the barrel while pressing taper pins into the side of it.
If your number one requirement is accuracy, you can do a lot of small things different when assembling an AR...
I would not use it to retain a machine gun FSB, but it works fine on 20" match rifles that don't get used on full auto or even at a high rate of fire.
The main reason for loctite retention of the FSB is do that you don't distort the barrel while pressing taper pins into the side of it.
If your number one requirement is accuracy, you can do a lot of small things different when assembling an AR...
Ok that makes a lot sense. Is there even a thing call high temp loctite??
AR15barrels
02-25-13, 20:41
Is there even a thing call high temp loctite??
Yes.
The hi-temp versions are usually rated about 100 degrees higher than the standard grades.
Standard grades are good to about 350f.
Hitemp is good to about 450f.
A propane torch removes any of them.
I like rocksett for high temp applications.
I just got this m4 upper off a buddy and the a2 front sitr gas block has no tapper pins and it only has a set screw holding it in place.well when i fired it the gas block blew forward. the guy said he had blue locktight on the screw holding it and it worked fine . i think it striped it out because it wont tighten at all when i try..shoukd i put red locktight in it? .thought about a quad rail gas block but i cant put magpul flip ups on that can i? What do you guys think about jt? I want to keep a magpul m.o.e handgaurd on the rifle and keep it as simple as i can
The FSB should be pinned unless the upper is for some special use.
Well it worked for a few rounds... now the gun wont eject the shells.. it short strokes. I changed the fsb out to a low profile gas block and it still does it.. i check the gas tube its clean..what.would be my problem
AR15barrels
02-28-13, 22:39
Well it worked for a few rounds... now the gun wont eject the shells.. it short strokes. I changed the fsb out to a low profile gas block and it still does it.. i check the gas tube its clean..what.would be my problem
What ammo?
What magazines?
What buffer?
What spring?
How many rounds fired on the bolt carrier group?
How many rounds fired on the upper receiver?
What lower parts kit?
What is the gas port size in the barrel?
Read this: www.ar15barrels.com/prod/operation.shtml
Are you SURE it is short stroking from being undergassed and not failure to eject due to being overgassed?
Buffer and spring .i dont remember what.i put in the lower. i think its a rifle spring.but it.works with my other carbine uppers.. i was shooting wolf ammo. i eveb changed mags out.. how would i know if it was over gassed? Gas port size? Dont have a clue
AR15barrels
03-01-13, 01:03
i was shooting wolf ammo.
Dont have a clue
Try some good brass cased ammo.
Wolf ammo and pmc bronze are both known causes of short stroking in otherwise good guns.
I shot some brass ammo today ..it fired twice this time then i had a ftf.. would it be mine buffer spring? I took.it out..its 10.75 inchs .. i took the gun apart and made sure the barrel was tight and now itll only fire once again...i changed the gas tube,bcg and recoil buffer and spring .
If you want some SERIOUS assistance, please take the time to post coherent and complete sentences so we can help you.
I shot some brass ammo today ..it fired twice this time then i had a ftf.. would it be mine buffer spring? I took.it out..its 10.75 inchs .. i took the gun apart and made sure the barrel was tight and now itll only fire once again...i changed the gas tube,bcg and recoil buffer and spring .
Well it worked for a few rounds... now the gun wont eject the shells.. it short strokes. I changed the fsb out to a low profile gas block and it still does it.. i check the gas tube its clean..what.would be my problem
Do you have the gas block centered over the gas port properly?
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