koden
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Post by koden on Jan 3, 2012 14:02:41 GMT -8
I am fairly new to the AR platform and as such I have a question about gas leaks. I have taken my AR (with BHW 24" .264 barrel) out 3 times and have put ~125 rounds through it. I am working up loads for it and the gun will short stroke on any load that is not loaded towards the upper end of the powder charge. I have switched from an H buffer to standard with no improvement. I took the upper back to the shop that assembled it and the re-adjusted the gas block and used lock-tite this time around but I am still getting serious gas leaking from the tube and/or block. I know some leakage is normal but to me this looks a little more than what I would expect. This is after about 50 rounds. I am thinking about getting a clamp style block versus the set screw type and see if that helps any however I am thinking that it is coming out of the gas tube hole rather than between the barrel and gas block. Or am I worrying about nothing and this is normal behavior?
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Deleted
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Post by Deleted on Jan 3, 2012 14:25:48 GMT -8
Some leakage is normal. That much is not. It looks like is leaking around the gas tube and from under the gas block. It looks as though you have a gasblock that is over sized, and out of spec.
Your thoughts of going to a clamp on gas block should cure your problem. After all the carbon build up I would also replace the roll pin.
Also just to make sure, check that the gas tube is installed right side up.
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koden
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Post by koden on Jan 3, 2012 15:09:42 GMT -8
Thanks for the feedback. The gas tube has a bend in it so I assume it will only install one way unless the shop did the bending their self. I'll buy a new gas tube and replace it as well.
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koden
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Post by koden on Jan 3, 2012 15:16:48 GMT -8
Here is a pic of the whole setup. Any recommendation as to which low pro gas block to get? Needs to fit under a troy rail. Should I get an adjustable block?
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Deleted
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Post by Deleted on Jan 3, 2012 15:44:55 GMT -8
Hold on! I have those rails too and where you have the bottom rail there to support your bi-pod you might have a problem even with a troy that is probably the smallest of all. A clamp on is always a good idea regardless if there is leak or not. If you want I can check it out before you buy it by moving my bottom rail forward but I believe that there is no room so the solution might be to install the rail a couple of inches back. you can always get an extension. Firs let me know the section of your barrel on the gas block, it looks wider than .750" Let me know.
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koden
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Post by koden on Jan 3, 2012 17:12:53 GMT -8
Wow, good call 1shot. This is the add on rail repositioned to the rear. You can see where it was actually pushing against the rear set screw (it has a shinny edge on the set screw). I hope this accounts for the disappointing groupings I have been getting. You think it is causing the block to leak though?
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Deleted
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Post by Deleted on Jan 3, 2012 17:33:54 GMT -8
No prob. That is what I was afraid of. The leak has nothing to do with that. That rail is awesome but that nice slim profile makes it challenging with bull barrels and some gas blocks. 2 things: A) If you want to maximize accuracy potential you do not want a set screw gas block anyway but before you buy a clamp on you need to make sure. What is your barrel section? B) You do not want anything touching anything!. It is a free float for a reason. That could well affect the harmonics with inconsistent results. Think of the barrel like a piano string, you want always the same tune. hopefully a high note that it translates to more accuracy nodes. Normally with a long barrel this is even more critical so nothing in the handguard touches anything in the barrel.
Once you are done with these most basic things then you work on the loads. Long barrels can be more picky but when you hit a node the can be extremely accurate.
Tell me the section and I will let you know if the troy will work or not. Do you have a .750 block or bigger? Thanks.
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koden
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Post by koden on Jan 3, 2012 17:45:35 GMT -8
Makes sense 1shot.
The barrel is .936 at the gas block. It is one heavy rifle, especially with 25 rounds loaded.
;D
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Deleted
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Post by Deleted on Jan 3, 2012 17:54:45 GMT -8
Ok. Going downstairs with the calipers...
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Deleted
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Post by Deleted on Jan 3, 2012 18:17:16 GMT -8
No prob. That is what I was afraid of. The leak has nothing to do with that. That rail is awesome but that nice slim profile makes it challenging with bull barrels and some gas blocks. 2 things: A) If you want to maximize accuracy potential you do not want a set screw gas block anyway but before you buy a clamp on you need to make sure. What is your barrel section?B) You do not want anything touching anything!. It is a free float for a reason. That could well affect the harmonics with inconsistent results. Think of the barrel like a piano string, you want always the same tune. hopefully a high note that it translates to more accuracy nodes. Normally with a long barrel this is even more critical so nothing in the handguard touches anything in the barrel. Once you are done with these most basic things then you work on the loads. Long barrels can be more picky but when you hit a node the can be extremely accurate. Tell me the section and I will let you know if the troy will work or not. Do you have a .750 block or bigger? Thanks. That came from Whitley. I am calling BS. I can tell you from experience a set screw gas block does not effect accuracy any more than a clamp on does. Think about this, as the bullet travels up the bore it comes to the clamp on gas block. It meets the same resistance every time in exactly the same place. ( In theory the barrel swells as the bullet travels up the bore. It also re tracks back to its original shape after the bullet has passed. ) The same goes for a set screw system they are exactly the same. His other theory about compressing the wall of the barrel is just that, a theory. If you can show me how you can compress a minimum of 3/8 of an inch of steal with a #10 cap screw tightened as on a gas block I will eat crow.
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Deleted
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Post by Deleted on Jan 3, 2012 18:34:40 GMT -8
Whitley is not the only one. He got it from many other high power competitions and long range gurus. He is not the only or the first one. One does not spend lots of money on a system and then bolts anything to it. I do not know anyone that does that but I see others do it. A metal is a malleable and flexible material. The clamp helps in several ways. But to everyone each own. I am glad the setscrew works for you. I am happy the way mine work.
Anyway, there is no luck for the OP. I measured and that rail is maxed out with the vltor. Any other the YMH or the Sadlak is not good. you need 1.7"+ to clear and only have 1.4" with the clamp screws so it is an amazing rail but not the best to go bull and then over the gas block.
Sorry to disturb here. I am happy if I can help.
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koden
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Posts: 30
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Post by koden on Jan 3, 2012 18:44:00 GMT -8
So no clamp on will work with the Troy rail and my .936 barrel.
The gas block I have is a Troy. What brand should I use to replace it?
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Deleted
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Post by Deleted on Jan 3, 2012 19:04:30 GMT -8
Here are some that will work, They are from Midway you can probably find them cheaper some where else.
DPMS SASS Low Profile Gas Block AR-15 Bull Barrel .936" Inside Diameter Steel Matte Product #: 274547 Status: Available 5.0 stars (2) Reviews $99.99
PRI Low Profile Gas Block AR-15 Bull Barrel .936" Inside Diameter Steel Matte Product #: 715693 Status: Available 4.5 stars (4) Reviews $59.99
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koden
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Posts: 30
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Post by koden on Jan 3, 2012 20:15:21 GMT -8
How close to .936 should the barrel be? I slipped the gas block down and measured the diameter under the block. The diameter measures .9335 on my calipers.
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Deleted
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Post by Deleted on Jan 3, 2012 20:42:11 GMT -8
The problem is from top to bottom. Measure from the top of the block to the bottom. The clamp type will add too much and the troy TRX rail will not work. It is a nice slim set up but not really ideal for bull type but you can fix this. I would now try to fix the one you have. eventually some leaking might stop with the own powder residue. also you can use a bit of high temperature sealant like the one used in gaskets but you need a minimum amount, almost like painting and away from the port. That will stop the bleeding right away. Also you should look for accuracy after you relocated the gas block. When debugging issues you need to go one thing at the time so you know what might be making a difference and what not. Also regarding the brake what do you have there. Some brakes, even expensive ones do more harm than good in terms of accuracy.
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