Over gassed AR pistol

KnotRight

KnotRight

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I changed out a 223 barrel from 7.5 to 10.5" and installed an adjustable gas block. While at the range today trying to tune the block, it was completely over gassed even with the block 99% of the way closed. The brass was ejecting at 2:00. All this is with a can on the end of the gun.
Without the can, I could get the brass to eject at the 3:30 position.
When I got this gas block, it had a small round steel rod about 1/8". I am not sure what that is for. Any ideas?
 
Tim said:
What brand block?
Click to expand...
I am not sure. I thought that I ordered it from either Midway or Brownell's but my order history does not show any blocks.

Here is a picture of the pin that came with the block
Pin.jpg
 
KnotRight said:
I changed out a 223 barrel from 7.5 to 10.5" and installed an adjustable gas block. While at the range today trying to tune the block, it was completely over gassed even with the block 99% of the way closed. The brass was ejecting at 2:00. All this is with a can on the end of the gun.
Without the can, I could get the brass to eject at the 3:30 position.
When I got this gas block, it had a small round steel rod about 1/8". I am not sure what that is for. Any ideas?
Click to expand...

That’s for pinning the block. Not necessary but some barrels have predrilled holes for them and others have jigs to drill them.

I keep an old block that I use as a dimpling jig for set screws if the barrel has only one or none from the factory. I do it on my drill press but never done the complete pass through for pinning the block. If I had an M16A1, I’d probably pin it

Picture borrowed from Google images
MAbNAlS.png



What brand of barrel are you using? If it’s a common one, the port size might be available online. Might be a perfect time for an adjustable gas block. I like superlative bleed off blocks; they allow excess gas beyond your tuned setting to vent out the front of the block reducing fouling/carbon buildup, pressure, blowback, felt recoil, and temperature

And yes, they’re worth the cost especially suppressed. I run adjustable gas on ALL my semi autos
suparms.com

.750" Adjustable Gas Block, Bleed Off - Solid, Set Screw - Melonite Finish

SKU # SABO-DI-750SM The Superlative Arms Patented “Bleed Off”, direct impingement, gas block for the AR-15/AR-10/LR-308 platform adjusts the gas flow by bleeding the gas out of the front of the block instead of restricting the flow like conventional adjustable blocks. Results: The pressure used...
suparms.com
 
11B CIB said:
That’s for pinning the block. Not necessary but some barrels have predrilled holes for them and others have jigs to drill them.

I keep an old block that I use as a dimpling jig for set screws if the barrel has only one or none from the factory. I do it on my drill press but never done the complete pass through for pinning the block. If I had an M16A1, I’d probably pin it

Picture borrowed from Google images
MAbNAlS.png



What brand of barrel are you using? If it’s a common one, the port size might be available online. Might be a perfect time for an adjustable gas block. I like superlative bleed off blocks; they allow excess gas beyond your tuned setting to vent out the front of the block reducing fouling/carbon buildup, pressure, blowback, felt recoil, and temperature

And yes, they’re worth the cost especially suppressed. I run adjustable gas on ALL my semi autos
suparms.com

.750" Adjustable Gas Block, Bleed Off - Solid, Set Screw - Melonite Finish

SKU # SABO-DI-750SM The Superlative Arms Patented “Bleed Off”, direct impingement, gas block for the AR-15/AR-10/LR-308 platform adjusts the gas flow by bleeding the gas out of the front of the block instead of restricting the flow like conventional adjustable blocks. Results: The pressure used...
suparms.com
Click to expand...
He has an adjustable gas block. Just doesn't know the brand.
 
11B CIB said:
That’s for pinning the block. Not necessary but some barrels have predrilled holes for them and others have jigs to drill them.

I keep an old block that I use as a dimpling jig for set screws if the barrel has only one or none from the factory. I do it on my drill press but never done the complete pass through for pinning the block. If I had an M16A1, I’d probably pin it

Picture borrowed from Google images
MAbNAlS.png



What brand of barrel are you using? If it’s a common one, the port size might be available online. Might be a perfect time for an adjustable gas block. I like superlative bleed off blocks; they allow excess gas beyond your tuned setting to vent out the front of the block reducing fouling/carbon buildup, pressure, blowback, felt recoil, and temperature

And yes, they’re worth the cost especially suppressed. I run adjustable gas on ALL my semi autos
suparms.com

.750" Adjustable Gas Block, Bleed Off - Solid, Set Screw - Melonite Finish

SKU # SABO-DI-750SM The Superlative Arms Patented “Bleed Off”, direct impingement, gas block for the AR-15/AR-10/LR-308 platform adjusts the gas flow by bleeding the gas out of the front of the block instead of restricting the flow like conventional adjustable blocks. Results: The pressure used...
suparms.com
Click to expand...
11b CIB, Thanks for the answer to the pin. I do not think that the block was drilled for pin. I have a superlative gas block on one of my guns and when tuning it, I did not set it up for any bleed off. They were hard to get about 6-8 months ago and I think that I set up an account with them as a dealer.
 
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I am using an AR-Stoner Barrel 5.56x45 M4 contour with a 1:7 twist. Here is a picture of the block that I am using.20230329_211635.jpg20230329_211655.jpg


​

 
KnotRight said:
I am using an AR-Stoner Barrel 5.56x45 M4 contour with a 1:7 twist. Here is a picture of the block that I am using.View attachment 600864View attachment 600865


​

Click to expand...

That pin looks too large to be some sort of roll pin replacement/alternative. It’s 100% smooth, right?


Is there a sort of set screw on the FRONT of the block? Typically those side adjustment types have a set screw in the front that locks the setting into place.

Not a fan of these random restrictive blocks. It’ll dump the gas back into the barrel and the screw will eventually seize up with carbon. I didn’t see an adjustable block at midway or brownells like this.
 
11B CIB said:
I jThat pin looks too large to be some sort of roll pin replacement/alternative. It’s 100% smooth, right?


Is there a sort of set screw on the FRONT of the block? Typically those side adjustment types have a set screw in the front that locks the setting into place.

Not a fan of these random restrictive blocks. It’ll dump the gas back into the barrel and the screw will eventually seize up with carbon. I didn’t see an adjustable block at midway or brownells like this.
Click to expand...
I put the gun back in the safe and heading out of town in the morning for the weekend. I will check it when I get back.
 
What buffer weight are you running? 10.5s can be pretty violent, stepping up the buffer weight might be the move. My old 10.3 FN barrel needed a H3 and was still pretty violent, kinda the nature of the beast.

I'm personally not a big fan of adjustable gas blocks on ARs, and in my opinion a barrel that requires one isn't a barrel worth having.
 
Cole_McD said:
What buffer weight are you running? 10.5s can be pretty violent, stepping up the buffer weight might be the move. My old 10.3 FN barrel needed a H3 and was still pretty violent, kinda the nature of the beast.

I'm personally not a big fan of adjustable gas blocks on ARs, and in my opinion a barrel that requires one isn't a barrel worth having.
Click to expand...
I think it is and H2. I have a few buffer in the cabinet and will check to see I have an H3.
 
I just went to see what buffers that I have on hand.thought that I had 4 but I must have used 2 on builds. Below are the 2 that I don't have in a gun.
Also looking at what gas blocks I have on hand and I only got one .750 fixed block and the defective on that is on the 10.5 inch gun. Besides getting a couple more buffers and 2 more gas block on order this next week.

20230330_000354.jpg
 
some adjustable gas blocks will not work with a pistol length gas system. I believe you would be better off to get a new one specifically for a pistol.
 
Phantom said:
some adjustable gas blocks will not work with a pistol length gas system. I believe you would be better off to get a new one specifically for a pistol.
Click to expand...
The gun is 10.5 inches and uses a carbine length gas tube. When it was a 7.5" and used a pistol tube, I got less gas.
 
KnotRight said:
The gun is 10.5 inches and uses a carbine length gas tube. When it was a 7.5" and used a pistol tube, I got less gas.
Click to expand...
The problem with 10.5 is that you have so little dwell time for the system to "pressurize" so to speak. The only way to get them to work reliably is to dump gas back violently in the short time you do have. I'm honestly not sure you're going to be able to get picture perfect ejection without significant modifications.

Provided your barrel has a remotely reasonable gas port size, your best bet is to tune the buffer to tame the carrier speed as much as reasonably possible and accept that it's going to recoil more. Again, it's kind of the nature of the beast. Especially if this is a candidate for defensive use, I don't know that I'd worry too much about playing with special gas blocks, gas tubes, or carriers.

The other con, is that you're necessarily going to have increased parts wear with those increased bolt carrier velocities, especially suppressed. Annecdotal, but I killed a carbine spring in my 10.3 at like 5k rounds 😅. Replaced it with a geissele super 42 (H3), but it's still a bandaid on a larger problem.

10.5 is the minimum for most people for terminal performance of the round, but it's still really compromising a lot of parts longevity and general shooting performance. The best you can do it get a barrel with a crane spec gas port and just buffer the crap out of it.

If it's not a defensive use candidate ignore me and have fun tinkering with your blaster!
 
Cole_McD said:
The problem with 10.5 is that you have so little dwell time for the system to "pressurize" so to speak. The only way to get them to work reliably is to dump gas back violently in the short time you do have. I'm honestly not sure you're going to be able to get picture perfect ejection without significant modifications.
Click to expand...
My 10.5” works wonderfully suppresssed and Unsuppressed with the right buffer weight and SLR adjustable block.
 
KnotRight said:
I just went to see what buffers that I have on hand.thought that I had 4 but I must have used 2 on builds. Below are the 2 that I don't have in a gun.
Also looking at what gas blocks I have on hand and I only got one .750 fixed block and the defective on that is on the 10.5 inch gun. Besides getting a couple more buffers and 2 more gas block on order this next week.

View attachment 600914
Click to expand...

That might be an H3 if it’s almost 6oz
 
Lucky63 said:
I just measured my gas block roll pins. Same exact length.

Are you ever going to shoot unsuppressed?
Click to expand...
NOPE!!! Way to loud. If shot in doors, I think it would bust your ear drums and everybody in the house too
 
Me. said:
This is the second thread I read today where someone mentioned the "o'clock" direction their brass leaves the gun.


I'm no armorer...is this something I'm supposed to care about?

All I've ever paid attention to is whether a round ejects, and whether the next chambers.
Click to expand...

22671928017_8c68eccc92_b-2493422359.jpg

generally speaking, the direction in which the brass leaves the gun is an indicator of carrier speed, regardless of mass. an ideal ejection is somewhere between 3-4:30

the system will run if over gassed but is harder on the gun and less pleasant to shoot. suppressors exacerbate this when nothing else is changed after adding the can.

many barrel manufactures deliberately over gas their barrels so the operational window is wider and will allow the casual shooter to run the cheapest steel ammo available with standard components.

once upon a time BCM barrels were notoriously undergassed and would only run with m193 or good brass clones. people whined long enough that they opened the ports up and now their barrels have to be some of the most overgassed barrels you can buy.

ill echo the use of BRT's gas tubes mentioned above in lieu of an adjustable gas block. Ive used several and they work amazingly well.
 
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