SBR Gas question

inkd · Nov 2, 2014

I finally got everything together for my SBR and ran a few rounds through it in 5.56 and 300blk.

In 5.56, it's kicking the brass forward, which I was told was a sign of being overgassed? I put a H buffer in it and it's still kicking them forward. It's a left hand Stag upper at 10.5in

My lefty 300blk is 9in and seems to be kicking them out the proper direction with both 220 and 147gr. Each case has a good sized nick on the casing midway up though.

Will the over gas accelerate the wear on the 5.56 upper? Is there a heavier buffer out there that would fix this? I would prefer to not have to mess with the gas block or tube but will if I need to.

bobthefisher · Nov 2, 2014

What's your gas length, carbine or pistol? You might want to try a longer buffer spring.

erwos · Nov 2, 2014

Yes, you could try an H2 or H3 buffer. What angle are they shooting forward at?

outrider58 · Nov 2, 2014

This is where I keep my mouth shut and my ears open.

Flipz · Nov 2, 2014

erwos said:
Yes, you could try an H2 or H3 buffer. What angle are they shooting forward at?

+1

inkd · Nov 2, 2014

bobthefisher said:
What's your gas length, carbine or pistol? You might want to try a longer buffer spring.

Damnit. Knew I left some info out. 300Blk is a pistol length.

Honestly not sure about the 5.56. I had it done at Scott's. I basically told him what length I wanted and let him pick the rest. It's a 10.5in and I can't remember what the minimum length is for a carbine system off the top of my head.

Lower is a Knight's Armament. Buffer is Marked SR-15. I never measured the spring out though.

inkd · Nov 2, 2014

erwos said:
Yes, you could try an H2 or H3 buffer. What angle are they shooting forward at?

5.56 is being thrown forward at about the 10 o' clock position(lefty upper).

.300blk 220gr was throwing them at about the 9 o'clock, almost straight to the side of the port.

.147gr seemed to be going back to the correct pattern. But I was hooting out of my attic into the steel target on the ground and my attic is a bit cluttered so I couldn't find all the brass.

Tomorrow I hope to be able to get to the outdoor range and check the pattern properly.

Do you think it would be best to just get both buffers and see which one works the best?

inkd · Nov 2, 2014

outrider58 said:
This is where I keep my mouth shut and my ears open.

Hopefully we can both learn something. I'm not real knowledgeable on the AR platform and even less on the effects of adding a suppressor to a weapons system.

Kingjamez · Nov 2, 2014

Do you have an adjustable gas block? I far prefer an adjustable block over guessing at the right buffer weight.

-Jim

1time · Nov 2, 2014

Kingjamez said:
Do you have an adjustable gas block? I far prefer an adjustable block over guessing at the right buffer weight.

-Jim

+1 Get an adjustable gas block, preferably one with detent so it can't adjust itself and tune it until it locks back on an empty mag. Then open it another two or three clicks to make sure.

inkd · Nov 2, 2014

1time said:
+1 Get an adjustable gas block, preferably one with detent so it can't adjust itself and tune it until it locks back on an empty mag. Then open it another two or three clicks to make sure.

I'd prefer to not go that route unless I have to. If I can take care of it with a buffer, I'd prefer that.

Honestly, I have waited long enough to be able to start enjoying these things, I'd prefer to not have to tear them apart.

Klunatic · Nov 2, 2014

Having your gun gassed properly will contribute to a softer kicking, less gas in your face and a more accurate gun. I highly recommend an adjustable gas block especially if you are going to run suppressed/unsuppressed, supersonic/subsonic.

1time · Nov 2, 2014

inkd said:
I'd prefer to not go that route unless I have to. If I can take care of it with a buffer, I'd prefer that.

Honestly, I have waited long enough to be able to start enjoying these things, I'd prefer to not have to tear them apart.

I can understand that. It just seems to me that using a heavier buffer is a band aid masking the fact that it is still over gassed. I could be wrong though, I am not a gunsmith. Maybe Clandestine will be along with an opinion. Its not a hard job to install an adjustable gas block. It's probably as cheap as playing with buffers and springs. Which ever route you go, I hope it works well for you. I love my SBR's.

clandestine · Nov 2, 2014

First thing, the ejection pattern is not always an indicator of gassing. sometimes a bolt head can be the cause due to extractor tension, or a weak ejector spring. Even magazines can cause issues with friction on the carrier or riding over rounds when cycling.

Is this with and without a suppressor? It will be different between the 2. For this application the only GOOD option is adjustable gas, specifically CLICK adjustable gas such as SLR Rifleworks and Syrac Ordnance (I prefer the SLR due to the detent design). With the click adjustable you can measure distinct settings for each type of ammo and for suppressed/unsuppressed applications. Remember, if you go this route adjust the gas when its cold outside (Air is less dense), and the gun is fouled well (NOT CLEAN). If you find your settings on a clean and lubed gun on a hot day it probably wont run when its cold and fouled. IF you go this route its best to use a standard buffer. You don't want a super heavy buffer, just use a standard buffer and the spring below. Extra mass will cause more recoil so keeping things lighter will make it easier to tune. Going too light will make it a game gun and unreliable for serious use. Its a balance.

I wont own another gas operated AR with fixed gas. They will all be equipped with a SLR Gas Block. It guarantees youll be able to run almost any ammo and suppressor without worrying about swapping parts and buffers. Just a click setting change. Adjustable gas will also eliminate almost ALL gas to the face if setup right.

As far as your specific situation, I would first get a Superior Shooting Solutions, Chrome Silicone, Flat Wire Action Spring. They are $30.00 but they last 500k cycles and they don't over compress like a coil spring will. A standard coil spring will only last 4-8k rounds before its optimal to use. These springs also eliminate the "sprong noise" AND they help eliminate carrier bounce. This may give you what your looking for.

If you are not sure about a buffer and have an H Buffer now, then just buy a H2. The H2 has 2 tungsten weights and one steel weight. The H has 1 tungsten weight and 2 steel weights. Just remove a single tungsten from the H, and put in in place of a steel weight in the H2, and violia, you now have an H3.

inkd · Nov 2, 2014

clandestine said:
First thing, the ejection pattern is not always an indicator of gassing. sometimes a bolt head can be the cause due to extractor tension, or a weak ejector spring. Even magazines can cause issues with friction on the carrier or riding over rounds when cycling.

Is this with and without a suppressor? It will be different between the 2. For this application the only GOOD option is adjustable gas, specifically CLICK adjustable gas such as SLR Rifleworks and Syrac Ordnance (I prefer the SLR due to the detent design). With the click adjustable you can measure distinct settings for each type of ammo and for suppressed/unsuppressed applications. Remember, if you go this route adjust the gas when its cold outside (Air is less dense), and the gun is fouled well (NOT CLEAN). If you find your settings on a clean and lubed gun on a hot day it probably wont run when its cold and fouled. IF you go this route its best to use a standard buffer. You don't want a super heavy buffer, just use a standard buffer and the spring below. Extra mass will cause more recoil so keeping things lighter will make it easier to tune. Going too light will make it a game gun and unreliable for serious use. Its a balance.

I wont own another gas operated AR with fixed gas. They will all be equipped with a SLR Gas Block. It guarantees youll be able to run almost any ammo and suppressor without worrying about swapping parts and buffers. Just a click setting change. Adjustable gas will also eliminate almost ALL gas to the face if setup right.

As far as your specific situation, I would first get a Superior Shooting Solutions, Chrome Silicone, Flat Wire Action Spring. They are $30.00 but they last 500k cycles and they don't over compress like a coil spring will. A standard coil spring will only last 4-8k rounds before its optimal to use. These springs also eliminate the "sprong noise" AND they help eliminate carrier bounce. This may give you what your looking for.

If you are not sure about a buffer and have an H Buffer now, then just buy a H2. The H2 has 2 tungsten weights and one steel weight. The H has 1 tungsten weight and 2 steel weights. Just remove a single tungsten from the H, and put in in place of a steel weight in the H2, and violia, you now have an H3.

I was hoping you would see this and chime in. I didn't want to fvck around with changing out gas blocks but you may have sold me with the gas tot he face statement. I was surprised at how much I got while shooting. If I can damn near eliminate that, it would be worth it for me to go to the adjustable gas block.

Can I still run the flat wire spring with that set up?

I'll know more tomorrow about whether it's throwing brass oddly unsuppressed tomorrow after I go to the range. I only shot suppressed tonight. Shooting from my attic kills some of the noise and I do live in the sticks but I don't want to push my luck.

I don't want to set this up, or any of my guns up, as a game gun. My personal preference is to compete with whatever I would intend to defend myself with. I do maybe run my pistol reloads a bit lighter than factory. But not so light that a fly landing on the slide will cause it to malfunction.

clandestine · Nov 2, 2014

inkd said:
I was hoping you would see this and chime in. I didn't want to fvck around with changing out gas blocks but you may have sold me with the gas tot he face statement. I was surprised at how much I got while shooting. If I can damn near eliminate that, it would be worth it for me to go to the adjustable gas block.

Can I still run the flat wire spring with that set up?

I'll know more tomorrow about whether it's throwing brass oddly unsuppressed tomorrow after I go to the range. I only shot suppressed tonight. Shooting from my attic kills some of the noise and I do live in the sticks but I don't want to push my luck.

I don't want to set this up, or any of my guns up, as a game gun. My personal preference is to compete with whatever I would intend to defend myself with. I do maybe run my pistol reloads a bit lighter than factory. But not so light that a fly landing on the slide will cause it to malfunction.

Yes run the flat spring with the adjustable gas but get a standard weight buffer. They are cheap (About $15.00).

You will get less gas to the face once setup right.

I use fireclean lube specifically on the adjuster for the as block because it prevents it from seizing up and it keep carbon from accumulating.

Heres some food for thought on the buffer spring and the adjustable gas blocks.

Adjustable Gas
https://www.youtube.com/watch?v=8msa86o-OcY

Flat Wire Springs
https://www.youtube.com/watch?v=8fMVZbrnvu8&list=UUJudfZAXv2P-FeXTRXSBImg

The above is fine for home defense. You just need to KNOW your ammo settings and find them on a fouled and somewhat dry gun on cold weather to find the the worst conditions it will run with your ammo/suppressor combo. Once I find that setting I back it out 1-2 clicks for safety

inkd · Nov 2, 2014

clandestine said:
Yes run the flat spring with the adjustable gas but get a standard weight buffer. They are cheap (About $15.00).

You will get less gas to the face once setup right.

I use fireclean lube specifically on the adjuster for the as block because it prevents it from seizing up and it keep carbon from accumulating.

Heres some food for thought on the buffer spring and the adjustable gas blocks.

Adjustable Gas
https://www.youtube.com/watch?v=8msa86o-OcY

Flat Wire Springs
https://www.youtube.com/watch?v=8fMVZbrnvu8&list=UUJudfZAXv2P-FeXTRXSBImg

The above is fine for home defense. You just need to KNOW your ammo settings and find them on a fouled and somewhat dry gun on cold weather to find the the worst conditions it will run with your ammo/suppressor combo. Once I find that setting I back it out 1-2 clicks for safety

Cool, I will check them out.

Do I have to pull the existing gas blocks to mic them out to get the diameter or would they be engraved on the block? No big deal if I have to as they will be pulled any ways.

clandestine · Nov 2, 2014

inkd said:
Cool, I will check them out.

Do I have to pull the existing gas blocks to mic them out to get the diameter or would they be engraved on the block? No big deal if I have to as they will be pulled any ways.

5.56 AR? It wont be listed on diameter. Youll have put a caliper on the barrel to be sure.

If its not some thick bull barrel its likely either .625 or .750.

625 is a pencil barrel, and .750 is a what I would call the standard diameter.

Get the set screw model so it can be pinned if you want it to be really secure.

inkd · Nov 2, 2014

clandestine said:
5.56 AR? It wont be listed on diameter. Youll have put a caliper on the barrel to be sure.

If its not some thick bull barrel its likely either .625 or .750.

625 is a pencil barrel, and .750 is a what I would call the standard diameter.

Get the set screw model so it can be pinned if you want it to be really secure.

Okay, definitely not a pencil barrel. I could maybe get a hold of Precision Firearms to ask about the .300, they built it up for me not that long ago and it was turned down from a 1in Shilen blank.

Scott did the 5.56 and it was done from a Stag factory barrel so I would guess that would be at .750 as well?

BradMacc82 · Nov 2, 2014

The Stag SHOULD be a .750", and for a lefty - that ejection is bang-on where all my lefty's were ejecting (carbine length and gas-piston).

SBR Gas question

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