Overgassed solutions

[blksno]

I've started shooting this system a little more often lately and I'm trying to determine the best course of action to improve the obvious over gassing. When I built it nearly a decade ago, I just started with some basic mil spec parts and ran it 50/50 unsuppressed and occasionally suppressed with a .30 cal can. Ran OK in both situations, but not ideal. Going forward it will be run 100% suppressed.

Now that I'm planning to run it a little more often and I'm considering some gas gun LR team matches...I'd like to get it rolling a little smoother before next summer.
5.56 crimped 77gr OTMs at 2630 fps over 20 rounds on the new Garmin chrono

In the clip...
DPMS Mini SASS barrel (18" - 1:8 twist, w/ midlength gas)
Suppressor is a 224 VAPR (better suited for bolt guns) Tight bore, 9" and maximum suppression, but also restricting.
Takes a .936 gas block so I do NOT currently run an adjustable because it won't fit under this lowpro hand guard.
Gen1 Magpul UBR is standard carbine length. In the clip, it has an H3 buffer. 5.65 oz and a mil spec spring.
I've tested Armaspec systems up to H3
I have tested all the way up to a 10oz pistol buffer with an H5 tube and it's still excessive gas and tossing brass to the 1:30 - 2:00 when running suppressed.
Underside of the charge handle is vented to the right (similar to a Gas Buster except the opposite direction) But I think a legitimate handle that redirects excess gas on the top and bottom, away from the face would help too.

Now...here's the 3 options I'm considering. (either way, I'm planning to switch to an A5 system with a Gen2 UBR)

1) New hand guard to accommodate an adjustable .936 gas block I already have in a box somewhere. This is 17" and I'd like to stay in the 16-17.5" length.
2) BRT EZTUNE gas tube extra tight (.0635) and then hopefully get back down to an H3 or H2 buffer and TUBB Flat Wire spring...wouldn't be adjustable, but should make more common buffers work again.
3) Any other suggestions that make sense.

 

[Evintos]

Start with BRT EZTune and mess around with buffer weights. If you find you're still overgassed, add either an adjustable gas key to your bolt carrier or buy an adjustable gas bolt carrier (Bootleg 4 position, Foxtrot Mike 2 position).

You can also skip the BRT EZtune and go with the adjustable gas key, but restricting gas flow at the gas port is (imo) the better solution.

 

[Cascade Hemi]

1) EZ Tube gas tube.
2) Drill and tap gas block port for set screw, drill set screw to desired port size.

 

[rlsmith1]

Personally, I don't run handguards that can't accommodate an adjustable gas block. As standardized as the AR15 is, gas port sizing seems to be the one thing that everyone opens up (which makes sense because it's much easier to restrict than add).

Life is too simple with adjustable gas. As long as you're running a reasonable buffer / spring combo, you should be able to dial your gas into what you need and it will work well suppressed or unsuppressed without changing anything (on a 556 anyway). You can get as optimized as you want, but I typically try to make my rifles function with as wide of a range of loads as possible. Personally, I run an H2 buffer and standard carbine spring (I'd like to try the Tubb sometime though).

When I adjust my gas, I typically start with gas turned way down, and shoot a single round on an empty mag to see if it locks back. I find the minimum setting to lock the bolt back on an empty mag, and then open it one click more. Of course, this is done unsuppressed; with a suppressor I only gain reliability. I have found that if I set my gas based on 77gr 556 loads, I will sometimes have issues with 55gr 223 loads on the same gas setting if shooting unsuppressed (which is why I sometimes open up a second click). Anything with a suppressor works fine due to the increased back pressure.

What is appealing to me about the EZ Tune is that you can adjust gas on the fly much easier (something that is really relevant on an AR10). I don't find my self adjusting gas at all on my AR15's once they are set (however, I'm not competing and looking for the absolute softest shooting rifle).

Hope that helps!

 

[redneckbmxer24]

Probably not what you want to hear but I’d swap the barrel. DPMS barrels have large gas ports, a mid length on an 18” is far less than ideal, and it’s too fat to accommodate an adjustable gas block under the HG. It’s got a lot working against you.

I’d pick up a quality 18” rifle gas .750 journal barrel and a good AGB like a superlative. You’ll get a better suited system and probably a more accurate barrel in the process.

 

[mettee]

^ this

While its going to cost you some greenbacks, the benefit of a good barrel with the proper specs will quickly make it worthwhile.

And absolutely go with an A5 system and SA gas block.

 

[saddlerocker]

I did the BRT gas tube on an older overgassed 11.5" DD barrel and its awesome.
It will erode and open up over time. The owner or someone who posts on arfcom tested a few for erosion and I think he said they hold up for ~5krds.
But it was so simple and theyll make you whatever size you want.
Cheap fix, especially if your shooting suppressed all the time and dont need to adjust.

 

[MuleyTime]

This is what I'm going through now. Mine is a 6DTI (6X6.8 improved) always suppressed and it’s always been over gassed. I've tried all different buffer weights but no dice. I ordered an .875 SA Gas Block which will be delivered today. Hopefully I will get to test today or tomorrow.

Btw, I was also concerned about the Hand Guard but I think it’s going to work with my Odinworks….fingers crossed.

Edit: SA Block installed and fit without issue under the Odinworks hand guard.

 

[msgriff]

Barnes Precision adjustable gas tube. Unless your rail has weight reduction slots on the top (like some Aero's) that happen to line up, you'll have to drill a hole through the top for a hex wrench. Or remove the handguard to adjust. Just adding to the options, I would prefer most of the others methods previously mentioned.

 

[223Rem]

Ok, real simple fix for an overgassed system...try moving the gas block up a bit. Its works two fold by obsuring the gas port a bit and lets in a little more gas to the carrier key area before cycling the action.

 

[Clint H]

A few companies make adjustable gas keys for the BCG.

RCA Adjustable Gas Key - Welcome to Rubber City Armory

Made from Pre-Hardened 4140: 28-32RC with radiused corners reducing sharp edges. Enhances performance of low mass and standard mass GI systems without unnecessary dissassembly. Gas flow is adjusted and maintained at the carrier with set screws. One to adjust gas flow and one to lock it in place...

rubbercityarmory.com

 

[Ronws]

I am not even sure I can help, other than to tell of my own experience. I have a Windham Weaponry R16SFST-308.

Before shooting it in the carbine configuration (T stands for telescoping stock,) I changed to a rifle stock and installed a Magpul PRS Gen III adjustable stock, which came with a new buffer that turned out to be too light. I had to mix and match and get the buffer assembly up to 6.1 ounces to stop the overgassing problem. That rifle has DI system with a mid-length gas block that is not adjustable. Increasing to 6.1 oucnes solved the problem for my 168 gr BTHP.

 

[blksno]

Well, after some phone calls and suggestions from here...I think I'm pretty close to perfect.
Picked up a pair of Sprinco buffer springs. Both an Orange (EXTRA EXTRA power) as well as Red (Extra Power) and then also opted for a BRT-EZTUNE Gas Tube (.0635 smallest they make) knowing that if the combo was too restrictive I could always go down to a H3, H2 or even H1 buffer.

Turns out, that's exactly what worked.

Started out with the Orange spring and H1 buffer. Perfect 4:00 ejection but I did have a mis-feed and no bolt lock back.
Went to the Red spring and H1 buffer and it seems to be running perfect. Only ran a couple rounds, but it was amazing how much recoil was reduced as well. Less mass going backward at a slower speed...and a stronger spring to prevent it from smashing into the back of the buffer.

Might get a video tomorrow.
The Sprinco springs were recommended by a buddy and I'm glad I went that route. I may actually end up grabbing one more Blue (Enhanced power) just to have on the shelf as a means to test other builds in the future.
Even though ejection seems perfect...the suppressor still has a pinch of excess gas in the face. MUCH MUCH MUCH less than before...but I think it would help to swap the hand guard, put the adjustable gas block on, and have a slightly lighter spring to fine tune things.

 

[Cascade Hemi]

Well, after some phone calls and suggestions from here...I think I'm pretty close to perfect.
Picked up a pair of Sprinco buffer springs. Both an Orange (EXTRA EXTRA power) as well as Red (Extra Power) and then also opted for a BRT-EZTUNE Gas Tube (.0635 smallest they make) knowing that if the combo was too restrictive I could always go down to a H3, H2 or even H1 buffer.

Turns out, that's exactly what worked.

Started out with the Orange spring and H1 buffer. Perfect 4:00 ejection but I did have a mis-feed and no bolt lock back.
Went to the Red spring and H1 buffer and it seems to be running perfect. Only ran a couple rounds, but it was amazing how much recoil was reduced as well. Less mass going backward at a slower speed...and a stronger spring to prevent it from smashing into the back of the buffer.

Might get a video tomorrow.
The Sprinco springs were recommended by a buddy and I'm glad I went that route. I may actually end up grabbing one more Blue (Enhanced power) just to have on the shelf as a means to test other builds in the future.
Even though ejection seems perfect...the suppressor still has a pinch of excess gas in the face. MUCH MUCH MUCH less than before...but I think it would help to swap the hand guard, put the adjustable gas block on, and have a slightly lighter spring to fine tune things.

For that application I would want no more than blue spring and H1 buffer. An adjustable gas block would be a much better option because of the long dwell and silencer.