View Full Version : Adjustable gas block or adjustable bolt carrier?
snackgunner
06-21-18, 14:55
Trying to finish up my build on paper. Last decision i need to make is to go with an adjustable gas block or a adjustable bolt carrier for my suppressed sbr build.
Https://www.brownells.com/rifle-parts/gas-system-parts/gas-blocks/ar-15-sentry-adjustable-gas-blocks-steel-set-screw-prod109890.aspx?avs%7cManufacturer_1=SLR%2bRIFLEWORKS
Https://www.rainierarms.com/bootleg-adjustable-carrier-5-56/
Ive read on here of members having a high round count on these adjustable gas blocks and they because of the high round count they would seuze up. With the suppressed bcg there are no springs or pins to mess with.
Anyone who has used both the adjustable gas blocks and adjustable/suppressed bcgs? Which one do you prefer?
Has anyone had an adjustable gas block lock up/seize up on them?
Why not just use a properly gassed barrel?? It doesn't have ANY moving parts. Remember Murphy.
my readings indicated that where the gas is stopped or released is important
i didn't want waste gas/fouling/heat inside my upper so i decided on a gas block
nor did i want the built-up back-pressure being forced back out the can (causing more heat and noise), so i chose a proven bleed-off gas block that dumps gases forward of the block
after many rounds, none of my Superlative Arms gas blocks have seized up, the adjustment screw turns just as it did when new
check out mike's (aka: mbell556) you-tube vids on them
https://www.youtube.com/embed/UwHA9pvkgYA
https://www.youtube.com/embed/0y02vdDzRUk
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note: i'm just a user and have no tie to this company
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Is the SBR going to be 100% suppressed or 50/50 mixed use?
A dedicated suppressed setup should have a properly sized non-adjustable gas port.
snackgunner
06-21-18, 21:56
50/50
5.56 Bonded SP
06-21-18, 23:57
A properly gassed barrel on a di gun is probably your best way to go. The only adjustable gas block systems I like are on long stroke piston guns like the sig 556.
Adjustable bcgs are a waste of money from what I recall. If you are set on going ajustable, I would research the most durable adjustable gas block, a lot of them come loose from what I recall.
boombotz401
06-22-18, 03:24
How does one find a barrel with a port designed for suppressed?
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diving dave
06-22-18, 10:33
I run the bootleg carrier. It has made a huge difference in my 6.8 with a can, which was really overgassed. Only issue I have as a lefty, is when really getting on the trigger it is gassy out the ejection port, but function has been 100%.
How does one find a barrel with a port designed for suppressed?
There are generally only a couple ways to get a small port.
1) Get a 16" carbine barrel cut down to 10.5-11.5"
2) Contact a savvy barrel mfg and ask for a specific gas port
3) Get one of our MicroTUNE gas blocks (http://www.blackrivertactical.com/concrete5/store/#!/BRT-MicroTUNE-Adjustable-Gas-Block-750/p/102156493/category=6464009) with a fixed port of your choice
Now a dedicated suppressed SBR will allow the smallest port and best operation with the suppressor, but generally won't function without it.
Mixing suppressed and un-suppressed use involves a large series of different compromises around gassing, function, springs, buffers and adjustable gas devices.
There are generally only a couple ways to get a small port.
1) Get a 16" carbine barrel cut down to 10.5-11.5"
2) Contact a savvy barrel mfg and ask for a specific gas port
3) Get one of our MicroTUNE gas blocks (http://www.blackrivertactical.com/concrete5/store/#!/BRT-MicroTUNE-Adjustable-Gas-Block-750/p/102156493/category=6464009) with a fixed port of your choice
Now a dedicated suppressed SBR will allow the smallest port and best operation with the suppressor, but generally won't function without it.
Mixing suppressed and un-suppressed use involves a large series of different compromises around gassing, function, springs, buffers and adjustable gas devices.
Your BRT EZ tune gas tube is also an option I like. Especially with pin and welded muzzle devices now you can easily tune the amount of gas driving your rifle exactly how you want it
Of the two options, Gas Block all the way.
50/50
The reality is, you will shoot your shorty AR suppressed 100% of the time. Might as well tune it to match. Tune Once. Cry Once.
I don't feel like searching for you but there is an extensive thread about the ultimate sbr somewhere on the forum. Users discussed the LMT Enhanced BCG, sprinco spring, and A5 tube and buffers...
I’m surprised this thread has got this deep and no one has asked what barrel are you planning on running?
You might not even need those options. If you get the right barrel a LMT Enhanced BCG might do you well, that and a GB from Clint maybe all you need.
snackgunner
06-23-18, 05:25
. Might as well tune it to match
How do you suggest doing that?
snackgunner
06-23-18, 05:34
I’m surprised this thread has got this deep and no one has asked what barrel are you planning on running?
You might not even need those options. If you get the right barrel a LMT Enhanced BCG might do you well, that and a GB from Clint maybe all you need.
11.5 inch barrel
How do you suggest doing that?
Options are a reduced gas port barrel like the sionics, an adjustable gas block like the SLR, or you can go with the BRT CustomTUNE Gas Ports.
If you actually run the gun 50/50 then the adjustable BCG is a good option but if you are going to run the gun suppressed all the time, the above options are the way to go.
I prefer an adjustable gas block as I change ammo depending on what is cheaper at the time. My gas block is JP and I haven't had any problems with it.
Ned Christiansen
06-23-18, 09:32
I find this very convenient:
https://innovativearms.com/war/
To me, "dedicated" also means "severely restricted versatility". I don't like the idea of a gun that doesn't work when you remove an accessory.
The further upstream you choke the gas off, the better, but so many gas block options are not easy to operate. The adjustable bolt carrier doesn't check the gas before it gets into the carrier, it lets it all in and vents the excess. That means more ejection port noise and gas in the face.
The WAR restricts it from getting into the carrier and is super simple to use. It's not the cheapest nor the easiest to incorporate but is sure works well.
I find this very convenient:
https://innovativearms.com/war/
To me, "dedicated" also means "severely restricted versatility". I don't like the idea of a gun that doesn't work when you remove an accessory.
The further upstream you choke the gas off, the better, but so many gas block options are not easy to operate. The adjustable bolt carrier doesn't check the gas before it gets into the carrier, it lets it all in and vents the excess. That means more ejection port noise and gas in the face.
The WAR restricts it from getting into the carrier and is super simple to use. It's not the cheapest nor the easiest to incorporate but is sure works well.
Below are some answered questions on the WAR adjustabe receiver :
What comes with the W.A.R. ? Forward assist, and dust cover assembly already installed, and one proprietary gas tube in either, pistol, carbine, or midlength.
Does it have a M4 feed ramp? Yes. The W.A.R. is a mil spec, forged upper receiver, with M4 feed ramps, machined for the killswitch and type 3 hardcoat anodized.
Can I shut the gas off? Yes. If you place the lever in between the two settings the gas is turned off.
Can I use the W.A.R. with .300 blk ? Yes and No. You can use only .300 blk high velocity with the pistol length gas system in both settings. Due to the low pressure of .300 blk subsonic, the rifle will not cycle while in the suppressed setting. The rifle will always function properly with any ammunition in the unsuppressed setting, even when a silencer is used.
What calibers can I use with the W.A.R.? 5.56, .223, 6.5, 6.8 spc, 7.62 x 39, 5.45 x 39, and .300 blk HV.
Can I use a 7.62 (.308) silencer? Yes. However, not all silencers are created equal, and some may not produce enough back pressure to cycle reliably. The W.A.R. requires a quality silencer.
Do I have to use a special gas tube? Yes, the W.A.R. includes one proprietary gas tube in either pistol, carbine or midlength. Additional gas tubes are available separately.
Can I take the killswitch apart to clean it? No. The W.A.R. parts do not require any maintenance, and are not for disassembly by the end user.
Can I buy replacement parts? No. Replacement parts are not sold separately, except for additional gas tubes. The W.A.R. has a 100% warranty. If required, you would send in your W.A.R. upper for inspection, and parts may be repaired or replaced at our facility.
What is the warranty? All products manufactured by Innovative Arms have a 100% warranty. WARRANTY & FAQ
Which manufactures have barrels with the correct gas port hole size of .084 – .093? There are a number of AR manufactures that outsource their barrels, and they may change their sources without notice. Because of this we are not able to list specific manufactures with any certainty. You will need to contact the manufacturer of the particular rifle you are using to verify their gas port hole size.
I find this very convenient:
https://innovativearms.com/war/
To me, "dedicated" also means "severely restricted versatility". I don't like the idea of a gun that doesn't work when you remove an accessory.
The further upstream you choke the gas off, the better, but so many gas block options are not easy to operate. The adjustable bolt carrier doesn't check the gas before it gets into the carrier, it lets it all in and vents the excess. That means more ejection port noise and gas in the face.
The WAR restricts it from getting into the carrier and is super simple to use. It's not the cheapest nor the easiest to incorporate but is sure works well.
Very cool. I had never seen that before. I will have to check it out on my next build.
No issue with the switch getting in the way or hung up on gear?
11.5 inch barrel
Then if I were you, I would get the LMT Enhanced BCG, paired with the Sionics RGP 11.5 barrel and call it a day.
To me, "dedicated" also means "severely restricted versatility". I don't like the idea of a gun that doesn't work when you remove an accessory.
You make a very good point, Ned. I have a shorty upper tuned to run smoothly and reliably with a suppressor, but it must be cycled by hand when shot without the suppressor. It has an SLR adjustable gas block. It's not as easy to adjust as the WAR upper you linked to, but I can adjust it with an Allen key.
How do you suggest doing that?
Based on my hands-on experience, I would use an 11.5" barrel, A5 RE, A5H2 buffer, Sprinco green spring, standard full auto BCG from a known and trusted maker, Colt or Sprinco M4 extractor spring and an SLR adjustable gas block (assuming the gas port is larger than needed for suppressed work). I have not used the WAR upper, but you can trust Ned when it comes to evaluating parts.
To tune the rifle to run optimally with a suppressor, start with a lock back check. I usually start with the gas block opened up so the rifle fires, ejects and locks back on an empty mag. This prevents cases from getting stuck in the chamber. Shooting one round at a time, I close the gas valve until the round ejects, but does not lock back. Then, I open the gas block until it ejects and locks back. Of course, this is performed with the suppressor installed.
To tune an AR to run suppressed and unsupressed, perform the lock back check as above with two differences. First, tune the rifle without the suppressor. Second, tune the rifle so it ejects but does not lock back. Then test it with the suppressor installed. It should eject and lock back. The rifle won't be in optimal tune for either mode, but it will work without being horribly overgassed.
I have also had good luck tuning with a carbine RE and H2 buffer. The H buffer also works well, but the H2 is a little better. I would recommend staying away from a carbine weight buffer as it's too light. Don't let anyone tell you the H2 is a heavy buffer. In fact, the H2 is lighter than the original rifle buffer.
You don't have to use the SLR gas block. Black River Tactical offers micro ports than can be installed in the gas block to restrict gas flow. You can play with different port diameters until the tune your looking for is achieved. The downside is that the gas block has to be removed before a port can be installed or changed.
BRT also offers gas tubes with restricted ports. They are much easier to swap than the micro ports. I haven't tried the gas tubes yet, but the theory is sound and simple
I am currently using the BRT micro port in one upper and the SLR AGB in another. I am quite satisfied with the performance of both as well as the customer service provided by both makers. As I said above, I haven't used the WAR upper or the BRT gas tube.
I haven't said anything about the LMT enhanced carrier. Initially, it worked better than a standard carrier, but it developed a problem that I will not go into until I've had a chance to contact LMT to get it resolved.
Why not just use a properly gassed barrel?? It doesn't have ANY moving parts. Remember Murphy.
I have a few adjustable gas blocks sitting here in my various parts bins, and never end up installing them. A standard gas block does everything I need, though no doubt with a bit less grace. Don't get me wrong, I have some adjustable gas block weapons which came that way, but for my own builds I seem to rely on the more proven siblings.
I can say that a Sionics 11.5" LW, BRT .067" gas port, LMT E-carrier, A5H2, and Tubbs AR10 spring runs fine in moderate temps on 5.56 pressure ammo, unsuppressed, though I haven't put a large number of rounds through it. I'm fairly certain that it would work fine with a smaller port as well. I don't see why you can't have your cake and eat it, too.
Mist, when you are able, I'd be interested to hear more about your experience with the E-carrier.
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Ned Christiansen
06-27-18, 07:42
No hangups with the switch on the W.A.R. upper but I did take a file to the latest one and take a few sharp edges off.
I got a couple pf PMs about my experience with the LMT Enhanced Carrier. The trouble I had with it is is suddenly started short stroking. Troubleshooting the problem isolated it to the carrier. Changing to a bolt with good gas rings didn't fix the problem and the gas key bolts were tight. I swapped the BCG and got the AR running for an important range trip. I put the LMT away because I was tired of dealing with it. But the recent PMs prodded me into taking another look at it.
First, I removed the key only to find a layer of oil and carbon underneath. It was definitely leaking. I cleaned the mating surfaces and re-installed the key. I then took a close look at the bolt I'd been using with the LMT carrier. The bolt worked fine in another carrier, so I didn't think anything about it. Today, I removed the gas rings and was surprised to see they were quite worn. I replaced them. Initial test firing showed no signs of short stroking or leaking.
I also have the Enhanced Bolt, one of the earliest ones that didn't work well. I never used it because it had problems with failure to eject due to weak extraction. The LMT bolt uses two extractor springs and they are smaller in diameter than the standard spring. It's the same diameter as one of the springs from a lower parts kit. I think it's the spring for the safety detent. I counted the number of coils of the old extractor springs and got 11. I counted 11 coils of the potential donor spring and found the length would be longer. I cut the donor spring in half and got about 10 coils after some clean up. The springs were longer than the originals and stiffened the extractor significantly. The failure to eject due to weak extraction was eliminated. In fact, I was surprised to see ejection angle and distance was very consistent.
I tested the LMT BCG with the enhanced bolt in my two suppressed ARs on two different lowers. One is equipped with an H2 buffer, the other with an A5H2. The LMT seemed to have a bit softer recoil impulse. It also ran on the same setting as a standard BCG on the adjustable gas block upper. I only had a handful of rounds to test with today, but so far, the results look promising.
I also have the Enhanced Bolt, one of the earliest ones that didn't work well. I never used it because it had problems with failure to eject due to weak extraction. The LMT bolt uses two extractor springs and they are smaller in diameter than the standard spring. It's the same diameter as one of the springs from a lower parts kit. I think it's the spring for the safety detent. I counted the number of coils of the old extractor springs and got 11. I counted 11 coils of the potential donor spring and found the length would be longer. I cut the donor spring in half and got about 10 coils after some clean up. The springs were longer than the originals and stiffened the extractor significantly. The failure to eject due to weak extraction was eliminated. In fact, I was surprised to see ejection angle and distance was very consistent.
I had two of the enhanced bolts in use and started having extraction issues also. I guess the springs weakened some through use because they got a good number of cycles before they had any signs of trouble. Rather than try to fix them, I just got rid of them. If I end up with another one, I'll definitely try what you're doing.
And regarding the subject of the thread, I prefer the Gemtech and Bootleg carriers for gas regulation when shooting suppressed. I used to use the LMT enhanced carriers a lot also, but I never got the same kind of results I get with the G and B carriers.
Why not just use a properly gassed barrel?? It doesn't have ANY moving parts. Remember Murphy.
This. I dont use shitty barrels or foot long suppressors. My guns run flawlessly and cleanly.
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