Recommend a buffer spring for overgassed

calicojack · Oct 9, 2021

fbi_surveillance_van said:
Huh. Cool setup. I wouldn’t have expected the Radiant to be adding all that much back pressure, but I don’t know the Colt HRT 11.5” gas port specs. In that case I’d definitely suggest just starting with the H3 buffer, see where that gets you.

Out of curiosity, long or short configuration for the Radiant? Are you running the normal end cap or the 5.56 one?

Long with normal 7.62 end cap.

calicojack · Oct 9, 2021

This one

calicojack · Oct 9, 2021

Supposedly, the HRT has a .070" gas port.

clandestine · Oct 9, 2021

Ejection patterns are not important. Ejection consistently in the same place and with without is more important.

SkiPatrolDude · Oct 9, 2021

fbi_surveillance_van said:
It probably won’t harm the rest of the firearm or really hurt you, but the gas tube is already the intended failure point for the AR series of rifles. It’s essentially designed to be the canary in the coal mine for the rest of the firearm. It will fail if run too hard (typically only ever encountered by people doing FA mag dumps, which not many can afford to do at the moment). So you’re intentionally damaging what is already the weakest part of the firearm, and it’s hard to be precise about how much gas you are restricting from coming back into the system. So if you overshoot or undershoot, you have to keep tweaking it, which will further weaken the gas tube.

You’re the one who puts your fingers next to your gas tube when you shoot, not me, so I don’t really care what you do to your firearm. But I wouldn’t personally call it good advice to give out to strangers over the internet.

I was busy all day and so unable to elaborate, but this is essentially where I stand.

Also, a circle turned into an ellipse have equal volume, so unless you’re actually crushing the tube enough to change this volume, you’re not actually doing much of anything. At this point, id argue, you’ve likely weakened the tube considerably.

I will admit this is just a personal hypothesis, but these are not things I ever plan to test in my guns or anyone else’s.

John from MD · Oct 9, 2021

Squashing the tube will make it brittle and it will fail earlier than it's normal life cycle. Depending how it fails, and if any body parts are near it, it can result in a serious wound. 55,000 psi of hot gas is not something I would ever want to meet up with.

clandestine · Oct 10, 2021

Crimping the gas tube is an old way of trying to restrict gas flow. This was done before heavier buffers and springs were available. Before adjustable gas tubes, adjustable gas blocks, adjustable gas keys, and adjustable bolt carriers were a reality. Before restricted gas block inserts and restricted gas tubes existed.

Crimping the gas tube can work but it DOES weaken the gas tube. If you get he tube hot, it often fails at the crimp.

I wouldn't recommend doing it, but it's your gun to do what you want with. If you want to tame the gun down you can buy a BRT Restricted Gas Tube.

woodline · Oct 10, 2021

clandestine said:
Ejection patterns are not important. Ejection consistently in the same place and with without is more important.

Chad, it is wonderful to see you posting here. I hope what advice I provided is not terribly off base, but I would appreciate any corrections or advice you have to offer.

Good to see you around man.

ToBeFree · Oct 10, 2021

Dang it's been awhile since I've seen this.
Good to see ya. Always informative.
Sorry OP.

3paul10 · Oct 10, 2021

Good to see you here Chad!

calicojack · Oct 10, 2021

clandestine said:
Crimping the gas tube is an old way of trying to restrict gas flow. This was done before heavier buffers and springs were available. Before adjustable gas tubes, adjustable gas blocks, adjustable gas keys, and adjustable bolt carriers were a reality. Before restricted gas block inserts and restricted gas tubes existed.

Crimping the gas tube can work but it DOES weaken the gas tube. If you get he tube hot, it often fails at the crimp.

I wouldn't recommend doing it, but it's your gun to do what you want with. If you want to tame the gun down you can buy a BRT Restricted Gas Tube.

Very interesting, Thank you sir!

Looks like BRT's web site lets' you enter in several parameters and they will select a tuned gas tube based on your input.

https://blackrivertactical.com/WP/BRT-EZTUNE-Gas-Tube-Configurable-Carbine-p103167251

calicojack · Oct 10, 2021

There is another reason I like the tuned gas tube option; it would make it easier for me to run this upper on an SBR that has another upper that would not work with an H3 buffer. It's also been pointed out that less gas is less noise out of the port when suppressed.

camo556 · Oct 10, 2021

Yeah having the ability to adjust gas is great esp running suppressed.

JP Enterprises makes an adjustable gas A2 style block also. its $140 but tbh I would do this before I messed around with with a gas tube. edit: mainly because putting a set screw, dimple, or whatever in a thin gas tube seems like a really bad idea.

There is a bcg that has adjustable gas but I've read nothing but problems with these.

outrider58 · Oct 10, 2021

To be honest, ALL my ARs have adjustable gas blocks(SLR), but once I find the sweet spot where my guns run reliably either suppressed or un-suppressed and leave them alone after that.

Upon looking at the JP adjustable A2 type clamp-on and once back in stock, I'll probably pick one up to try.

I've been eye-balling these for a while(below). I'm thinking more for range toys than any serious use, but I like the idea...

https://www.usamade-ar15parts.com/index.php?main_page=product_info&cPath=2_55&products_id=156

I like being able to merely drill a hole through the top of your rail for easy access to the set screw, though, like I said before, I normally don't monkey around with the settings on my guns once I get them tuned up.

woodline · Oct 10, 2021

camo556 said:
Yeah having the ability to adjust gas is great esp running suppressed.

JP Enterprises makes an adjustable gas A2 style block also. its $140 but tbh I would do this before I messed around with with a gas tube. edit: mainly because putting a set screw, dimple, or whatever in a thin gas tube seems like a really bad idea.

There is a bcg that has adjustable gas but I've read nothing but problems with these.

The BRT tube is not adjustable. It is set up from the factory for a certain amount of gas flow, and the guys who work there are suppressor geeks. My assumption was that OP would prefer to knock out a pin and put a new one in vs replace his entire gas block. Personally I prefer to use an adjustable gas block to tune the system so that it functions optimally suppressed, then leave it that way. But that comes with its own set of downsides, so the BRT tubes came to mind as the least intrusive method for restricting gas flow so that uncorking pressure is more optimal for suppressed use. Depending on what he wants to do, he could tune the rifle to function reliably only when suppressed, but I’m going to guess that he’ll opt to restrict gas flow a bit, but not so much that the rifle is under gassed when unsuppressed.

Adjustable carriers were all the rage until at ear suppressor metering became common. Turns out redirecting gas so that it shoots out in a jet next to your ear (and face if shooting southpaw) sort of undermines the whole suppressor concept. For a left handed shooter, they can actually gas you out faster than not using one and just letting the rifle be overgassed.

camo556 · Oct 10, 2021

fbi_surveillance_van said:
The BRT tube is not adjustable. It is set up from the factory for a certain amount of gas flow, and the guys who work there are suppressor geeks. My assumption was that OP would prefer to knock out a pin and put a new one in vs replace his entire gas block. Personally I prefer to use an adjustable gas block to tune the system so that it functions optimally suppressed, then leave it that way. But that comes with its own set of downsides, so the BRT tubes came to mind as the least intrusive method for restricting gas flow so that uncorking pressure is more optimal for suppressed use. Depending on what he wants to do, he could tune the rifle to function reliably only when suppressed, but I’m going to guess that he’ll opt to restrict gas flow a bit, but not so much that the rifle is under gassed when unsuppressed.

Adjustable carriers were all the rage until at ear suppressor metering became common. Turns out redirecting gas so that it shoots out in a jet next to your ear (and face if shooting southpaw) sort of undermines the whole suppressor concept. For a left handed shooter, they can actually gas you out faster than not using one and just letting the rifle be overgassed.

calicojack · Oct 10, 2021

fbi_surveillance_van said:
Depending on what he wants to do, he could tune the rifle to function reliably only when suppressed, but I’m going to guess that he’ll opt to restrict gas flow a bit, but not so much that the rifle is under gassed when unsuppressed.

alucard0822 · Oct 11, 2021

Even with an adjustable gas block you want a heavier buffer, probably an H3. Mass does a lot more to slow the action than a spring, and will run over a wider range of port pressures/conditions. I run adjustable blocks on my 5.56 cal suppressed ARs, best way to cut excess gas and limit port pop. Tune to run unsuppressed, probably a couple clicks past the minimum that locks back on an empty mag, and it will probably run well with or without a can.

calicojack · Oct 11, 2021

outrider58 said:
I've been eye-balling these for a while(below). I'm thinking more for range toys than any serious use, but I like the idea...

I really don't want to remove the securely staked front sight tower on that barrel. Now if an adjustable dohickey will let me adjust the gas without removing the sight tower, that might be worth it.

clandestine · Oct 11, 2021

calicojack said:
I really don't want to remove the securely staked front sight tower on that barrel. Now if an adjustable dohickey will let me adjust the gas without removing the sight tower, that might be worth it.

Adjustable gas tubes have proven to be unreliable in my experience.

Removing the taper pinned FSB does make your gas system less "rugged". Taper pins are the most bomb proof method of attaching a gas block or sight base.

I would also suggest to not initially putting a heavy buffer in your AR if you go adjustable gas route. The entire premise of adjustable gas to to gain a wider range of operation. When you add heavier springs and buffers to adjustable gas you lose the ability to run some types of ammo.

You can add buffers and extra springs later on if necessary but that a last resort, not a first.

I do this stuff every day. I have about $2500 worth of buffers and springs on my wall for bench and class testing purposes.

Recommend a buffer spring for overgassed

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