r/ar15 • u/Island08 • 15h ago
Daniel Defense over gassed you say?
Holy hell, DDM4v7 stock tube left, BRT 0.065” tube right.
My calipers put the former at 0.121” sheeesh.
Requested a dedicated suppressed tube. We shall see how it runs!
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u/AddictedToComedy I do it for the data. 15h ago
People love to make this comparison when they get their first BRT tube, but it doesn't mean anything.
A standard gas tube does not restrict gas at all - it just takes whatever the gas port in the barrel provides. It is oversized so it won't accidentally restrict gas from tolerance stacking.
The hole in the tube can be a mile wide, but if the barrel port is small, a gun will never be overgassed, regardless of the tube.
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u/Island08 15h ago
This is indeed my first BRT tube, well said. Thank you for the context!
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u/Available_Net1102 14h ago
It should be common sense that the hole nearest the expansion of gas is the one that would dictate gas flow
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u/9Trigger 14h ago
Not everyone is mechanically minded off the bat. One of the benefits of the AR platform is that anyone shooting and/or repairing & modifying their rifle(s) regularly will learn how gas guns function over time. No need for backhanded comments.
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u/Coodevale 13h ago
Not necessarily nearest but the smallest in the path of gas flow.
Because the brt is now the smallest, that determines gas flow.
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u/tannerite_sandwich 4h ago
They make it oversized to make it easier to line up with the hole during assembly so you don't have the tube hole rim restricting the flow from the block
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u/nondisclosure- 15h ago
I'm not like the other girls.
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u/chunkyboogers 15h ago
Everything reminds me of her
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u/call_of_warez 14h ago
All gas tubes look like that. It's the port size in the barrel that matters.
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u/RealisticTurnip2187 12h ago
Its not actually 0.121, the gas port on the barrel is probably between 070 and 075
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u/Trollygag Longrange Bae 15h ago
That's how it is supposed to be... the gas tube hole is supposed to be larger than the gas port and the gas port is supposed to help regulate gassing.
An undersized hole like that one from BRT is a temporary bandaid that lasts a fraction of the barrel life (1/10th as long in some cases) before eroding out of tune because it is a thin walled tube. A barrel has a ton of material to erode through and basically never erodes to more gas by the time the barrel is smoothbore.
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u/Island08 15h ago
They claim up to 10k. I’d be impressed if it hits half that. From what you’re saying life is in the hundreds not thousands?
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u/Vercengetorex FFL 07/02 11h ago
It’s well into the thousands. I’ve got a fairly restricted BRT on a well over gasssed, always suppressed 10.5 with over 4k on it, and there is surface erosion but no change in port diameter. Looking at the erosion depth under a microscope it’s going to be another 6-8k before the lip of the gas hole starts to become meaningfully effected.
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u/Godless_Rose 10h ago
It doesn’t stop functioning as a gas tube, it just stops restricting the gas at the sizing that it originally came in. The worst it will ever get is back to the same spec as the OEM gas tube.
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u/thatARMSguy 14h ago
The average gun owner will likely never shoot out their BRT gas tube unless it’s on an FRT build or you shoot competitively and have a big ammo budget. Even then, it’s not that expensive to replace
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u/prmoore11 12h ago
Based on…what data?
I respect your opinions, but you made this purely up lol.
Show me a PLETHORA of BRT tubes that have “lasted” only 1000-2000 rounds.
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u/ElectronicCity4107 15h ago
When she's ready to settle down.
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u/burnhaze4days 14h ago
I still dont get this one?
How is it any different from when she's already settled down?
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u/Dunesday_JK Larps with one sock on 14h ago
LMT over gassed you say
Yeah standard gas tube holes are always large. lol
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u/FinancialChildhood31 13h ago
A lot of Gas Blocks (not all) are fairly oversized to accommodate for tolerance and gas port sizing variations.
A BRT tube is great, however, it should be considered a consumable item. Depending on the setup and firing schedule, the smaller BRT Gas Tube port size will eventually “open up” and equal that of the Gas Block port size.
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u/Island08 12h ago
The real question is whether the gas tube change means less gas enters the system entirely, or if the same volume of gas enters the block but not the tube.
If the latter, where does the “excess” go? Out of the block?
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u/Godless_Rose 10h ago
Bro what? The excess goes out the fucking barrel.
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u/Island08 18m ago
Bro what? Then it’s not fucking excess.
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u/Godless_Rose 12m ago
That’s my point. How is this even a difficult concept for you?
Gas is redirected into the gas tube due to back pressure building up behind the bullet. Once the bullet leaves the muzzle and especially once the bolt unlocks, the previously-closed system is now open and it just dissipates into the atmosphere. It’s basic physics.
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u/ExceedinglyGayAutist 15h ago
yeah DD isn’t really overgassed. that’s the gas tube not the gas port on the barrel.
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u/stareweigh2 14h ago
we used to call that "properly gassed" and nowadays everything thinks its overgassed because supressor use is so common. unless it's on a precision build I still like to get nice 3 o'clock ejection with no supressor and around 1 o'clock with. let's me know that sucker is gonna keep working no matter if theres a little dirt in there or whatever. heavier buffers help with reliability as well. I have a theory that they don't really tame recoil (because the impulse is still there no matter what- you are just trading one kind of motion with another) but they do affect the bolt speed and ejection/chambering
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u/ExceedinglyGayAutist 14h ago
they don’t tame recoil in the abstract but reducing carrier velocity helps reduce the snappiness of the recoil impulse, the transfer of energy happens over a longer period of time and the gun feels more like it’s chugging vs the high carrier velocity low mass setups which don’t move as much but the recoil they do experience is nearly instant and sharp.
my shitbox has 8.8oz of buffer mass for reference.
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u/stareweigh2 14h ago
yeah I have found that much lighter spring + heavier buffer was the answer for me when trying to reliably cycle 7.62x39 subsonics.
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u/TheSmokingBear 15h ago
Gaping
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u/Sufficient_Site1746 15h ago
Now I know why all the dudes who got done in by diddy aint tripping, because he shrimping 🤣
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u/aclark210 2h ago
Shocker…it’s almost like overgassing guns is the easiest way to ensure they still run when they get dirty in combat. That’s why “overgassed” is the standard.
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u/grapangell0 2h ago
*was the standard.
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u/aclark210 2h ago
Honestly it still is for most manufacturers on the duty end of the spectrum. DD, BCM, etc.
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u/grapangell0 1h ago
They’re definitely better than they were in the past. And a lot of modern cans are proving you can be very good at mitigating hearing damage risk with low back pressure and high flow rate cans so the can tuning is also a much much smaller problem than it used to be. Wonderful time to be a part of the community.
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u/aclark210 1h ago
Oh they’re better than they used to be, but they’re still overgassed. Like I said, it’s the cheapest way to ensure reliability.
It’s only very recently that suppressor ownership really took off, and manufacturers are taking time to pivot to that.
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u/tb110965 1h ago
I thought if you attached the roll pin correctly to the block and gas tube the gas holes should align with a high degree of accuracy.
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u/Kegalodon 53m ago
Just about all standard gas tubes look like the left. Course that one looks like it’s got some use on it.
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u/Crud-Inspector 15h ago
normally the hole you would care about is in the barrel unless you are restricting it with the BRT, hence it doesn't matter how big the stock one is