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9/7/2026 11:48:29 PM EDT
[Last Edit: USMC88-93][Edited]
Recently acquired Daniel Defense MK18 upper and a Knights Armament QDSS NT4 to put on my SBR lower.  I am about to pull the trigger on a Viltor A5 receiver extension.  Those with a high backflow suppressor on a recent manufacture DD MK18 what Viltor buffer are you using when suppressed? I presume the A5H2 would be the choice for unsuppressed but if I were to just buy a second buffer when I get it would you suggest the A5H3 or just go ahead and get the A5H4 for that short of a suppressed barrel?

I have not as of yet shot it with the typical milspec carbine receiver extension and buffer weights.
Plays well with self, and cleverly disguised as a responsible adult.
9/7/2026 11:56:16 PM EDT
[#1]
Our issue guns (CQBRs) with the same setup ran with H3s, which was the heaviest our armorers had.

I would at least get the Vltor H2.
I wanted a mission, and for my sins, they gave me one.
No rules today, sport…just orders.
It’s not about how many people you kill, it’s about how many you save.
9/8/2026 4:42:12 AM EDT
[#2]
A5H3 will most likely be fine. But IMHO, you're better off diverting the gas rather than trying to "outweigh" it. Scaling up the buffer weight just creates a more violent gun.

I would look at one of the gas-diverting BCGs like the LMT enhanced carrier, or even an adjustable one like the Bootleg. With the Bootleg, you don't even need to open the rifle to adjust it. A simple small screwdriver is all you need, via the ejection port. With either of those options, you should be fine with an A5H2 with or without the can.
9/8/2026 7:01:23 AM EDT
[Last Edit: BULLDAWG_556][Edited] [#3]
It’ll depend largely upon the size of the gas port in your barrel, and what BCG you run. I’d measure it so I’d know. But hey I’m OCD that way. I just dropped a brand new Daniel Defense barrel in my Colt CQBR block II clone and it has a measured .070.

A super42 and H3 was to much spring rate and gave me 1:00 ejection with an RC2 and caused malfunctions once rifle got dirty, but that buffer combo is perfect in my 10.3 Super Duty with a Polonium K, as well as a Sandman S.
A Colt spring and Luth AR H3 was almost 12:00 ejection
A Sprinco blue and Luth AR H3 3:00 suppressed and 4:00 unsuppressed.

I’ll replace the Luth AR H3 with a Colt H3 one day. Maybe. The Luth AR appears to be milspec so it isn’t really too important for me to replace.

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