The right buffer weights for two different AR-15 uppers

[MrDisaster]

Hi everyone! it's my first post here.

I'm building 2 uppers for my AR-15 lower (I'll run same lower for both upper because, in terms of the law in my country, it's impossible to purchase extra lower).
The purpose of those uppers is a Short Tactical Carabine and Long Range PRS rifle.

Here's listed the properties for both uppers.

12.5'' Tactical Carabine:
- Barrel: Criterion CORE Series 12.5
- Twist: 1:8
- Gas Length: Carabine
- Gas Block: Superlative Arms Adjustable Gas Block 0.625''

24'' Long Range PRS rifle:
- Barrel: Criterion 24 inch bull barrel
- Twist: 1:8
- Gas Length: Rifle
- Gas Block: Superlative Arms Adjustable Gas Block 0.936''

I was adviced to replace my current mil-spec buffer system with VLTOR A5 Buffer System, to deal with possible malfunctions. And here comes my headache, I don't know how to choose the right buffer weights for operating with those two uppers. If there's any rules to follow for determining the right buffer weights, I'd prefer to do so, instead of purchasing all kinds of A5 Buffers and finding the right ones in practice.

 

[wade2big]

Use the receiver extension you have and pick up a H3 buffer for the 12.5”. I would wager the 24” upper will run just fine with the H3 as well.

 

[msgriff]

How was the serialized component (lower) originally transferred to you as, rifle, pistol, or other?

 

[longshot2000]

The real truth is there is no real truth. A rifle will behave as a system. The cartridge, the barrel length, the gas system (carbine, rifle, etc.), the gas port size, the BCG weight, the spring tension and the buffer weight. I liken to shoes. a 10-1/2 Wide is different for each shoe, and what socks you wear, etc. There are some generalizations, but you will likely need to dial-in your weights on the buffer.

I would first cry BS on needing to replace a milspec buffer tube. Might the Veltor system give you additional options? Yes, just like the adjustable gas block, and you may want that. But I would start with what you have.

Generally speaking, a shorter barrel on a carbine gas barrel will need extra weight. But it might not, depending upon the gas port size. I would start with an H1 on the 12.5" and see if you are getting proper cycling and ejection. For the rifle, maybe I missed it, but are you using a carbine or rifle buffer? If carbine, I would keep at standard, H0.

From there, add weights as needed. For example, we sell the individual tungsten weights: Carbine Tungsten weights If you see below, the Heavy weights are a function of how many weights are steel v. tungsten. There are three weights inside a carbine buffer. The standard H0 is 3 steel, and H3 is 3 tungsten:

From this, you can see how you can configure your own buffer, just by buying a few weights and opening up the buffer with a punch. There is a lateral pin that holds the rubber stopper in. If you punch it out, the weights and spacers are accessible.

I would try this first.

 

[supercorndogs]

Adjustable gas block an option? Adjust gas to the lower, don't adjust the lower to the gas.

 

[AK4900PA]

It's going to require some trial and error. I swap between a 4.5" 22lr, 4.75" 300blk and a 12.5" 6.5 Grendel on the same lower. I use a 3.3oz buffer. The blackout has a standard fixed gas block while the Grendel uses a SLR adjustable gas block. Works well for me.

 

[MrDisaster]

How was the serialized component (lower) originally transferred to you as, rifle, pistol, or other?

I purchased Armalite M-15 in the gun store and I'm going to use it's lower now. It might sound weird, but here you can buy as many guns as you wish in the store, but you can not import lower receiver, even if you request permit for import and going to register it

 

[thedude824]

You've got an adjustable gas block on both uppers. Im a fan of the A5 system so I'll leave it there. Given you have adjustable gas blocks on both uppers, get the H2 buffer and adjust the gas on each upper. Its really a non-issue.

 

[S197]

Hi everyone! it's my first post here.

I'm building 2 uppers for my AR-15 lower (I'll run same lower for both upper because, in terms of the law in my country, it's impossible to purchase extra lower).
The purpose of those uppers is a Short Tactical Carabine and Long Range PRS rifle.

Here's listed the properties for both uppers.

12.5'' Tactical Carabine:
- Barrel: Criterion CORE Series 12.5
- Twist: 1:8
- Gas Length: Carabine
- Gas Block: Superlative Arms Adjustable Gas Block 0.625''

24'' Long Range PRS rifle:
- Barrel: Criterion 24 inch bull barrel
- Twist: 1:8
- Gas Length: Rifle
- Gas Block: Superlative Arms Adjustable Gas Block 0.936''

I was adviced to replace my current mil-spec buffer system with VLTOR A5 Buffer System, to deal with possible malfunctions. And here comes my headache, I don't know how to choose the right buffer weights for operating with those two uppers. If there's any rules to follow for determining the right buffer weights, I'd prefer to do so, instead of purchasing all kinds of A5 Buffers and finding the right ones in practice.

With an adjustable gb you will not need to change the weights out.

 

[Clayman]

A5-H2 and tune each upper. H3 is not necessary unsuppressed on 12.5 with an agb.

 

[Desert_Racer]

Gassing on a carbine length 12.5 and a rifle length 24 inch barrel are at the complete opposite ends of the spectrum.

My opinion: you will have issues if you buy one buffer weight and try to make it work for both. I would go A5H2 for the 12.5, and probably an A5H0 for the 24 inch. They’re easy to swap out, so it’s not like it’s a big deal.

You could probably do an A5H0 for both, but you will have to choke the gas way down on the 12.5 to get it to run right, and it will probably be on the ragged edge of reliability, especially if it’s really dirty or if you run it when it’s extremely cold out. I don’t think you’d get away with the A5H2 on the 24 inch without short stroking or weak ejection.

Of course, I could be smoking crack with my predictions.

 

[MrDisaster]

You guys all realize he's not from Georgia(the state), right?

Yes, I'm from Georgia country

 

[MSTN]

Also consider the BCM MK2 recoil system. Much like the Vltor A5 recoil system, from the same designer as the Vltor A5 system, but with a new patented buffer design.

 

[Neurotic]

Also consider the BCM MK2 recoil system. Much like the Vltor A5 recoil system, from the same designer as the Vltor A5 system, but with a new patented buffer design.

What's different with the BCM buffers? Looks like the (internal) spring may be a different.

 

[MSTN]

Springs and buffer material.

 

[MontanaMan]

Gassing on a carbine length 12.5 and a rifle length 24 inch barrel are at the complete opposite ends of the spectrum.

My opinion: you will have issues if you buy one buffer weight and try to make it work for both. I would go A5H2 for the 12.5, and probably an A5H0 for the 24 inch. They’re easy to swap out, so it’s not like it’s a big deal.

You could probably do an A5H0 for both, but you will have to choke the gas way down on the 12.5 to get it to run right, and it will probably be on the ragged edge of reliability, especially if it’s really dirty or if you run it when it’s extremely cold out. I don’t think you’d get away with the A5H2 on the 24 inch without short stroking or weak ejection.

Of course, I could be smoking crack with my predictions.

Probably closer to truth than not.

MM