Secret sauce to the barrel length/gas block/buffer weight equation?

[Indianapail]

I have built a few ARs and I always get hung up on what buffer to run with what barrel lengths and gas blocks.

Apart from trying all the buffer weights at the range or just running adjustable gas to dial in, how does one know what buffer to run?

 

[Sigblitz]

Barrel length and gas system? It's all about the bayonet. The Stoner 20 inch was put where a bayonet will mount. Then came the Carr 15, with no room for a bayonet. So the barrel was lengthened to 14 1/5 to accommodate one. The gas system on the civilian 16 inch was moved forward from the 14 1/2 for, you guessed it, the bayonet.

 

[Squid556]

Buffers:
Under normal conditions just stick to standard weight (3 oz) carbine buffers with most builds. Short barrels under 13.7 likely will benefit from heavier buffers. Several manufacturers ship AR pistols with H2 or H3 buffers.

9mm is a totally different animal and needs special considerations to make sure it runs properly.

Rifle length and weight (5oz) buffer systems are normally seen on longer (18+) barrel configurations although they may also work on shorter systems. Because of their weight they may cause short stroking in cold weather with 18” rifle and 14.5” mid

Gas Systems:
-Rifle length gas 18-24 inch barrels. Carbine and Rifle buffers seen

-Mid length gas 14.5 - 18 inch barrels. Carbine buffer systems usually seen with these.

-Carbine gas 10.5 - 16 inch barrels. Carbine buffers here too. Sometimes these guys will benefit from an H1 buffers.

-Pistol gas anything under 10.5 with the exception of some 300 blk 16 inch barrels. Carbine buffers. Often times with heavier buffers as well.

Adjustable gas blocks usually just with suppressed use and/ or abnormally light BCGs I’ve never needed one personally.

Learning to read ejection patterns is going to help any issues. This might help as well

AR-15 Buffers Explained by Small Arms Solutions LLC -

Chris Bartocci of Small Arms Solutions LLC has released a video, where he reviews the different types of AR-15 buffers. He discusses the evolution of the buffers in chronological order.

www.thefirearmblog.com

 

[Sigblitz]

/\
Very good video in that link.
From the video, h2 and h3 buffers come into play with select fire. They act like a dead blow hammer to stop buffer bounce.
When the bolt bounces on a weak buffer, returns forward, and locks into battery, it still wants to bounce back, causing light strikes on the firing pin.

He said the standard h buffer is fine for semi automatic, but h1 is preferred.
One take away I got was the original edgewater buffer with no weights was fine for 700 rounds a minute, until the charge rate of the ammo was increased.
I had an ar with the h buffer that was light striking on 75 grain, so the standard h buffer wasn't optimal. I don't remember the twist rate, so it could have been too heavy for my barrel. But looking back, it would have been fine with an h1 buffer.

 

[Kirk Freeman]

More on A5:

 

[Sigblitz]

I see the spring inside the a5 buffer as a negative, not allowing the weights to move forward to stop buffer bounce when it locks into battery. They added mass to the a5, which would mitigate this, so it cancels out.

But when the charge rate drops in cold weather, the a5 may be too heavy.

 

[Indianapail]

Buffers:
Under normal conditions just stick to standard weight (3 oz) carbine buffers with most builds. Short barrels under 13.7 likely will benefit from heavier buffers. Several manufacturers ship AR pistols with H2 or H3 buffers.

9mm is a totally different animal and needs special considerations to make sure it runs properly.

Rifle length and weight (5oz) buffer systems are normally seen on longer (18+) barrel configurations although they may also work on shorter systems. Because of their weight they may cause short stroking in cold weather with 18” rifle and 14.5” mid

Gas Systems:
-Rifle length gas 18-24 inch barrels. Carbine and Rifle buffers seen

-Mid length gas 14.5 - 18 inch barrels. Carbine buffer systems usually seen with these.

-Carbine gas 10.5 - 16 inch barrels. Carbine buffers here too. Sometimes these guys will benefit from an H1 buffers.

-Pistol gas anything under 10.5 with the exception of some 300 blk 16 inch barrels. Carbine buffers. Often times with heavier buffers as well.

Adjustable gas blocks usually just with suppressed use and/ or abnormally light BCGs I’ve never needed one personally.

Learning to read ejection patterns is going to help any issues. This might help as well

AR-15 Buffers Explained by Small Arms Solutions LLC -

Chris Bartocci of Small Arms Solutions LLC has released a video, where he reviews the different types of AR-15 buffers. He discusses the evolution of the buffers in chronological order.

www.thefirearmblog.com

This really helps clear up the confusion, I appreciate the response.

Also means that my current A5 H2 13.7 middy may face some issues in cold weather. Although it may be G2G with a can.

 

[worddoer]

Buffers:
Under normal conditions just stick to standard weight (3 oz) carbine buffers with most builds. Short barrels under 13.7 likely will benefit from heavier buffers. Several manufacturers ship AR pistols with H2 or H3 buffers.

9mm is a totally different animal and needs special considerations to make sure it runs properly.

Rifle length and weight (5oz) buffer systems are normally seen on longer (18+) barrel configurations although they may also work on shorter systems. Because of their weight they may cause short stroking in cold weather with 18” rifle and 14.5” mid

Gas Systems:
-Rifle length gas 18-24 inch barrels. Carbine and Rifle buffers seen

-Mid length gas 14.5 - 18 inch barrels. Carbine buffer systems usually seen with these.

-Carbine gas 10.5 - 16 inch barrels. Carbine buffers here too. Sometimes these guys will benefit from an H1 buffers.

-Pistol gas anything under 10.5 with the exception of some 300 blk 16 inch barrels. Carbine buffers. Often times with heavier buffers as well.

Adjustable gas blocks usually just with suppressed use and/ or abnormally light BCGs I’ve never needed one personally.

Learning to read ejection patterns is going to help any issues. This might help as well

AR-15 Buffers Explained by Small Arms Solutions LLC -

Chris Bartocci of Small Arms Solutions LLC has released a video, where he reviews the different types of AR-15 buffers. He discusses the evolution of the buffers in chronological order.

www.thefirearmblog.com

I believe the truth can only be found out once you sacrifice a rubber chicken while chanting "oh what a goose I am" while wearing one of the outfits from the village people!

OR

What he said^^^^^^^^^^^^^^^^^

 

[Squid556]

Hey thanks for the good feedback folks.

Something I forgot to summarize was that a lot of buffer development / changes was to increase reliability with automatic operation. Seems one of you beat me to that.

Semi auto guys dont really find the same issues. Unless you dip into buffers too heavy for the amount of gas given. Then its just short stroking issues which are easily fixed.

Only other buffer / spring issues you may find are people with binary triggers. They live in that middle ground where a system has to be perfecly balanced kinda like the auto guys. I've known several people have to swap parts to get those binary jobs running smooth.

Also here is what I was referring to with learning to read ejection. I should have included it with my first response but felt I was already going too long.

 

[Lodge]

I went with an A5 standard weight system in the new build.
16" barrel with mid length gas.
Superlative Arms adjustable block.
Brownells low mass BCG.
Radian Raptor SD charge handle.

Shooting 55 grain 5.56. Ejection at 4:00.
Smooth Shooting.