Rifle gas system + telestock = ? buffer/spring

[Mj0lnir]

Hi gents; recently ordered a 20" rifle from CMMG, but at the last moment changed the A2 stock to a telestock.

Didn't realize it at the time, that this changes the buffer/spring. (That's what I get for reading all the great info on this site...and yes, I'm a rookie to AR15s).

So, to keep the telestock, what spring/buffer do I need to change to to get reliable operation?

Thanks in advance.

[welchtactical]

I've been running a wolff extra power spring and a H2 buffer with great results in my rifles. I only use the Wolff spring because I use my lowers with piston uppers too but works with regular uppers great too, not to say a standard spring wouldn't.

[Robb Jensen]

A rifle length gas 20" will run just fine with a standard CAR 2.9oz buffer and standard rate CAR action/buffer spring.

[KevinB]

The Canadian Forces found that the H2 buffer was the most relibale weight over the barrel spectrum - and issue it on all lowers equipt with telestocks from 10" to 20"

[Mj0lnir]

All interesting info; so I'm guessing standard through H2 buffers work fine because the carbine spring has a higher rate than the rifle spring?

[sgtlmj]

You'll be amazed at how smooth the rifle-length gas system runs with that setup. It's like butter.

[Robb Jensen]

The Canadian Forces found that the H2 buffer was the most relibale weight over the barrel spectrum - and issue it on all lowers equipt with telestocks from 10" to 20"

I find it interesting that they went that heavy. Heavier than CAR is to slow the bolt on a CAR gas length system. Rifle length doesn't need the slowing. I'm betting they went with much larger gas ports on the 20" barrels to be reliable with that heavy of a buffer. I've run a H2 and a H3 in a lower with a FN 20" barrel and with XM193.....I could tell that it was quite a bit weaker bolt velocity wise than with a rifle buffer/stock. Recoil feels like very weak ammo which XM193 is not.

I'd like to see a comparison of the gas port size on a US made Colt and FN 20" barrel vs the C7A2 barrel gas ports. I'm betting the C7A2 has much larger gas ports.

[KevinB]

The C7A2 upper is interchangeable with the C7 or C7A1 -- no change to the barrel -- same gas port as the M16A2/A4

[Trim2L]

I find it interesting that they went that heavy. Heavier than CAR is to slow the bolt on a CAR gas length system. Rifle length doesn't need the slowing. I'm betting they went with much larger gas ports on the 20" barrels to be reliable with that heavy of a buffer. I've run a H2 and a H3 in a lower with a FN 20" barrel and with XM193.....I could tell that it was quite a bit weaker bolt velocity wise than with a rifle buffer/stock. Recoil feels like very weak ammo which XM193 is not.

I'd like to see a comparison of the gas port size on a US made Colt and FN 20" barrel vs the C7A2 barrel gas ports. I'm betting the C7A2 has much larger gas ports.

Buffer weights:

CAR buffer 2.96oz
CMT H2 buffer 4.57oz
CMT H3 buffer 5.43oz
Enidine CAR buffer 4.34oz (newest type, softer spring rate)
Rifle length buffer 5.2oz
9mm steel buffer 5.6oz
Colt X buffer 7.9oz

The H2 buffer is lighter than the Rifle buffer. If anything with an H2 buffer on a 20" M16 the bolt and carrier should run at a slightly higher velocity than with a rifle buffer.

[Robb Jensen]

The H2 buffer is lighter than the Rifle buffer. If anything with an H2 buffer on a 20" M16 the bolt and carrier should run at a slightly higher velocity than with a rifle buffer.

Very true but that's only part of the equation. The buffer springs are different as well.