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cakesterkiller 01-06-2013 12:55 AM

i just got an A2 solid stock in a trade and was just about to install it when I noticed the buffer was heavier than the one that came out of my m4 style... what does the different weights do? its a 16 inch upper with carbine length gas tube if that's info ya need

Quentin 01-06-2013 01:48 AM

Rifle buffers are heavier than carbine buffers, even the H3 carbine buffer. A rifle stock kit will work fine on a carbine upper.

Jpyle 01-06-2013 01:57 AM


Originally Posted by Quentin
Rifle buffers are heavier than carbine buffers, even the H3 carbine buffer. A rifle stock kit will work fine on a carbine upper.

True that...I run a 16" carbine upper on a rifle length buffer and ACE skeleton stock, no cycling issues to date.

Quentin 01-06-2013 04:42 AM

And I used to run an A2 stock kit on a 16" midlength with no cycling issues.

kbd512 01-06-2013 09:47 AM

If you are going to run a rifle stock on your carbine, just make sure you use a rifle buffer spring versus a carbine buffer spring.

kbd512 01-06-2013 11:20 PM

I realized that I incompletely answered the question, so I will provide some amplifying information.

1. All direct impingement guns have an optimal gas tube length to barrel length ratio, if you will, that determines how smoothly the system cycles and the optimal length of barrel, from extensive government and private testing, has been determined to be approximately 4 inches of remaining barrel in front of the gas port. Now, gas pressure, gas port location and size, and bullet velocity all play a part in determining how the gas system functions, but "dwell time" is the most important factor (given a properly sized gas port) with SAAMI .223 or NATO 5.56MM spec ammunition with bullet weights between 55 and 77 grains. The term "dwell time" refers to the amount of time after which the bullet and gases have passed in front of the gas port during firing after which time the bullet has still not left the barrel. The dwell time is typically measured in milliseconds and you can google the topic if you are really interested.

2. The original AR15 rifles with a 20 inch barrel had an optimal 4 inches of barrel in front of the gas port.

3. The original AR15 carbines with a 14.5 inch barrel also had an optimal 4 inches of barrel in front of the gas port.

4. The civilian AR15 carbines with a 16 inch barrel have an extra 1.5 inches of barrel in front of the gas port.

This is the reason why buffer weight, buffer spring weight and rate, and ammunition selection are so critical in civilian carbines. The cyclic rate, something that actually refers to the speed with which the gas system operates at versus how many rounds per minute a particular weapon can fire, is higher in a civilian carbine. The cyclic rate is actually higher in all carbines than rifles because the pressure of the gas behind the bullet is higher because the gas is tapped off to operate the gas system closer to the chamber of a carbine than a rifle. The reason the pistols and really short SBR's sometimes have cycling problems is that there is not enough dwell time or time for pressure to build in the gas system before the bullet has left the barrel.

5. Finally, we arrive at the "fixes" to get AR carbine length gas systems with 16 inch barrels to behave like carbine length gas systems with 14.5 inch barrels.

You can keep the bolt locked longer in a civilian carbine using heavier buffer springs and/or heavier buffer weights. This reduces the cyclic speed of the bolt, prevents premature unlocking of the bolt, and reduces the resultant beating that the bolt takes from a high cyclic rate.

The following are common buffer "weights", if you will, for carbines:

Standard carbine buffer - ~3 ounces
"H" carbine buffer - ~3.8 ounces
"H2" carbine buffer - ~4.6 ounces
"H3" carbine buffer - ~5.4 ounces

If your carbine functions properly with a given buffer weight, then there is no real need to use a heavier buffer. For example, my Colt 6520/6720 has a "H" buffer and functions reliably with Federal 55 grain XM193 ammunition. I could experiment with the heavier buffers, but it never fails to function and doesn't damage the brass, so I do not see the need to mess with it. If I were inclined to shoot heavier stuff or hotter stuff and I saw lots of markings on the rim of my brass from the extractor, ripped/bulged/otherwise damaged cartridge cases, then I'd be inclined to purchase the "H2" and "H3" buffers from Colt and determine which one permitted the smoothest function for my carbine.

Hope that helps

purehavoc 01-06-2013 11:54 PM

I have played around with pouring my own lead for my buffers , it gets frustrating some times . I had 2 identical rifles one runs a 4.2 oz buffer perfectly the other will only run a 3.8 oz , It runs fine with the heavy buffer it just wont lock the bolt open on one gun . Sometimes it just good enough to use the factory 3.0 oz carbine buffer. I look at it like this , if there isnt a problem dont try to fix it and create a problem

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