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Posted: 11/9/2015 10:21:07 AM EDT
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Been on the forum for a while but haven't been lately Good to be back
Building my first AR and so far so good but I have questions regarding gas system compatibility. Is there a definitive source, text or guideline for matching up gas system components like system length, buffer weight, spring type, BCG weight, etc? I an trying to figure out what to expect at the first test and try to get it close to right on the first try. I know, no crystal ball. The setup I am considering is an 18" w/ rifle length gas system. I am stuck with a mil spec carbine length buffer tube because of a Thordsen stock and it came with a carbine buffer 2.9 oz, I also have a full weight BCG. I do not want to damage anything, first time out. Any help appreciated. |
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There are too many variables to predict what combination of parts will produce the optimum BCG velocity for a given weapon.
The barrel manufacturer may have a suggestion. A standard action spring and standard carbine buffer should work with anything; get too much spring and/or buffer weight and you may short stoke. You are not going to damage your weapon with what you have. I have an 18” RL gas system barrel that is not reliable with anything more than a standard strength CS spring and H buffer. I have another 18” ML gas system barrel that works great with a CS flatwire action spring and a H2 buffer. |
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Like PFC said, there are a lot of variables to consider. My practice is to start with "standard" setups, such as a carbine buffer and spring with 16" carbine- and midlength gas systems. Once upon a time, there were only a very few AR barrel makers, so things like gas port size were very consistent. Now, not so much. In fact, not all midlength ports are at the same distance from the chamber as all other midlength ports. You can find oddball barrels (and gas tubes!) now and then. My only middie is a Rock River, and I have bought a spare gas tube just to be sure I have one that will work.
Don't buy into all the chatter about "you have to have an H3 buffer with a carbine length gas system" or "the only way to go is with an adjustable gas block." Absolutes like those are usually based on very small sample sizes (like ONE) and often reflect a member's limited knowledge base. The AR design will work fine with too much gas, a wimpy action spring, a half-clogged gas tube and worn out gas rings. You can make an AR work better and more reliably by starting with known-good designs, such as the way I described my practice above. |
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