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Posted: 10/2/2014 8:14:36 PM EDT
I am in the middle of building a new 308 build using the following
What buffer and buffer spring do I need to get to ensure proper cycling? |
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The heavier 5.4 oz H3 weight buffer is generally recommended for .308 AR's over the lighter 3.6 oz buffers. From what I can find, the LMT 308 buffer tube is a extended compared to the standard DPMS buffer tube. This would probably put it at around the same length (~7 5/8") as an Armalite buffer tube which means you should have no problem running a standard Armalite H3 buffer (EC0120) and an Armalite recoil spring (EA1095). If you can measure the length of your buffer tube I can give you a more definitive answer.
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Quoted:
I am in the middle of building a new 308 build using the following
What buffer and buffer spring do I need to get to ensure proper cycling? What is the port diameter on your CCMG RLGS 16" barrel? There is no standard buffer weight or length in the .308 AR market. There are some fundamental principles of putting a gun together, and when dealing with gas systems balancing out with recoil systems, you need to take into consideration several factors in order to end up with a functional gun: * Cartridge/ammunition to be used, which is the source of the gas * Gas system length * Gas port diameter * Steel gas block, not aluminum * Correct gas tube length and alignment with carrier key * Solid carrier key attachment * Correct dimensions on bolt carrier tunnel (there are at least 3 different ID's, the one that compresses the gas rings is the most critical) * Carrier weight * Buffer weight arrangement to balance out the cyclic rate driven by the gas system/cartridge * Recoil spring strength, composition, and length (incorrect recoil spring can result in spring coil impact, which will degrade the spring rapidly) The few companies that know how to take ownership of these factors make great rifles, namely KAC, LMT, Armalite, and JP. There are windows of reliability that you have to find yourself as a builder. Blanket recommendations from people are simply that, stabs in the dark. |
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My M5 Aero combo was a spontaneous purchase. I built three successful AR-15's prior. Figured the M5 would be just as easy. Man, was I in for a rude awakening. Thankfully this forum exists. I would have been totally lost and spent much more $$$ then what I did. I finished my rifle Friday of last week and got it scoped last night.I feel pretty confident I've done it right the first time. Won't know for sure until I hit the range.
I've read many times, the AR-308 is over gassed. So my only concern, I used a non adjustable gas block. On a 18", mid gas barrel. Paired with a JP Enterprise silent captured spring on the south end. Figured why buy one, if I might not need it. And if by chance I do, it's an easy enough swap and can use the existing on another build. |
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Since there is no standard on AR10's, some are gassed really well for a large segment of the ammunition market, whereas others are not. KAC has done a lot of engineering work to determine the optimum gas system length for the military loads intended to be used in their 16" carbines, and they went with RLGS.
I think much of the market in the AR10 world is driven by component availability and commonality, not much engineering analysis, if any at all. I think CLGS is a bad idea with .308 in the AR10. The first AR carbines were actually experimental AR10's, and the Dutch had some tool room prototypes to that end. They had what we would call a MLGS AR10 carbine, or maybe a gas system length between a CLGS and MLGS: 
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| Right now I am sitting at a rifle length gas system, with rifle length tube. I have not checked the size of the port but it's stock CMMG barrel. http://www.cmmginc.com/product_p/38dea7a.htm linked here. I'm just looking to get the most likely combination to put together and test fire it. |
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