Posted: 10/18/2013 12:22:21 PM EDT
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hey all building an ar15 from the ground up i just bought a magpul ubr stock for im running 14.5" barrel gas piston cos i want something different. what buffer do i need and what is the difference in the buffers from light heavy hydraulic what do they actually do ?
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Try starting with a H buffer.
The different weights resist the impulse of teh BCG, slowing down unlocking and cycling. too light and your rifle beats itself up. Too heavy, and you have cycling issues. However, your gas port and ammo also effects things, so there's no magic buffer weight that you "must have". |
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I run a carbine weight buffer on my 16", before that it was a full length rifle A2, since it was ban-era.
H or Carbine will probably run fine in a 14.5". Besides the gas pressure and distance down the barrel the gas port is, and the ammo you're firing, the other issue is how far the buffer has to travel in the tube. The shorter the buffer tube/receiver extension is, the more "work" the buffer needs to do in a shorter space and time, so it needs to be heavier for that as well. For instance, I'm using my leftover A2 rifle length buffer tube on my 7" pistol build to give me a longer LOP for one of those Sig Sauer arm brace thingys. Even though it's only a 7", since the rifle length buffer tube has a few more inches of distance and the longer spring with more coils in which to do it's thing it might work fine. If not, I'll try an H buffer etc. Hell, I bet even the amount of air in the buffer acts like a spring to a degree, depending on the length and how big the vent hole port at the end of the buffer tube is, and how much the stock design lets some air out. As mentioned, how hot the ammo is, bullet weight, gas port diameter if it's a bit off spec, lubricity of the bolt and BCG like if it's parked, in the white, or has a fancy nickel-kryptonite coating, everything gets to add a little input into how it cycles. Lots of variables and an almost infinite number of outcomes, however fortunately there's only three main choices in buffer weights, well, maybe four if you count some of those extra heavy 9mm blowback buffers. Hydraulics are expensive, and one hell of a mess when they fail. 
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| So i have a DPMS 20" gun running a carbine buffer normally it puts brass out at 3 O'clock but when i suppress it it dam near puts brass ot at 1 O'clock should i switch to a heavy buffer and will i have to change my tube? Or is it ok to leave everything the way it is? |
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I don't think it'll hurt, but there's lots of factors that affect ejection patterns besides just over/under gassing and bolt velocity. Funky torque on the barrel nut, slight misalignment of the barrel/barrel extension making them not 100% concentric or at least parallel in the X and Y planes with the interior bolt raceway of the upper, extractor tension being too high, ammunition case head variances, and the strength of the buffer spring... All of that can effect ejection patterns and ejection distance above and beyond gas and buffer weight. Personally, unless I saw signs of excessive wear I would not really worry. |
