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Posted: 1/10/2012 6:32:51 AM EDT
| I just got my 9mm AR finished and had a couple of questions. Is the main reason for using a 9mm buffer and heavy spring to make it more reliable or something else. I just put in a standard spring and buffer that came with my Magpul stock. In limited testing (very limited) I have not had any failures to feed or eject. I have a Wolf extra power buffer spring I got in trade but have not put it in. All testing has been done with just 115gr NATO ball so far. The rifle is a Spikes 9mm upper on a DDLE 9mm lower. What say you all? |
| The reason that a heavy buffer and spring are used is that the 9mm is a blowback system...not a gas one. It's used to slow down the BCG so it doesn't beat itself to death. It's the same reason that the BCG on a 9mm is much heavier than a standard one. It'll work with the standard carbine buffer/spring, but you and your rifle are taking a beating that neither should have to. I'd swap to the recommended spring and buffer. |
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Quoted:
The reason that a heavy buffer and spring are used is that the 9mm is a blowback system...not a gas one. It's used to slow down the BCG so it doesn't beat itself to death. It's the same reason that the BCG on a 9mm is much heavier than a standard one. It'll work with the standard carbine buffer/spring, but you and your rifle are taking a beating that neither should have to. I'd swap to the recommended spring and buffer. Not quite... The reason for the weight/mass of the BCG/buffer is to keep the chamber closed until the pressure from the fired round is reduced to a reasonable level. The side effect of more or less mass in the BCG/buffer is that it can make the action cycle slower or faster and affect the cyclic rate in FA. However, the difference between running a std carbine buffer that weighs ~3 oz instead of a std. 9mm or H3 buffer that weighs ~5 oz, isn't going to result in the gun beating itself to death that much sooner... |
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you may as well get the buffer spacer also unless you got a long buffer liek the hahn. or you can put a stack of quarters in the buffer tube behind your spring. this will limit how far back the buffer goes in the buffer tube. since the buffer is standard length, but 9mm is half the length of 5.56 you buffer is traveling like 1.25" farther back than it needs to which is putting unwanted stress on your bolt hold open and recoil.
my setup is the vltor a5h4 buffer which is 7 oz IIRC and rifle length wolff spring in a carbine length buffer tube. it is just about the perfect setup. the a5h4 buffer is longer and clears the mag just enough to strip off the next round and chamber it. recoil is NOTHING!! now. feels like my .22. |
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I just got in a Spikes ST-9x buffer and installed it with the Wolf spring. Hopefully I will get out next week to test it. Now to start shopping for some optics for it. I am leaning towards an Aimpoint. Any thoughts? Let us know how that buffer and spring work out. As far as optics goes I've always been happy with my Primary Arms optics. I think any non-magnified red dot sight on a 9mm carbine would be ideal. |
| My 10.5" SBR runs fine with a standard buffer and spring, but that's with vanilla 9mm loads-124s and 115s at conservative, over-the-counter velocities. Were I to start messing with other loads, I might have need to put in the heavier, 9mm buffer. As said above, if it runs, don't mess with it. If it gives you problems, then you might need to think about buffers and springs. |
| I ran a Spikes 9mm buffer and normal carbine spring yesterday on a 10.5'' upper and it ran great (except for the disconnector pin walking out, that was fun). Once the LPK comes tho its going on a lower with a vltor a5 tube, wolf extra power spring and the 9mm buffer w/ a spacer, probably reduce felt recoil even more. |
| You could use whatever you want for a spacer, but you should try quarters first to figure out the best length. The quarters are pretty much a perfect fit in the buffer tube and you can easily add or remove to get the desired function and reliability. Then measure how many you used and make a spacer. |
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Install that spacer.. doesn't matter what it is as long as it's right size and doesn't interfere with the buffer/buffer spring. I just made mine from aluminum and made it similar size as the buffer so it would fit in the spring like the buffer.
You need that spacer to help prevent damage to your bolt catch. I broke my bolt catch when it slammed into it. I was using a regular buffer spring (I think) and a Spike's ST-T2 heavy buffer (regular heavy AR buffer) |
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