AR Sponsor
Posted: 11/25/2025 1:53:14 PM EDT
| All Opinions welcome |
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this: https://www.vltor.com/shop/ar/stocks/aebk-a5-vltor-a5-stock-combo-kit/ what you want to know? i don't use the castl nut or the end plate or the buffer spring. i use the sprinco green spring, the bcm endplate, and the FCD a5 castle nut i lobe the stock, it is heavy and wish it had anti rotation on he QD cups. |
| I had one of the very first ones made about twenty years ago. Used a few of them over the years and ultimately a couple of years ago I went back to a standard Colt carbine spring and H or H2 buffer in everything because the A5 causes reliability issues where none exist. |
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Originally Posted By TheQuadfather: I had one of the very first ones made about twenty years ago. Used a few of them over the years and ultimately a couple of years ago I went back to a standard Colt carbine spring and H or H2 buffer in everything because the A5 causes reliability issues where none exist. What issues did you run into? Just curious. I have an 18" that kept having malfunctions with a carbine length tube, so I switched to the A5 system and it's been great ever since. |
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Originally Posted By Nobody69s: @TheQuadfather What issues did you run into? Just curious. I have an 18" that kept having malfunctions with a carbine length tube, so I switched to the A5 system and it's been great ever since. Originally Posted By Nobody69s: Originally Posted By TheQuadfather: I had one of the very first ones made about twenty years ago. Used a few of them over the years and ultimately a couple of years ago I went back to a standard Colt carbine spring and H or H2 buffer in everything because the A5 causes reliability issues where none exist. What issues did you run into? Just curious. I have an 18" that kept having malfunctions with a carbine length tube, so I switched to the A5 system and it's been great ever since. Failure to return to battery with G.I. mags. I had basically the same experience the military did when they tested the A5 and found it less reliable than the carbine-H6 setup, it just took me a few years to get the round count up high enough to recognize the problem. The problem did not present with Pmags and seemed to cease when I took the biasing spring out of the buffer but I quit the test shortly afterwards. Short version: If you want to run the A5 and ensure reliability, use Pmags, remove the biasing spring feom the buffer. Should be as good as the parts you replaced. 
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The A5, like anything else, is just a tool to be applied based on use case and performance requirements. Most issues with AR's are both caused, and solved, by buffer/gas system. Back 20 years ago when I was green on AR stuff, I'd just throw a part on, drop a loaded mag in and see what happens. If it runs, good to go. But now it's much more deliberate, I've realized there are a lot of variables in play and changing one requires proper data collection to understand results. So now I either have a spotter or camera setup on both the port door and brass ejection. When I'm setting something up I write brass ejection data down and chart it along with port size in barrel, gas system length, buffer and carrier weight, gas tube length, spring weight. All those things are interdependent. Personally I love the A5, it's another available tuning tool. But that doesn't mean it's right for every scenario. All my large frame carbines get one. Most of my SPR/DMR style small frames do as well. |
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Originally Posted By TheQuadfather: Failure to return to battery with G.I. mags. I had basically the same experience the military did when they tested the A5 and found it less reliable than the carbine-H6 setup, it just took me a few years to get the round count up high enough to recognize the problem. The problem did not present with Pmags and seemed to cease when I took the biasing spring out of the buffer but I quit the test shortly afterwards. Short version: If you want to run the A5 and ensure reliability, use Pmags, remove the biasing spring feom the buffer. Should be as good as the parts you replaced. We have 2 16" carbines set up with A5 tubes. They also have a Tubb flat wire buffer spring and RD5007 Kynshot buffer. One is an AA piston while the other DI. They've been running 100% with GI mags, about 2 thousand rounds. The DI has a AR10 tubb spring, but had to switch the piston upper to a std AR tubb spring to get it to function 100%. You might need new springs in your GI mags. I've also updated the followers. |
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Originally Posted By Blowout: We have 2 16" carbines set up with A5 tubes. They also have a Tubb flat wire buffer spring and RD5007 Kynshot buffer. One is an AA piston while the other DI. They've been running 100% with GI mags, about 2 thousand rounds. The DI has a AR10 tubb spring, but had to switch the piston upper to a std AR tubb spring to get it to function 100%. You might need new springs in your GI mags. I've also updated the followers. 2K rounds is not near enough to see if you have an issue. Those flatwire springs cause very erratic carrier velocity. You could get rid of the A5, the flat springs, and switch to Gen M3 Pmags and make your gun a helluva lot more reliable. Like, then you’d be running the same setup that the military has found to be the most reliable. |
Moderate-Length Barrel Evangelist
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Roughly same experience as Quadfather, across a couple lowers equipped with A5, a few uppers, a toughbox literally full of every duty-worthy mag imaginable, and 10s of thousands of dollars worth of ammo. I own a “training” company, and while these are set up for my own use, they occasionally get loaned out, so other users have also used them, and experienced “the problem”. Mine seem to only experience the problem when loading the first round from a mag. They don’t do it consistently, and have a greater tendency to do it on the first mag of the day. Brand or generation of mag doesn’t seem to matter. I’ve used 3 flavors of flatwire, and factory Colt rifle springs. I’ve implemented the removal of bias spring solution, but haven’t tested it enough to say for sure that it’s a fix. Cleaning and lubricating the guns was not a fix. I like the longer LOP the A5 provides, and believe it to be the only benefit. I’m no Vltor/BCM hater….I have a high opinion of them and use/recommend their products often. For the past couple years, I’ve been shooting gov’t furnished guns almost exclusively, with a regular carbine setup. No problems, just like before I ever used the A5. |
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Originally Posted By TheQuadfather: Failure to return to battery with G.I. mags. I had basically the same experience the military did when they tested the A5 and found it less reliable than the carbine-H6 setup, it just took me a few years to get the round count up high enough to recognize the problem. The problem did not present with Pmags and seemed to cease when I took the biasing spring out of the buffer but I quit the test shortly afterwards. Short version: If you want to run the A5 and ensure reliability, use Pmags, remove the biasing spring feom the buffer. Should be as good as the parts you replaced. I asked this in another thread but do you have links or news sources for those military tests? Everything I've seen says otherwise, so I really am curious if there's good quality conflicting info. |
| I don’t know if it’s online anywhere but the original test showed the A5 as slightly more reliable overall, but if you added up all the stoppages it only beat the carbine setup because they used clapped out guns and counted a couple of broken FCG parts as stoppages. |
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I just started using the BCM MK2 buffer on a 13.7 setup and never had a single issue while making it alot smoother .. But I only have about 700 rounds threw the setup but no complaints and would gladly buy it again.. Found this years ago from T-rex arms BUFFER SELECTION CHART |
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You mean an AR10 carbine buffer tube? And an AR15 rifle length spring? And the extra long carbine buffer with 4 wrights instead of 3 to make the bolt carrier have the same travel as the carbine and rifle recoil systems? Its fine if you need more mass than the H3 or rifle buffers. Other than that it accomplishes nothing the rifle or carbine system do. I used one with a buffer just a bit heavier than the standard rifle buffer to get the cyclic rate of an FRT build down to 600 rpm, while also allowing me to use a Magpul DT PR stock. There is nothing special about it. It was just a buffer length change to use the existing AR10 carbine receiver extension. |
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