help on AR rifle/carbine buffer..

grayingghost

January 11, 2015 11:36

I have Oly AR 5.56 rifle and a 9mm upper for it. The rifle has the standard A1 buttstock. When I mount the 9mm upper I have a collapsing stock I put on the Lower. The 9mm will run fine no matter which stock I use but the 5.56 will not function with the collapsing stock mounted. Both stocks have the correct spring and buffer. The malfunctions seem to be the classic 'short recoil' type. The buffer in the collapsing stock weighs 3 oz. I don't think they make a lighter one, think a heavier one might work. Either the bolt isn't going back far enough to pick up and properly feed the next round Or could it be going too fast, bouncing off the rear of the tube and coming foreward be fore the mag can feed??? I would think it gotta be either the spring or the buffer. I've tried 2 different springs from two different sourses.

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  1911builderMarine

  January 11, 2015 12:23

  There are 2 different buffer tube lengths for the AR 15. The rifle length buffer is longer than the carbine length buffer tube.
  
  Also different spring lengths ate buffer length/weights...
  
  Charles.

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  steve45

  January 11, 2015 14:33

  An Oly 9mm upper is a blowback system. The 5.56 is a gas system. If your 5.56 has fired a lot of ammo and especially if your using "dirty" ammo Wolf etc. you might have a blockage in your gas tube. They make a product that looks like a very long pipe cleaner that you can use to clean it.

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  Mobuck

  January 11, 2015 14:48

  Did the 5.56 upper EVER work right? If so, there may be a problem with fouling in the gas system. Another possibility is the screw holding the "A 1" stock to the buffer tube. If you use an "A 2" screw, it will reach through the threaded hole and stop the buffer before it travels fully to the rear. This seems to be the most likely problem as most people don't think about there being longer/shorter screws.

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  grayingghost

  January 12, 2015 05:36

  There seems to be a misunderstanding, sorry if I wasn't clear. When the 5.56 rifle is equiped with the A1 buttstock it runs flawlessly. It only malfunctions when I mount the collapsing stock. Could there be an incorrect buffer in the collapsing stock. I bought the stock with the 9mm upper. The buffer looks to me like the carbine buffer, the length is correct and the weight is 3oz. Could it be that I was sent a 9mm buffer, is there a difference? I see many buffers for sale in various weights but 3oz seems the lightest. As asked, could my problem be 'high speed recoil', might a heavier buffer work?

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  bigborefan

  January 12, 2015 11:27

  As a normal rule, the 9mm takes the heaviest buffer they make for an AR collapsible. The 3oz is generally the lightest and is meant for the 5.56.

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