For AR-15 PCC guns with barrel lengths of less than 8”, we recommend our standard damped buffer/spring combination with our standard damped 9mm hydraulic buffer (Part# RB5007) and the SPRINCO Extra Power AR-15 carbine buffer spring (color code RED – Part# SPRINCO-25004).  5.5" barrels have become the most common in the short barreled AR 9mm arena and this combo has worked very well for our customers with those.  If your barrel is even shorter than that, then you will probably need to do some trial and error with which buffer spring you need.  But the RB5007 standard 9mm buffer will still be the buffer of choice.  

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