AR-9 Carbine FTE Issue

[LongJohn53]

I built an AR-9 Carbine using a Spike's Tactical lower that takes Colt Mags. I'm having failure to eject issues pretty much routinely - stove pipe or caught between the bolt straight in against the face of the receiver concurrent with a new round being fed. Current configuration consists of a standard carbine spring and Spike's T3 buffer with a spacer at the end of spring. The bolt is manufactured to run with either Colt or Glock magazines. I've also run a Colt Only bolt and had the same issues. I've tried adjusting the position/alignment of the ejector with some temporary relief from the FTE but it reoccurs. Any suggestions of spring/buffer weight combinations or other thoughts to help resolve the FTE issue would be greatly appreciated. Many thanks!

 

[shrxfn]

When I built my Glock mag AR9 I used a 9mm specific buffer and spring set. I can't remember who I got it from probably Primary Arms or PSA but it has run flawlessly for hundreds of rounds. I looked and 9mm buffer is almost 6oz and T3 is like 5.4oz so missing a little weight. Hope this helps.

 

[LongJohn53]

Thanks for the feedback. So as not to have all my eggs in one basket, I also have a AR9 build lower that uses Glock magazines and it runs perfectly with a 8.9 oz buffer. So, I think you're right about missing some weight. One thing I've noticed about the Colt lower is the ejector arm does not appear to be as robust as that in the Glock lower and will probably require some periodic adjustment to maintain ejection performance. Attached photo shows Glock ejector on left and Colt ejector on right.