CorpsTex

Clearly stated in my first response the both AR10 builds are rifle length not carbine length builds. Check with Wing Tactical they carry all buffer length in both Carbine length and Rifle length, 2.5" carbine and 5.3" for rifle length. He can only fix his own problem with a little time of web searching for the correct parts for his AR to function correctly. Without any body else's input.

Clearly stated in my first response the both AR10 builds are rifle length not carbine length builds.

Better check with Aero Precision, they sell the correct buffer, buffer spring and buffer tube for a rifle length AR10. This will allow the correct bolt hold back when the magazine is empty. And yes the overall buffer length is between 5.3 to 5.5" long for proper bolt operation

Your buffer is too long, I have a few AR10's. The correct overall length of your buffer should be 5.300 inches. With a overall spring length of 12.5". I encounter the same problem during my second build. Bolt carrier would not properly latch on the bolt catch. These builds are both rifle length builds not carbine with Magpul full length rifle stocks with extended recoil pads attached.