Upper won't cycle...

[PTK]

I'm using a M1S upper, checked and made sure about the gas port, it measures 0.104", the gas tube is good, using a collapsible stock and "carbine" buffer, using 15.4 gr of R7 and a 220gr SMK HP bullet, and 12.4gr of H110 and the same bullet. Neither cycles the action, though the H110 ejects the case further. What am I doing wrong?

[GaryM]

Remove the internal weights from the buffer and see if that works. If it still doesn't eject try clipping coils off the buffer spring one at a time until you get it going.
That is what it took for me.


To remove buffer weights simply knock out the roll pin, pull the plastic end piece out and the weighs will just fall out.

[Pitt300]

Are you using a can?
These should be supersonic loads?
What mags are you using?

[Pitt300]

Call Paul @ M1S. 903-546-2087
He has a special CAR spring & lightweight buffer that he says will cycle subs.
Do not use w/supers.
Supposedly you do not want to start cutting down springs because of how they can react when their flat based portion is removed.
I use a full size stock w/CAR buffer but I can see where the short stock would increase spring tension.
His Whisper CAR buffer is even lighter than a regular CAR buffer.