120 grns is a little more than I care to shoot and as mentioned above would keep the pressure at or below BP pressures (15,000 to 25,000 psi). The self cocking is exactly one of the issues that frightens me, I would not want a get of high pressue hot gasses venting near my face!
The 120 grns was during load development long time ago. Wasn't a load I shot regularly. I often used self cocking as a sign I was maxed out on my sidelocks and would back down from there. I just mentioned it because it is a sign of how much gas can blow back through that tiny hole.
