The on-off pin remains inside of the small on-off top oring sealing the air passage until the sear can actually rotate forward. The sear can only rotate forward if the bolt is fully back in the reset position. Its not the pin that is causing leaking out the front in a pump mag anyway. Its the exposed vent hole. Normally there is residual pressure in the front chamber when the bolt resets. If the vent hole is exposed, that air is allowed to escape, so its wasted.
Originally Posted by GoatBoy
The vent distance doesn't affect the operation of the level 10 for anti-chop. The vent distance only affects how far forward the bolt needs to be before it can vent the excess air out of the chamber so that the bolt spring can push it back to the reset position. In a pump mag, the wave spring would hold the bolt forward causing the vent hole to be permanently exposed which would allow it to vent all residual air out of the chamber.
The level 10 will work for a pump mag as it normally does for any mag. The secret to get it to work without leaking air is too allow the carrier oring to sit far enough forward so that it is always in front of the vent hole. We don't need the vent hole for a pump mag since you are manually resetting the bolt anyway, so you don't need the spring force to be larger than the residual chamber pressure force. If you have a spare powertube tip, file it down to allow the carrier to sit farther forward. Flipping the carrier won't work, because the oring can be pushed forward out of the carrier.
Except for the Automag in front, its usually the man behind the equipment that counts.