Phantom not shooting on a fresh 12g

[Memornix]

I am new to phantoms and just picked one up second hand. Put a fresh 12g in it and it would cock but when the firing, the hammer hits the valve but all I get is a little pop. I have experienced this before with markers running too high of a pressure so I burped a little air out of the 12g and she fires fine at a reasonable velocity.

Thoughts on getting this thing to shoot on a fresh 12g. I have not had this problem with my Trracer, Buzzard or any other nelson based marker before so i am kind of at a loss.

[Axel]

Sounds to me like the previous owner tried tuning it for low pressure, and the high pressure from CO2 is keeping the valve shut.

I would check the valve and main springs, and try swapping them with fresh stock springs if you have a pair. Also check for dirt or anything impeding movement of the hammer, or any other non-stock tweaks you see inside. Check all the seals and give it a good cleaning while you're in there.

[Axel]

Or, just thinking it out, maybe the TPC is unthreaded out of the bolt. That's the "Tuned Port Compensator" that you adjust down the barrel with a special tool to tune velocity (or take the barrel off and use a screwdriver)

I'm not sure if that would cause the problems you're experiencing but it is possible to over-adjust the TPC

[Memornix]

Yeah, it is definitely a too much pressure on the valve issue. I have not opened the valve to check the spring yet, but that is my next place to go. Just curious if there was some weird phantom kung foo I didn't know about.

I did adjust the velocity on the bolt after I burped the 12g and got it shooting 280s so I don't think that is the issue