Originally Posted by RobF
The hammer moves barely a few mm... as much as i'm loathed to contradict Pete, I think you're feeling the air leaking past the valve stem. I've taken mine off and just taped over it. There's not enough pressure to blow the tape off. And any debris finding it's way into that area stands a good chance of being stuck to the tape. Plus it's one less thing to go wrong, or let water etc in...
I'm guessing the leak % is fairly consistent. As you say, free consistent movement is key
I didn't say it was only caused by the hammer but when I tested it on mine, without any air in the reg, air can still be felt coming from the dry fire button due to the hammer displacing the air in front of it...don't forget that the hammer moves further than you see when cocking the rifle as it has to knock open the valve.
I'd suspect that the air moved would be lower on an older rifle as things have worn more but it would be interesting to see if the power goes up slightly if you removed the piece of tape you've used.