Normal leak down

Nope. PCPs shouldn't leak.

Note that when you fill them up, the air gets warm and you'll have less showing on the gauge after it cools down, but not 1000fps less.
Thanks for the reply. Took my time with the MK5 pump so not much heat. Doing the ballon test on the muzzle and will go back over all the “make sure these are tight” connections.

OFG