A few notes on the Teflon (PTFE) seal.
Arriving in guns in the early 80s it was something of a new wonder material compared to the leather seals of the time. Lowest known coefficient of friction even to this day...non drying and machined up in 5 minutes....it seemed ideal and advocated by Beeman and Bowkett.
However, its not so great in the UK, with our vastly fluctuating temperature between a few degrees, 20 degrees and - degrees...because PTFE is temp sensitive. That bad that i often ran with 2 separate zeros. One for an average 15 degree day and one when freezing....It maybe worth noting at this point that you may not have this problem depending where you are State side, and where I cannot imagine anywhere would be as bad as here....Also, we are talking pistol here, where differences will be in the range 20 to 30 fps difference, not 60 fps as with the FWB sport rifle.
Notes for improvement...One thing that improves this issue, is polishing the seal face down until the barest of slip fit. This way any increase in diameter due to temp expansion, slows the gun much less than it might, while shrinkage, has the lesser impact....(this is noted by any seals in any guns which have worn to the point that they barely seal, but still make surprisingly good power but a tight seal can play real havoc with the guns power) ...nice slip fit then...
Notes on piston weighting. The OEM guide turned the wrong around to be inside the piston can give you 25 grams added weight to the piston, and send the Hobby pellet into 570 fps territory... Placed in at the opposite end (no weight in piston) loses 40 fps as the piston weight fights the long TP on its own.....its not the heaviest piston, being relieved for the duel cocking arm slots.....it needs the weight..
Finally, polish your barrels. HW in their wisdom put a lot of lube into the 45 and a used purchase can have loads added by uniformed shooters....It eventually gets up the barrel and plays havoc with accuracy. Use some proprietary firearm bore cleaner like Youngs 303, or a Napier bore cleaning kit and keep going until it comes up mirror finish..It pays big dividends..