RE: .22 RW HP Chronograph Results with JSB Monsters and a blown breech seal; all in a day
In brief, 50 shots between 49.92 ft/lbs and 50.74 ft/lbs. Also, the 50 shots in five 10 shot strings averaged 941 FPS, 949 FPS, 949 FPS, 947 FPS and 945 FPS respectively. Last, best FPS (average) and ft/lbs over 50 occurred between 242 BAR and 191 BAR.
Details shown below. Your mileage may vary.
FYI - Bbuna oring breech seal blew out shortly after recording above data. I changed out the oring with another buna. Pellets subsequently fed roughly with more than normal resistance into chamber, groups started looking like bird shot, and a five shot string averaged 931 FPS with over 220 BAR in the gun.
It couldn't be the breech seal, could it?
Yes it was. REplaced oring with another buna once I got home. Pellets started feeding smoothly again with less effort and velocity started averaging 950ish again.
Note I replaced the viton breech seal with buna a few days back because I was told that groups opened up with viton. I have not yet checked this out with my gun yet, but will.
Best wishes
The other Mark B.