Predictably, the very short hammer travel translated to fairly low fill pressure. Even at 2500 psi, the velocity was in the 600s. At about 2200psi or 150 bar, it started shooting in the high 770s. I started my string of shots there, using the JSB Express .22 at 14.3 gr. The velocity quickly rose to 800 fps by the end of the first 10 shot string. Was shooting 820 fps by the end of 20 shots and peaked at 829.4 fps on the 25th shot. Down to 826 by the 30th shot and 804 by the 40th. The 50th shot was at 779.2 fps, so I ended it there.
The overall average for the 50 shots was 807 fps and the extreme spread was 51.9 fps. For field target I would cut 10 shots off each end of the string to lower the spread (25 fps ES for 30 shots), but for hunting and plinking, the 50 shots will all be very usable.
My next move will be to decrease the size of the port to restrict the amount of air getting through. I will lengthen the hammer stroke as well, which I hope will flatten out the trajectory some and also allow me to fill to a higher pressure level, resulting in more usable shots. My S400 seems to like the combination of a small port and hard hammer strike, so I'll see if it works here as well.
A regulator set at about 1800 psi would presently give me a big long string at about 825 fps. Not ready for that yet, as I would like to get the peak velocity down some, get the max fill up higher and the number of usable shots increased. I may tune for just under 20 ft/lb to make it usable at the Port Club and still have lots of power for hunting.
It certainly is fun messing with this gun. Snowing hard right now so these indoor activities will have to do for now. Looking forward to getting out to see what it will do at 50 to 55 yards. Now to get that new port made up. I may get a variety of sizes and settle for the one that yields the best performance according to my way of thinking.
Be back later.
Tim
