Here are three shot strings with the same setup as above, a stock 2240 with 14" barrel, RVA, and steel breech.... Pellets were as above, 14.3 gr. JSB Express, with three preload settings, 6 turns in from stock (just shy of coil bind), stock, and 2 turns out from stock (the minimum I can get with this adjuster).... I shot one shot every 30 seconds, and judging by the shot strings, that was a bit too fast, causing cooling that dropped the velocity and shot count.... One shot per minute would be better.... I also weighed the CO2 cartridges before and after and calculated the weight of CO2 in each....



Your brain can pretty much fill in the two strings I didn't shoot, at 4 and 2 turns in.... Counting all shots above 300 fps they would be about 38 and 43 shots, respectively.... There are a couple of interesting things to note.... At the maximum setting, the first half-dozen shots DID show a bit higher velocity, but they were accompanied by a spray of liquid CO2 that was very visible, as were the first 2-3 shots when the preload was set stock (not as much liquid, but noticable).... I think what is happening is that the dwell is long enough that when the cartridge is full, some of the liquid creeps along the sides of the piercing pin into the valve and is blown out the barrel.... It gives a small boost to the velocity, but is VERY wasteful of CO2.... Interestingly, when the preload was set 2 turns OUT from stock, the first shots didn't show that boost (or spray)....

At maximum preload, the velocity pretty much just keeps dropping with every shot.... After the first 8 shots, the velocity is LESS than what you would get with a stock setup, when shooting every 30 seconds.... On the other hand, with the preload 2 turns (1/8") out from stock, the velocity is much steadier, matching or exceeding the stock setting from shot 4 onwards.... I also calculated the average velocity, average and total FPE, and FPE from every gram of CO2, as follows....



There appears to ba a slight advantage to using maximum preload, but remember that it is a short string and the first few shots are extracting a bit of extra power from liquid CO2, so it's not as good as it looks.... One glance at the total FPE generated by a single CO2 cartridge really tells the story.... I'll make note of one thing here.... A few years ago I made a 1750 (.177 cal) with an 18" barrel, detuned it to stay right around 500 fps, with a short hammer stroke and light preload, so that the valve was self-regulating from 35*F to 75*F within about 30 fps.... It got over 140 shots totalling over 600 FPE, setting a record for the most FPE from a single CO2 cartridge that AFAIK, still stands today....

Hopefully this information will keep people from trying to get more power from a 22XX by leaning on the hammer spring.... I will say one thing, without a Chrony you would think you had a powerhouse by doing that.... The gun is much louder, and the CO2 spraying out gives the impression of more power.... The results from a short barrel will be even more disappointing....

Bob