Edgun R3 .22: Shot String, Air Efficiency, & Trigger

I have a great interest in Cricket’s shot string and air consumption. Based on Sherrod’s string data posted on “.22 Cricket Chrony String” several days ago (http://talonairgun.com/forum/viewtopic.php?p=251160&sid=09baa4baf5f92ecbee428a192beb618d#251160), I plotted it out against one of my recent Matador strings. I also compared their air consumption. I apologize if I make any mistake on his writing.:oops:

I dropped last 6 shots of the Cricket string to obtain the mean velocity and ft-lb energy. I used those mean values for air consumption calculation (220 to 110 bars for Cricket with 280 cc tube volume).

The comparison might not be appropriate since the brand new Cricket has not been settled and adjusted to her maximum potential.

Happy New Year!:D

Endo

Thanks Trygve.:wink:

Robert, if you analyze the slope of your first 10-shot vs. the last 5-10 shots before speed drop off, the first 10-shot consumed more airs (see green lines). Based on the rate of air consumption at high pressure range (~210-220 bars) in your gun, one can predict the pressure should be around 110 bars at the end of shot #60 (assuming the linear drop of pressure per shot). But this is not the case, your remaining pressure is about 130 bars. So, it appears that, in relative term, high pressure consumes more air (or low pressure consumes less air). In my case, 193 bar fill is associated with ~10 bars deviation. And in your case, 220 bar fill is associated with ~20 bars deviation. I think the best fill pressure is around 170 bars – in terms of air utilization and taking shot-count into the consideration. I think 190-200 bar filling is very reasonable. You don’t have to fill the gun so often and waste the air in the filling tube each time you fill. Just a thought.
Endo

In mid November, I experienced the speed of my gun dropped a lot and the speed could vary more than 20-40 fps between shots. I have no idea on what the cause of this sudden change. This gun has spit out at least 12K JSB Heavy pellets in past 11 months and should have settled by then. I did a thorough clean on the regulator, clean/lube the washers in the regulator and the chambers/valve/pin, make sure the tiny holes in the regulator and vent holes are patent and no obstructions, change all o-rings. Cleaned the barrel and set the regulator back to the stock position. This massive cleanup seems to fix the problem. The shot strings (~890 fps) showed a significant hump at the end of the string, meaning the regulator pressure is too strong or HST is too weak. To maintain at ~890 fps, I re-positioned the regulator by turning-in to 3 o’clock, adjusting HST to ~890 fps, and shot several consecutive strings from ~195 bars down to ~100 bars. The strings are very consistent. The difference in average speed between fills is within 3 fps. Here shows a typical one from 5 strings. The average speed of this string is 888.5 fps, SD = 2.4 fps with 10 fps extreme spread and average 2.3 fps variation between shots. There is still a very small increase in average speed about 2 fps right after 130 bars. 2 out of 5 strings didn’t show up this small hump. I got 70 “flat” shots from 193 to 104 bars. The air consumption is much improved from ~12-13 cc/ft-lb to 11.4-11.8 cc/ft-lb after this massive cleaning. It can be translated to gain 5-8 good shots in a fill to ~195 bars.

Ed has said that air consumption is much efficient from 200 to 100 bars than from 300 to 200 bars. Veerkracht/Robert is interested in this claim and wants to have some data to support it. Since I don’t have the guts to fill my gun to 300 bars (even above 200 bars) I did an analysis on the pressure curve of the shot string. I make a red-line on the pressure drop for the first 10 shots and it shows a clear difference in slope from the remaining actual “curve” (see first diagram above). This indicates that the pressure drop in first 10-shot is faster than the subsequent shots, especially toward the end of the string at lower pressure. This means the air is more efficiently used at lower pressures. This phenomenon is consistently seen in many strings I constructed earlier. The slope of pressure drop for the first 10-shot is different from that from the last 10-shot (see diagrams below with red lines). The regulator setting may also have some impacts on the air consumption under the same energy output (see last diagram below). They started out at the same pressure but ended differently. This suggests that the regulator and HST need to work together in unison to get the optimal air usage.

The changes in pressure drop are quite subtle (about 10 bars the most) at 100-200 bar range. I don’t know if the pressure would drop faster at the higher pressure range, e.g., 200-300 bars, but the string data suggest this possibility.

Endo