Edgun R3 .22: Shot String, Air Efficiency, & Trigger
This will be a long post, sorry about that. Ran into the dive shop to fill up the scuba tank yesterday. The shop owner put on a pressure gauge to show me how much the tank was filled, because I was “hinting” at him that I could only fill the gun to 180 bars (~2610 psi) last time with a full tank. The tank was indeed filled to the maximum pressure around 3100 psi in this new fill. Interestingly, again, I only could fill the gun up to ~180 bars based on the gun gauge; but the gauge in the fill adaptor showed 3050 psi (~210 bars). It seems that the pressure of my Edgun was somewhat under measured by 440 psi or 30 bars. 🙄
I tested a shot-string using Combro Chronograph, which is a very small and handy chronograph installed at the end of the muzzle area. The starting pressure was 180 bar (based on Edgun gauge) and JSB Heavy (18.1 grains) was used. The first shot was low in speed (878 ft/sec), but the subsequent 35 shots were consistent with average 916.5±4.5 ft/sec (minimum 910 ft/sec and maximum 926 ft/sec). The regulator came off around 130 bars (I think) because of a little rise in speed for several shots and then the speed dropped to around 840 ft/sec for about 13 shots in parallel with pressure drop. The POI (at 30 yards) started to drop slightly (~0.2”) at shot #37 (or the regulator was off at this point?) The POI didn’t further drop until pressure went below 105 bars. I got 35 good shots consuming ~800 psi (from 180 bar to 125 bar) from a 289-cc air tube with average 33.8 foot-pound muzzle energy, which is about 13.1 bar-cc/ft-lb efficiency of air usage. If using Zoco’s data – green-line shot string, 220 bar to 130 bar for 57 shots, ~32.5 fpe (http://talonairgun.com/forum/viewtopic.php?t=19488&postdays=0&postorder=asc&start=520), I got the number 14 bar-cc/ft-lb efficiency.
Based on the data from a shot-string of Royale 400 (without regulator; average 868 fps with 37 fps extreme spread) (http://www.network54.com/Forum/79537/thread/1318702313/FX+Royale+400+.22+-+90+shot+string+with+chart-target), which consumed 0.94 bar/shot (220 to 135 bars for 90 shots) with ~30.3 fpe from a 400-cc bottle, the air efficiency is 12.4 bar-cc/ft-lb. Using another shot-string (http://airgunadvice.net/viewtopic.php?t=12183), from 220 bars to 179 bars with 36 shots (average 954 fps with 28 fps spread) at ~36.6 fpe, I got the same number (12.4 bar-cc/ft-lb) for air efficiency. Using the data from the FX Royale 400 review video of Ted in Youtube, average 33.53 fpe and 20 fps extreme spread with high power, I got 11.1 bar-cc/ft-lb efficiency. If the medium power is used (884 fps with 31.4 fpe and 13 fps extreme spread), the efficiency will be higher at 9.6 bar-cc/ft-lb. It seems Royale is a little bit better than Matador R3 (standard length) in air efficiency without much sacrificing speed variation in the un-regulator gun.
I think Edgun can be optimized by adjusting the combination of regulator and power to reach max efficiency, but it will need a lot of trial. Or this is already at the optimal condition when Ed designed and set up the gun. What do you think?
p.s
I also installed a Harris bipod BRM-S model 6”-9” in late afternoon, and ran a few shots under high-gust wind (>20 miles/hr) before dark. It seems to improve the unstable sitting of the gun and increase the shooting accuracy. 😛 Will test more tomorrow if weather is good.
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Hey bud
I think you are on the right track. Just like OG said If you lower HST a little down to 900fps you will have about 50 regulated shots.
Here is my latest string from my R2 .22 Standard. JSB 18.1.
Its set at 910fps and get 45 full speed shots.
Tedd, thanks for the suggestions. As you said, I filled the gun slowly to avoid the increase in temperature during filling, the gun gauge does not register the pressure correctly. I will use the gauge in the adapter for pressure reference now. I will try to turn down the HST adjuster to reduce some speed to see if I can get more regulated shots. I ran out the air again, have to wait for next visit to the dive shop this weekend. 😥
Does your R3 .25 have better air efficiency than R3 .22?
Regards,
Endo
Endo, I have a Combro also and it is handy but, mine isn’t as accurate as my chrony.
Try turning the HST adjuster out and try a shot string starting at 890 fps. You should get at least 50 regulated shots at that speed.
I think that the Matadors gauge is there to give you an idea of the air pressure remaining. I use a good gauge in my fill assembly and go by it when filling. I also fill the gun slowly, It takes me a couple of min to go from 1700 to 3100. If you fill too fast, the air tube heats up and you lose pressure as it cools.
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F and D, that string looks very good! I found that my Matador, when set at 890, would give a couple more shots before it came off of the reg. I thought that I got 50 regulated shots but, this oldgoat doesn’t remember to well!
Endo, that is a good question. My 25 long version has a 388 ccm air tube, the 22 standard has a 289 ccm air tube. I get around 75 regulated shots on the 25 but, the air tube holds more air. When I get my R3 22 cal standard I hope to swap a 25 cal BSA barrel and my R3 25 cal breech onto it and see for myself.