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Velocity Adjustment to .22 Marauder


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#1 Air Rifle Hunter

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Posted 30 September 2011 - 11:47 AM

Well, I ordered some 18.1 JSB Diabolo Exact Jumbo Heavy Pellets and I'm now using them in my .22 Marauder for hunting. I wanted to see if I could get a little more velocity than the current 840 FPS average that I was getting with only adjusting my Velocity Metering Screw Counter Clockwise to up the velocity (currently it had already been turned 1/4 turn CCW). So I took the stock of and took the set screw out. I then went about turning the Velocity Metering Screw another 1/2 turn Counter Clockwise (for a total of 3/4 turn CCW from factory settings) and put the set screw back in and the stock back on. Next I pulled out the Chrony and set up a target. The following are the readings for a 30 shot string starting with an approximately 3000 PSI fill.Starting Fill Pressure = 2950 to 3000PSI (plus or minus)Shot__FPS_____Shot__FPS_____Shot__FPS1 = 821.9_____11 = 855.5_____21 = 873.22 = 827.6_____12 = 857.1_____22 = 877.23 = 831.0_____13 = 864.3_____23 = 873.64 = 839.1_____14 = 862.9_____24 = 872.25 = 843.7_____15 = 865.6_____25 = 869.46 = 844.6_____16 = 869.4_____26 = 870.77 = 836.7_____17 = 869.1_____27 = 869.48 = 847.5_____18 = 869.4_____28 = 863.49 = 853.4_____19 = 874.2_____29 = 863.010 = 856.2____20 = 874.3_____30 = 857.1Ending Fill Pressure = 2100 PSI +/-Low = 821.9, High = 877.2, 30 Shot Average = 858.4, Extreme Spread = 55.39 & Standard Deviation = 15.42. I think next time I shoot it, I'm only going to fill to around 2850PSI or 2900 so that it starts shooting at around 840FPS +/- and builds up to around 870+ FPS and then tapers back down to around 840 FPS +/-. I like that I didn't have to change any of the other settings (Hammer or Stroke) to get the velocity more where I want it while using my air supply fairly well (not being an air hog). I also like that it hit around 860 and above and stayed there for around 20 shots before looking like it was starting to drop off a little more quickly. At 865 FPS and above with the JSB 18.1's I get 30 FPE or better at the muzzle and I like those numbers because it means more energy transfered to my target. Accuracy it still spot on too! Now I've just got to wait a couple of weeks until I have time to get out and hunt again to test the effectiveness of the adjustment. :)

#2 Brant

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Posted 30 September 2011 - 12:10 PM

My Marauder .25 does best with a 2500-2600 fill down to 1500. Your sweet spot looks similar the way it is tuned.

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#3 CBR400RR

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Posted 05 October 2011 - 05:18 PM

I have mine shooting around 897-900fps

.177 Custom 1377c, .177 TX200 MKIII, .177 FWB 300su .177 R.A.W. TM1000, .22 M-Rod tuned, .22 AA S410 - SL XTRA FAC, .22 Theoben Rapid MKII AZ tuned, .25 Daystate Air Ranger tuned, .25 HM1000x, FX Boss .30


#4 Air Rifle Hunter

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Posted 05 October 2011 - 06:20 PM

With what pellet? Did you ever happen to find what your settings were?

#5 CBR400RR

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Posted 05 October 2011 - 06:37 PM

JSB 18.1 and I can't remember, sorry.

.177 Custom 1377c, .177 TX200 MKIII, .177 FWB 300su .177 R.A.W. TM1000, .22 M-Rod tuned, .22 AA S410 - SL XTRA FAC, .22 Theoben Rapid MKII AZ tuned, .25 Daystate Air Ranger tuned, .25 HM1000x, FX Boss .30





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