It has been a while since I rechecked my Vulcan’s shooting characteristics. Mine is a 22 that I usually keep at 900 FPS. Its regulator was set to 135 bar using a regulator tester made by John Hagan.
I have been very happy with it, but it’s always fun to squeeze out a little more from our toys.
Here is shot string starting at 200 bar. I started at 200 just to reduced the amount of work. I normally fill to 250 bar and get about 25 shots before reaching 200.
Notice how it comes off regulation at about 135 bar. Also, the segment after regulation climbs. This is due to my hammer spring tension actually requesting a velocity below the max potential of the current regulator/air chamber/transfer port capability. If the regulator were set to match this velocity, around 125-130 bar, the regulated segment would be a bit longer and lack the rise.
I could have simply re-adjusted my regulator. That would have been the end of it. However, remember that the gun’s precision can also be affected by velocity. I also want precision in addition to consistent velocity.
To investigate velocity and precision, I shot groups at several velocities. I made certain the shots were all within my regulated pressure shot count. Because adjusting the hammer spring tension does not immediately take effect with the first shot, I followed the HST adjustments with a single shot to let the HST settle. The single shots were rather haphazardly aimed. Pay attention only to the 10 shot groups. The single shots do however serve as a scale against which to compare the groups.
I noticed that my usual setting, 900 FPS was actually grouping worse than velocities below and above 900 FPS. At max velocity 945 FPS, groups were widening again.
So, to get more precision, I could either decrease or increase my velocity. I wasn’t terribly interested in dropping down below 860 even though grouping was best just below 860.
Somewhere between 912 and 940 the grouping were pretty tight. I also knew from my shot curve, that going up in velocity would better match my current regulator setting.
I decided on 920 FPS to both flatten out my shot string velocity curve and better precision.
10 shot grouping at 920 FPS. Single shot to left. I can live with this.
I have been very happy with it, but it’s always fun to squeeze out a little more from our toys.
Here is shot string starting at 200 bar. I started at 200 just to reduced the amount of work. I normally fill to 250 bar and get about 25 shots before reaching 200.
Notice how it comes off regulation at about 135 bar. Also, the segment after regulation climbs. This is due to my hammer spring tension actually requesting a velocity below the max potential of the current regulator/air chamber/transfer port capability. If the regulator were set to match this velocity, around 125-130 bar, the regulated segment would be a bit longer and lack the rise.
I could have simply re-adjusted my regulator. That would have been the end of it. However, remember that the gun’s precision can also be affected by velocity. I also want precision in addition to consistent velocity.
To investigate velocity and precision, I shot groups at several velocities. I made certain the shots were all within my regulated pressure shot count. Because adjusting the hammer spring tension does not immediately take effect with the first shot, I followed the HST adjustments with a single shot to let the HST settle. The single shots were rather haphazardly aimed. Pay attention only to the 10 shot groups. The single shots do however serve as a scale against which to compare the groups.
I noticed that my usual setting, 900 FPS was actually grouping worse than velocities below and above 900 FPS. At max velocity 945 FPS, groups were widening again.
So, to get more precision, I could either decrease or increase my velocity. I wasn’t terribly interested in dropping down below 860 even though grouping was best just below 860.
Somewhere between 912 and 940 the grouping were pretty tight. I also knew from my shot curve, that going up in velocity would better match my current regulator setting.
I decided on 920 FPS to both flatten out my shot string velocity curve and better precision.
10 shot grouping at 920 FPS. Single shot to left. I can live with this.
