HST dial mod
Simple mod that attaches to the HST screw and allows you to dial in specific velocities to specific pellets or pellet weights. Can work for the Vulcan as well if you cut down an allen wrench to size.
You can use self-adhesive tape (I used shelf-liner) or print off some labels from your printer to make it neat. You can make the dial look much nicer. For now I just chicken-scribbled on it and marked 1,2,3,4 at 90 degrees apart, so each marking is a quarter turn. Can use it for any pellet, or mark the velocity for each pellet on a separate dial.
For example, with 18gr JSBs:
#1 = 800 fps
#2 = 840fps
#3 = 890fps
#4 = 920fps
For other pellet weights, change the tape with the markings or just make another dial for each pellet type.
I used a 15.8mm OD copper tube that I cut with a tubing cutter. Set two screws (better use rods like the factory HST adjuster) in epoxy inside the cut tube ring. Added rubber gasket coating on the threads so the dial will stay inside the HST screw openings.
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For me it depends on the gun/PCP and application ………..
I tuned both of my Crickets to max power with the heavies pellet that produce the most accuracy and FPE down range.
My Cricket 177 is tuned to send JSB 10.34g @ 920 fps which for my gun/barrel has the maximum FPE and is the most accurate there.
I tune it down the HST to what ever speed I need it to be for my application when pesting.
I found that if I tune down the FPE accuracy may suffer a bit but the shooting distance is closer when I do that so it’s more then accurate enough.
But my 22 std likes only one speed the best so I leave it alone.
On the other hand the Mutant …………… well what can I say …… … . it’s a Mutant ! 
~ Greg
Didn’t realize the HST was that repeatable. For Me it is set it and forget it because my guns ES goes up if the hammer spring is not set right. And I like it low
Cool …. very neat ….. I did a similar mod with two nylon pins I install/tapped into the factory HST pin holes.
But I marked only 2 locational speed setting that I use the most often for 18 and 16g.
I also used a large head hex in the affixing screw on the side so I don’t need a alien wrench tool to loose/tighten the HST in the field, just my fingers.
~ Greg
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Good idea GKU with the side screw. I will try that too.
Cricket and GKU, this is only the second time I took out my Mutant since I got it in a trade, and the first time where I messed with the HST adjustment. I had no issues dialing in the velocity back and forth, and I tried 4 different pellets between 14-18gr. The 14grs were close to 1,000fps with the same settings as with the 18grs set at 890fps. I was actually surprised at the shot count coming in at near 100 during both strings. I watched it fall off the reg at around 115-120bar starting from 250 bar and next time from 235bar. It was a nice steady slow drop from 890fps without any peaks, and I think I got about 6-8 shots off the reg to 850fps while using 18gr JSBs. My .22 Daystate Airwolf MVT (MCT with chrono) also starts losing its POI with 18gr pellets at around 110-115bar.
The reason I know the gun’s gauge is correct because I just bought a used JoeB Guppy that had an internal tank gauge that was off by 400psi compared to three other gauges (my large SCBA tank) that were part of the fill system and all three showed the same pressure. So when I filled the Mutant the gun gauge matched with my other gauges.