Rifle specs / mods:
.22 700mm
Superior heavy liner with carbon fiber sleeve
Ernest Rowe dual high flow transfer port
Huma high flow pellet probe
2x hammer spring spacers from FX slug power kit
Details for 27.5gr .218 dia Nielsen slug tune:
165 bar 1st reg
135 bar 2nd reg
valve 1.5 turns open past 4th line on 4 line valve housing (full open)
16 macro
2.75 micro
955 fps
Since this rifle is going to be used for ground squirrel blasting 90% of the time, I tested the 24.8, 27.5, and 28.5gr slugs, any of which provide ample muzzle energy for squirrels at longer range while still being decent on air use to give a higher shot count per fill than the heavier 31.2gr slugs. The 27.5s have a good BC for their weight (0.090BC) and luckily my barrel liked the 27.5s best. For info, max velocity plateau for this setup with the 27.5gr slugs is 990fps. I set the macro to 16, started the micro at 1.25, and worked up using the micro only to find the velocity peak and then backed off the micro from the peak down to 980fps and shot groups dialing the micro down little by little looking for best accuracy which ended up being 955fps.
Adjusting this way having the macro at 16 for the slug tune makes it easy to remember that 16 is the default slug adjustment. I get about 72-75 shots per fill with this setup.
Details for 18.1 gr JSB pellet tune:
Everything the same as the slug tune, except adjust macro to 4. This result in 925fps. Accuracy is quite good but could be better. Tried shooting groups from 825-950fps and 925fps were the best. My hunch is the twist rate of the superior heavy liner might be too fast for the lighter 18.1gr pellets. Still, it's a good combo for smaller backyard or closer range pesting at 34 ft-lb when the slugs might be overkill. Also good for closer range target practice in the backyard since it's much easier on air use than the slug tune. Zero changes up 0.3 mils and left 0.7 mils from the slug zero.
Details for 25.4 gr JSB pellet tune:
Everything the same as the slug tune, except adjust macro to 12. This results in 935fps and absolutely fantastic accuracy with the 25.4's, they seem to get along very well with the superior heavy liner. 49 ft-lb, good for larger critters or longer ranges in places where the slugs might be overkill. Zero changes up 0.2 mils and left 0.2 mils from the slug zero.
