Air Venturi best slugs for avenger x 25

I know this is an older post -

I started running the JSB Exact King Heavy MK II pellets at 33.95 grains and clocking at 875 FPS. This was a tuning from the web - 175 bar and 5 turns and two nudges on the hammer spring - speed is +/- 3 FPS in eight shots and when I'm working right, the rifle does eight shots in a dime at 50 meters.

The H&N HP Slug Mk II in 34 grain shoots almost the same with the same tune - flys a little slower but groups well at 860 FPS

I have two running tunes - they come in at about 54 Ft lbs and 63 ft lbs -

I have tried 0.250 and 0.249 diameter slugs in several versions and weights - the HP Slug MK II there is almost no difference between the two diameters but in the H&N Heavy slug in 38 grain, the 0.249 flew 10 FPS slower and the 38 grain and seems a little too heavy for to get an optimal speed. the clock in at 795 and 785 FPS with a slightly lower ft lb impact

In theory, a slug should behave with the best BC somewhere around 925 FPS so I'm going to be trying 30, 32 and 33 grain slugs to see how they work with the two energy levels.

The 34 grain HP Slug MK II from H&N already does well so just looking for even better options and the 34 grain looks like it will do about 910 FPS and 63 Ft Lbs with a 210 bar tune
 
From my understanding, the Avenge X as not designed to shoot slugs. It shoots Pellets extremely well when you find the one the barrel likes. I guess, that beings it's your gun, you can shoot what you want, but slugs aren't your best option.
There seems to be a lot of debate about the idea lslug barrel and speed but the 25 cal Avenge-X actually does shoot slugs well - I don't have space to go any longer but at 120M, its still grouping well and the pellets struggle. At 50M it puts either one through the same hole 5 out of 8 shots.

This would seem to go against "conventional wisdom" about needing a faster twist and higher speeds (1000+ FPS) but they fly ok and are less impacted by the wind so it seems to be a viable option (after about 350 slugs so far)