Another winter tinker that could be a long winded story but I’ll cut to the chase. It concerns my FX Wildcat, which has served duty in many configurations from 177 to 30 in compact (500mm) and sniper (700mm) form. It started out as a Mk3 tubed version and was converted to a BT through the addition of a plenum tube and bottle adapter. Its most recent config was in 500mm 30 cal but it was made redundant by the arrival of a Sidewinder mini in .30. I decided to turn it into a dedicated little 22 slugger with a heavy 1:16 liner. Nothing new there - Ted Bier and others have posted numerous videos singing the praises of the WC BT compact 22 slugger. The twist here is that I wanted to get it shooting the high BC Altaros 32.3 grain slugs at their favored speed of 880-900fps. I thought that might be a tall order at 56+ FPE, requiring some modification of the valve or deletion of the second reg. However, the little powerhouse came through without having to exceed 150bar. I was also able to keep the stock pellet probe, which keys into the tail of the Altaros slugs ensuring perfect axial loading and smooth magazine operation. YMMV, but pin probes have never done me any favors.
Here’s the config details:
1:16 500mm heavy liner, cleaned and installed into the TP and jam nut with a tight fitting Teflon tape wrap and only one 8x1 oring at the top of the jam nut. Another personal preference over the seemingly wobbly stock 3X oring setup.
CF liner sleeve bonded to the liner with silicone sealant.
Stock pellet probe with port opened up to match the TP without removing any of the circular face that contacts the slug.
Huma slug transfer port.
Heavier brass hammer weight from the Huma WC/Maverick tuning kit with stock spring.
180/150bar Reg1 and 2 and HST set 2 turns out before coil binding prevents cocking.
Regarding the tune, a 150bar plateau speed of 895fps was hit at around 1 turn out from binding on the HST. The shots were loud and clearly wasting air. The surprise was that, even with the excessive air, the slugs seemed to be hitting the same spot. In any case, I dropped the speed until the shot cycle settled. The resulting speed was 880fps and the ES was 4. I’ve read so many times that excess air will destabilize slugs so I wasn’t very optimistic about settling so high on the curve (98.6%) but from what I could see, the slugs were stacking
and the sound was snappy. Perhaps the heavier slugs are not so easily upset? Perhaps it’s an old wives tale born from expectation rather than empirical testing. IDK.
So, here we are with a WC compact 22 shooting 0.18BC slugs at 880fps for 56fpe! For context, that high BC means that the slugs are delivering 47fpe at 100 yards. That’s a pretty useful compact rig. I’ve run it before with a standard liner and light slugs and it was pretty good. But this is (so far and fingers crossed), way better. Here’s a group of 8 at 50 yards with the spent stack of slugs plucked from the duct seal under the target shown at the top. These included the first shot of the day…
I’ll be taking it out further in the next few days.
Here’s a pic showing the guts after diy conversion from tube to BT. From L to R, BT plenum, original reg section (which I think gives it a slightly larger plenum), another small plenum and then the bottle adapter.
Finally, a pic of the pellet probe keyed into the base of an Altaros slug. I suspect this plays a role in the exceptional accuracy of these slugs.
We have NSA blazing the projectile trail with lowering the price of the formerly very expensive slugs. 
However, I am convinced that a good many of us would have use for a hollow point projectile that: 
does not leak whatsoever and I have a complete bro cock seal kit in case there ever is a leak check out the reviews on this gun. They are excellent.
