Final update for the .22 AGT80
Finally settled the .22 down, here is how the rifle ended up.
Refitted 16inch HW90 barrel (same as 16inch HW80 barrel although the bare 90 barrel is slightly lighter weight)
Added 280Gram barrel shroud (finishes flush with the end of the barrel) its just to add weight
Originally the short stroke using the LGV piston seal was 11mm, I have now swapped the LGV seal out for a 25mm Vortek seal which added just over 2mm stroke..so rounding down I have increased stroke by 2mm so now only -9mm overall.
Changed the spring for new unit with 3.25mm wire, 20.5mm OD, approx 240mm free length (I will count coils and update) This spring has fewer coils per inch so is stiffer, its also slightly longer than the spring I was using originally and needed no extra preload. Power remained the same with RWS Superdomes however power increased with AA fields by 0.2fpe.
End result is a slightly faster firing cycle, hold sensitivity has massively reduced although the .177 is almost not hold sensitive at all…the .22 is now MUCH easier to shoot. I will swap the straight setback trigger bade for an extra set back unit from Rowan Engineering which I feel will help a great deal also.
For now its sat back in an OEM stock, I find it easier to shoot in this stock over the CS800 it usually sits in, if this proves still the same the CS800 will be up for sale. If the rifle does stay in an OEM beech stock I will modify it somewhat like I have with the 0.177 in the mk1 stock…or i will look our for a mk1 HW80 stock and modify this.
Final thoughts on tuning the HW80, the 305mm Carbine barrel thats popular now is to short, I tried 2 on this .22 with one being fully shrouded, while good barrels they just did not help balance the rifle well and are not as efficient as a 16inch barrel. I could tell right away with the 16inch barrel reinstalled the gun had settled down considerably.
The .22 HW80 LGV piston conversion needs more work that the .177 for UK sub 12fpe use, for my USA readers or those with FAC you could leave the stroke at 79mm for the .22 but run the rifle up around 16 to 18FPE (It will do this power ) I would imagine the rifle would not feel any different to the firing cycle i have with the .177…seriously smooth to shoot. For UK use the .22 looks to need 70 to 71mm stroke (approx 34.5CC of air)
The single thing I may try is converting the piston to an O ring seal, this will quicken the shot cycle even more and may dial out what hold sensitivity there still is…its slight though so may not be worth the effort….its under debate