Quote Originally Posted by clipper View Post
If it is a TL (he of FB fame) 22mm skirtless piston I have the same in my full length TX .177, and have found QYS to be the best

I tried all the different headsizes of JSB Exact, AA Diabolo, FTT, RWS, in the rifle as standard, when it had a TbT short stroke kit, and in its current state, and nothing even came close to the consistent FPS, grouping, and accuracy of the QYS Streamlined 8.48gr 4.50mm head

Mine is running around 10.5ft/lb, standard AA spring, no preload washers.... it did take three strip and rebuilds to get the stroke length correct but it is now almost recoilless, completely impervious to hold (although I still wouldn't clamp it in a rest like a PCP!), and single figure FPS variance

Give TL a call when you have enough time to absorb everything he will tell you.. the man likes to talk! My best guess with inconsistency like you describe would be breach seals, excessive amounts of grease/lube or a spring that it is out of shape, poorly dressed, or has been heated and squashed
Thanks clipper, I'm hopeful the breech seals will sort it. Yours sounds awesome & I'd be happy with 10.5 in this rifle, I might give some QYS a try too.