My HW98, 5 shots spot on then suddenly the next 5 drop about 4 mildots, then they come back up again. I change the breach seal still does the same. I thought it's probably the PTFE sleeve that I put in it, maybe its catching). I strip the rifle down only to find I hadn't put one in it. I look at the piston seal to seal its got a slightly rough patch on the edge but I have used worse. I check that the TbT guides are not over tight, they are fine. I re grease the rifle put it back together (thinking I should have changed the piston seal).
At the range the first 7 shots spot on, Yeeeeeah I thought then they dropped about 4 mildots again.
It goes through the chrony 11.75 ish for the next few shots then drops to 11.3 oh dear me I think to my self. I have changed the scope just to confirm it's not that. Have tried different pellets and it's just the same and cleaned the barrel. I tried tightening the axis bolt and now it's up and down like a whores drawers. I am perplexed I have a couple of things to try.
My thinking is now that leaves 2 things, the piston seal or the spring.
You may ask, did it do this before I put the TbT kit in, I can't be sure as I had only used it at 20 yards heard it boing and changed it quickly.
Over to you Guys for advice please, thanks in advance, Ade