Air Arms Owners Club

Hello
Need to say before i start i know nothing of this guns history over the 2 weeks i have owned it, had plenty of AA guns before from 310’s to TDR’s and other US.
This one is a .177 S510 US, came with a god awful scope i am soon to be rid of but that’s not the cause of the issue. I am getting fliers, 2 or 3 in a mag.
Have cleaned the barrel thoroughly and checked the mod with a light for burrs from clipping and can see none, will shoot her tomorrow minus the mod to see if it makes a difference
My thought is a dirty slide and hammer causing low power shots hence the variation
Before i drill the AT is there any other suggestions ... if not a slide and hammer polish it will be

I have also tried the JSB Diablo and AA field in 4.52. Checking the forum on here my old US used to eat JSB Heavy in 4.51 so they were ordered this morning

First thing I would do, if you haven't previously had good groups with the gun, is test a range of pellets with a chrono for velocity and accuracy. My AA PCPs (incl. .177 US) are not particularly pellet fussy and will perform well with several AA/JSB die numbers in 4.51 and 4.52mm. But they still give poor results with some pellets - that includes some JSB die numbers for the same sizes.

An explanation of what you mean by "fliers" would be helpful: is this a few isolated major deviations from otherwise good groups; are they in similar/random directions; or is it a more general wide spread, vertical stringing, two or more distinct groups, etc.