Hi,
The rifle could be oversprung. If it's shooting too high, perhaps a weaker or cut down spring would reduce the recoil and drop the point of impact. It could also be the piston washer has perished and a replacement may make things smoother.
I find H&N FTT pellets work very well, as do flat heads such as Excites or Hobby but the latter are not suitable for bell target, so give the FTT a go.
Kind regards,
John
Currently looking for Baikal Makarov pistols with the following prefixes to the serial number: 98, T01, T09, T21, T22
Prefer boxed or cased but will consider loose examples too.