I can see that one of the suggested .177 pellets for use in Bell target shooting (RWS Superdome) is only available in 4.50mm, so that save's the problems of testing and seeking advice on what "size" of pellet to use.

The bewildering choice of 4.48. 4.49. 4.50. 4.51 and 5.52 that we have for most of the flat nose match qaulity (semi-wadcuter) pellets makes life more difficult than it needs to be - in my opinion - with no clear cut reason for that amount of choice in the first place as the BBS thread on this subject suggests.

Another advantage to the Bell Target shooting - keep it nice and simple!