Great read this thread, no one has mentioned 'smooth twist' so I will.
When I got my .177 fx bobcat mk2 new I ran h&n ftt through the it,it grouped brilliantly straight off I put a whole tin of these through with great results. Next I tried jsb express again a full tin with very good results indeed. Next jsb exact,again with the same results.
Ok the first half dozen of each type were not tight but they weren't bad either but tightened down very nicely.the thing is I've not cleaned the barrel at all? So far I've put around 2500 pellets through it 1500 of then being exacts as they suit my mtc ret the best.
yes they are all good quality pellets and no doubt it will spray others all over the shop but I honestly never cleaned the barrel between types with no problems. Smooth twist gets my vote for the most unfussy barrel I have ever shot 'I've shot plenty' will report when it goes off the boil.