Hi! Dave, I have a 300S universal that seems to like the JSB 7.87 grain pellets best. I don't shoot it much anymore but it is definitely the finest shooting springer that I have ever shot by far and Ive shot most of them!! If they had a bit more power you would see a lot of them still in use for field target (spring gun class) as they are almost indestructible and don't seem to have the inconsistency of other springers. People have tried to up the power of them but sooner or later end up breaking something as they were meant for ten meters and that's were they shine! Although in no wind conditions they can shoot VERY well at longer ranges. The are also very popular with guys that shoot twenty five yard USARB bench rest indoors and I believe the 300 holds the record for the spring gun class. Good luck and have fun!! J.L.