I have an airforce condor ss, and it absolutely LOVES the 27.5 & 28.5! There’s virtually no difference, accuracy wise, between the two out to 75 yds. (from my rifle). I have it tuned down to just over 5, still average over 900 fps! And they put a serious hurtin on critters! Have dropped grounders at 150 yds! The thing continues to amaze me. I’ve ran several different pellets through it, and by far, it shoots these the absolute best! Kudos NSA, extremely good pellets. Now, that being said, not all rifles are the same. My buddy has an older airforce talon, and it won’t shoot them, they get jammed up in the barrel, and air escapes backward. Maybe he needs a different diameter.