Personally, I love to use heavier bbs than most people in all of my rifles and pistols. In my bolt action I use .4s, my m4 .28s, etc. My m4 actually shot around 380 fps, and I had some great success with the .28s. I would suggest you use at least .27s or heavier as this will really help with accuracy, and they are not as affected by the wind. Also, the heavier weight bbs can punch through small brush and stuff like that.
All in all, .27s or heavier. Mainly its what suits you best, so maybe try out a few bbs of each weight and see what you like best. For a starting point, go with .27s. Or if you are really hesitant on the heavier ones I guess .25s could work (but I dont recommend it).
All in all, .27s or heavier. Mainly its what suits you best, so maybe try out a few bbs of each weight and see what you like best. For a starting point, go with .27s. Or if you are really hesitant on the heavier ones I guess .25s could work (but I dont recommend it).