Only two of my guns like JSBs best, my P35-25 and my 25 caliber Avenger. The P35 likes the heavies and the Avenger the Kings (actually the FX 25.4s shoot at least as well). So I do not shoot a lot of JSB pellets. I've weighed a bunch of 25 caliber trying to figure out why my cast pellets do not shoot well in my guns. I found higher variability than in my cast but guns that like them still like them. I've checked head size in 177 and 22 and they were as consistent as the H&Ns I shoot in those guns.
My main reason for posting is to reinforce Scott's input. Domed pellets work great for hunting. "Hunting" pellets are fine if that is what your gun prefers but if the domed shoot as well, I would use them (and I do). If pellets expand their penetration is dramatically reduced. That can be OK if you have plenty but is not OK if you don't have plenty. From my way of thinking a 177 pretty much never has an abundance of penetration. I calculated the percentage of area destroyed by a 177 pellet with zero expansion for a squirrel and then related it to the much bigger cross section of a deer. I think you need a 0.75 inch hole in the deer to destroy an equivalent percentage. To me that means a .177 hole is enough. That is also my experience. I have used my one 177 less than my multiple 22 and 25s but the 12 tree squirrels I've taken with it have died quickly except for one shot I badly misplaced. That squirrel died close to where it fell but we could not find it. I think it crawled up under a bush. My dog found the degraded body a day or two later. An expanding projectile would not have helped, it probably would have made it worse by reducing the penetration depth.
To me hunting pellets were invented by somebody wanting to sell more pellets. They just are not necessary or even always helpful. If you already have domed pellets your gun likes at least as well, my strong recommendation is to use them.
