I shoot the Buffalo Bore 300's through my 25-13 as a large critter defense load. It's a thumper (bites on both ends), and I don't shoot many, but they haven't loosened the gun up. I have talked with the BB guys and they say they are "safe" to shoot in the gun, meaning it won't blow up, but they may loosen the weapon faster than standard loads. I did a bunch of research, and it seems as long as you stay below 25,000 cup or so you won't have a problem. Some recommend a 32,000 cup limit. My hand hurts enough with the BB load, so i don't plan on going any hotter. Like I said, not pleasant to shoot but less pleasant for any critter I'm facing.