pellet weight

I was thinking of making a pellet mold for a .25 cal airgun. What would be the max weight that you could shoot out of pellet rifle without damage to any internal parts. I know when you add more weight the more pressure your gun is going to have to deal with. Is there a rule of weight vs power to safely find out the max the pellet can weigh? Any info on this I would sure help me out. Thanks again.
Richard
 
You can shoot what ever your gun has the power to shoot out of it. I would use a weight that can go at least 800 fps in a slug or 900 fps in a diabolo. You can gauge it by how fast you shoot heavy pellets. If you can shoot JSB heavies well then a slug in that range would be a good choice. If your gun can not shoot that heavy of a pellet I would not waste your time with a slug.