t got one on order. Would 300 grain lead bullets for reloading a 45-70 mess up the bore. They also have a copper plate at the base of the bullet to prevent powder from a regular bullet melting the lead.
I would say as long as the copper plate is smaller diameter than barrel it should not affect anything. If it is touching the lands of the barrel it will wear them down over time. From what I understand or have ever read the airgun barrels are not designed to use copper bullets only lead.