Safe on which end?
H&R will tell you that levergun loads are safe, but the SB2 frame of the BC is the same as that of the Handi which is factory available in .500S&W with a SAAMI MAP of well over 50kpsi, which is in Ruger level pressures of the .45-70. But most likely, your friend will not want to shoot those loads unless some recoil reduction measures are taken.
The 45Colt BC has been discussed at length, there are several threads on it, but it won't be available for at least another month or 2. It can be seen at H&R's web site for those that haven't.
Tim
http://hr1871.com/