My first inline was the Magbolt .50. I've taken quite a few deer with the Platinum Powerbelts. Open Breech and not a true bolt action. I tried the breech plug mod and a home spun bolt head to shoot Blackhorn 209 but still had misfires. May try again someday but redirected to a TC Impact .50 for using Blackhorn and the CVA Accura .45 1-22 twist to try a 45 cal. Spent some $ but maybe safer and cheated the Doctors.
Looked on Armslist for the CVA 45 Magbolt, Hunterbolt, Firebolt, Elkhorn but they got pricey and decided retail was a better choice. The Elkhorn is top of the line in that series, not sure if came in a .45. The firebolt in .45 would be nice for a 777 rifle.
The .45 is a 1-28 Twist.