Trusty computeer says this is fairly whimpy round and could only do 3731 fps with a 140 gr 6.5MM bullet for 5973 FPE. Min bbl length = 41 inches. Bbl life would be 100 to 200 rnds.

this feat is better duplicated with a 378 Weatherby stuffed with a 375/264 sabot matchning the expansion ration of the 7MM mag and needing only a 26 inch bbl. Barrel life would be the same as a 7MM mag as expansion ratios and pressure would be the same.

Recoil in the 378-S264 would be 41 FP in a 10 pond rifle...much better than the 80 FP from the 50BMG/264.

Problem is with modern powders and safe pressures, you won't push any particular bullet weight or diameter much past the 5000fps mark. In other words, even if you necked the 50bmg down to 17, you would be hard presses to get more than 5000fps.