This is the reverse.
Proof got contracted to develop small bore stuff for the .mil sniper program because students were burning out .300 Norma Magnum barrels 1/2 way through sniper classes, and for the HICAR program.
They had previously done some development work on medium caliber auto cannon barrels.
Figuring out an exponential twist rate progression and rifling profile to deal with copper jacketed projectiles was a challenge according to the podcast. Medium caliber stuff and large caliber stuff uses driving bands, so projectile deformation isn’t as much of an issue.