Shooter (starring mark wahlberg) question

[Nyles]

In the (superior, but also set in the early 90s) book, Swagger uses a Remington 700 .308 and the assassin used a Model 70 Bull Gun that's been rebarelled to .318 with a .10" paper patch. It makes alot more sense in that context. Incidentally in the book it's also heavily implied the same assassin used the same method to shoot Kennedy with .268 Carcano bullets patched to (I think) a .280 bore)

I supposed for the sake of argument in the movie they could have used a high pressure plastic sabot like a Savage 10ML muzzle loader (.452 pistol bullet in a .50 barrel propelled by smokeless shotgun powder) and had it make more sense, plus use some 2010s technology.