Seconding the opinion above - No! The ,257 Ackley Improved was probably that most era-popular chambering and a pretty decent custom chambering yet today. Of course now eclipsed by the plethora of other "factory" rounds. You might well at least be able to find one of those newer chamberings of same bore diameter, only a reamer away from some contemporary rounds. 'If', a longer cartridge, needing to modify or pick up a magazine box & perhaps spring & follower appropriate. Such available 'at a price'!
What you don't have is a collector 'pre M 70. What you likely do have is yet potentially a darn good gun, all else equal!
Good luck!
Best!
John
