Clearly your bullet is not going to sleep…
100 is where you start dialing in your load. Not where it ends. Start looking at charge weight. Then twist vs. bullet.
Also, what is your group looking like? Stringing left? Right? Vertical? Flyers? Called flyers? Wind.
This is nothing new in handloading. It’s part of the fun.
Last, A good precision rifle should be well… well under 1moa at 100 anyway. So if you are getting 1” groups at 100, not 1/2” or 1/3” with handloads…. Look at rifle? Scope? Ssetting parallax right? (A big thing folks don’t understand). But clearly you do! Because you shoot modern guns and calibers and have handloading dialed in.
But that is not the issue here… it is a 1950’s savage! It’s not going to print much bigger than minute of deer at 300… also, possibly too light a bullet. Back then 180 grain was sort of “the hunting” round in .30. Probably twist rate was optimized for it. Try slowing it down and using a 180.
Loading for old guns (and expectations) from wood stocks, pencil hunting barrels and even old scopes is far different from modern stuff.
It will dial in better. Maybe. But remember, at 300 yards that rifle would have brought home a deer every time with a 8” group! Minute of pie plate. One holers at 300 came 40 years later!
Post some pix… and stop by vintage. We appreciate that stuff over there!!!
Sirhr