I have a Ruger M77 Mark II in .300 Win Mag. JUST .300Win Mag, no RUM or Short Mag, no newfangled nonsense. Anyway, EVERY time I pull the trigger the barrel vibrates so bad it made the factory stock sing like an anvil. With the new Hogue's Overmolded stock it is now SILENT but still vibrates badly. I now know why it was in and out of the pawnshop. I suspected some such. The barrel is very slim, I think would be fine for a 30-06. I really don't care as I am going to have it re-barreled with a fatter tube this year, action job, etc. But what in the WORLD is causing this?
Will probably drive it up to Douglas Barrels and get a Match tube put on, have it squared and trued, lapped if it needs it. As a Certified Hillbilly I won't be needing to shoot further than 1000 yards, so the old WinMag is all I need for it's Purpose. It'll be tough to find enough open ground for a 1000-yard shot, hereabouts. Any ideas/suggestions would be appreciated. Criticisms merely ignored or chuckled at. Thanks much,
KY Jim

Add a pressure point to the end of the forend. You can loosen the guard screws and place some folded up paper under the barrel at the end of the stock and then tighten the guard screws to see if that works before doing something more permanent.

If that does the trick you can use modeling clay to make a little dam in the barrel channel and then place Acraglas near the end of the barrel channel. Then install the barreled action in loosely. Hold the gun un a gun vice upside down and hang a gallon milk jug of water from the end of the barrel and then tighten the action screws. This should yield around 8 pounds of upward pressure to the barrel.

KY Jim, how does the rifle perform otherwise? You're not in the Jelly business are you?

Seems to shoot well enough, haven't had time /money to really Work It Out, waste of time due to planned changes. Nope, no Jelly, LOL. I'm Jim, who lives in Kentucky, therefore KY Jim.

Ky; All barrels vibrate to some degree, the thinner the barrel the greater the vibration & vice versa. I believe it's actually a circular vibration imparted by the spin of the departing bullet. As long as the barrels settles into it's original position before the next shot you will no doubt have an accurate rifle. That is why many rifles have a free floating barrel so that no touching of the stock prohibits this return to position (a very basic explanation). FWIW --- John303.