When I tighten a Ruger into the stock, I start the front angled action screw first, and then turn it until just before it tightens.
I then insert the rear action screw and do the sme, leave it just loose.
The front action screw is then tightened about as tight as you can get it without straining with a normal size screwdriver. The nice thing about the Ruger action is that the front action screw pulls the action back and down against the recoil lug recess.
I then put pressure on the trigger guard to the rear and then tighten the rear screw down but not quite as tight as the front. The middle action screw is only tightened until it bottoms out and holds the trigger guard solidly. DO NOT TIGHTEN THIS SCREW.
Check to see that the floor plate freely opens and closes and you are done.
Allen Precision Shooting
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Be sure you listen to Fifty on the middle screw! This is the one that can really mess up your grouping. I use thread lock on this screw and just tighten until it bottoms out. If you tighten any further, you'll put strain on the action! The only purpose of this screw is to hold the magazine and trigger guard in place. The rear action screw actually does a great job of holding the trigger guard securely, while the front action screw does the same for the magazine. Use thread lock, pink nail polish, etc. on the center screw, and stop tightening when the screw touches the trigger guard. I've seen this before....
I had a Ruger 77VT in 22-250 that went to John Lewis at Carolina Precision for a full accurizing job and it really didn't make that much difference. Typical Ruger, four shots into a decent group but always one flier. Frankly, I've culled all of my Ruger centerfires from my safe. I know there are some really accurate Rugers out there, I just haven't been able to find one. When I get a gun like the one you describe, I move on...life's too short!
I once had an old ruger 77 in a 7 rem mag that had been bedded into a Brown Precision stock. It was a solid .5moa rifle. After one fouler it was good for an additional 12 shots, but at #13 it would shoot out of the group. I spent many hours experimenting with loads to get it to shoot that well. That said, I have to agree with rogerinneb. When I get one now that shoots like that it gets sold. Too many good shooting rifles around to waste a lot of time on a dog.
First thing I'd do is change scope check screws buy a box of factory ammo and see how that shoots. If it didn't group any better you have three choices send it back to the factory unaltered,sell it or send it off to a gunsmith. Bedding is a plus if wanting to keep the rifle and if it didn't shoot after doing that I'd just spent the money and have the rifle rebarreled since you are left hand and don't have alot of selections in rifles and found one that fits you pretty good. Well good luck