Been shooting the M77 Mark II in .300WM for a few years now with satisfactory results. But last season into this year my groups have become more and more erratic. By this I mean one hole will be touching the 10 ring, the next might be in the 7, and third could be wherever. They sort of wander. I haven't changed my shootong style at all. I zero at 200. I haven't changed ammo. I'm not sure what's happening but the gun has become "unpredictable". It's within' close for some guys, but I like the 10 ring at 200 and haven't been getting it at the range. So it's no longer trustworthy.

What could have happened?
I hear and read stories about how Rugers are not the gun they used to be since the son took over and the quality has gone down. I've had this rifle for several years and the accuracy I could once depend on seems to have wandered off.

Any ideas?
New barrel?
Scrap it for a new gun?

I had two Ruger M77 with the tange safety that the stock swelled on them. When that happened I was shooting all over the place. Firts on was a 338win mag. Had it glass bedded and problem was solved. The other one a 7mm mag. I traded for a Remington model 700BDL.

I'll bet the gun is ok, I have a tang Ruger and my brother does as well, nothing wrong with a Ruger...

The nice thing about Rugers is that you can get to each scope mounting screw to check it...That's the easiest thing to eliminate...As mentioned, remove the bolt and clean the barrel, I would also check the screws that hold the barrel to the stock, the front screw should be tightened first and the tighest, the rear screw should just be snug...

I have also seen rifles that quit grouping their "favorite" ammo, I'd try a few more brands...

Finally, check the scope, either replace with another that you know works or try shootinng a square to see if your scope is holding zero.

If all this checks out, let someone else try shooting it.

Agreed. I would clean itthoroughly with mynormal solvent of choice then hit it with a dedicated copper removing solvent like: sweets 7.62, Barnes CR10, etc.

I would follow the process shown above as well. This was happening to my Dad's 300Wby, which ultimately required a new barrel. He was never good at keeping his guns clean...

Butch's bore shine. Clean several times. Make sure you get the chamber/throat. Try again, and you might try different ammo. The barrel might've broken in and doesn't like the old ammo. If things don't improve, things will start to get interesting You might glass bed, recrown, or rebarrel.

years back when i wanted a 300 win mag one of the things i saw in a review is that the barrels can get burned out after something likem1000 rounds. dont know if its true.i would check the bedding-scope - and mounts. use copper cleaner and a good bore light. after that get a gunsmiths opinion.

Don't be afraid to havea 'smith at least LOOK at it. I had a similar problem with my 7 mag a year ago. I mean, it was shooting EVERYWHERE but where I aimed. I would be fortunate to keep 3 shots on a sheet of notebook paper at 100 yards. Went through a bunch of of the 'usual suspects' as far as trying to figure out the problem. Finally took it to a gunsmith who figured out there was a tiny 'bulge' near the end of the barrel. Must have had a bit of dirt/ice/snow/whatever in it at some point when it was fired, which created the bulge. The 'smith cut off the last 1.5" or so of the barrel, recrowned it, and $55 later I was back to shooting MOA with factory ammo.

Good stuff everyone. Thanks. I am religious about cleaning guns after shooting, or even taking them for long walks. It has a synthetic stock (all weather model) and piller bedding (on any Ruger) looks like it would be a nightmare! The scope gets checked regularly. And it's a Nikon Monarch, good quality.

I just noticed that I can not slide a dollar bill between the barrel and forend of the stock! A neighbor suggested it. Could that cause irradic shot placement?

If you have uneven pressure from the stock on the barrel, the gun tends to shoot erratic, and the more you shoot it the barrel warms up and creates even more pressure on the stock. It will continue to shoot worse the warmer it gets, usually. Free-floating may cure it. I generally like about 1 1/2 to 2" of the barrel solid bedded, and the rest free-floated.
Another thing that comes to mind is the question of do you know if the lot numbers of your factory ammo have changed from when it used to shoot OK? If you have an old box from the "good" ammo around maybe holding empties, you may want to check the lot nos. with the new stuff that is giving you trouble. I've had guns turn from great shooters to barely adequate just with lot no. changes. Not terribly erratic, just not what it used to be. Handloading usually remidies this when the right combo is found for the gun.
You say you clean your guns faithfully, but unless you are using a good copper solvent like Sweet's regularly, you could have a copper build-up problem that will definitely affect accuracy.
As was mentioned before, keep your guard screws tight also.
Just a few things to think about...............