m77 accuracy

jjohnwm

jjohnwm

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I've got an accuracy problem...not sure if this is the right forum?

Anyhow, I have a Ruger m77 MKII in .300 Win, one of the very early MKII's when they were still push-feed. In its original stock, the ugly semi-skeletonized black synthetic job, it was MOA with a number of loads, and near-MOA with almost anything. It was and is stone-axe reliable, one of my go-to rifles. A year or so ago I put it into a Hogue overmolded stock, the one with the aluminum bedding block. I expected great things, but to my dismay accuracy deteriorated to a best group of around 2 inches. I fiddled and diddled and finally began to wonder if the full-length bedding of the original stock was preferable to the full-floated treatment in the case of this gun. I inserted a small rubber washer, maybe 1/16" thick, into the barrel channel at the very tip of the stock and snugged up the bolts. Instant improvement, sub-MOA out to 300 yards, but it seems to need a warm barrel to do it. With a cold but not-cleaned (i.e. several shots fired, but allowed to completely cool between groups) barrel, accuracy is still around 2 MOA. What the...?

Am I on the right track here? I've only shot groups with it on two occasions since this most recent surgery, so I'm not really sure of anything yet. I realize that for hunting purposes it's fine as is, but still, I find it tough to accept a loss in accuracy. I know the gun can do, and has done, better. I don't even want to increase accuracy, I'd be happy to just get back what I used to have. I generally clean my barrel after each shooting session, and rarely shoot more than 2 boxes at a sitting. I shoot mostly on my own property, so I have the luxury of allowing the barrel to completely cool between groups, i.e. usually 20 or 30 minutes of cooling.

Also, can this rubber-washer tweak be considered a permanent fix, or will the washer compress over time and change upward pressure on the barrel? After the washer was installed, groups were moved upward about ten inches.

This gun is going with me to Quebec this September, so any help would be greatly appreciated.

John
 
The washer will deteriorate eventually, but it will take a while. An epoxy/bedding compound patch at the end of the fore end will likely be more permenant. You obviously changed the way the barrel and receiver vibrate when fired by changing the stock, so either tune the load/gun to the new stock or go back to the old stock. Also, just because a rifle stock has an aluminum bedding block doesn't mean it doesn't need actual bedding, it can go either way, usually however, it will require bedding to be at it's best. FWIW - dan
 
The rubber washer may not be enough pressure on the barrel. When the barrel heats up it may apply more pressure on the washer, giving you better accuracy. I'd try the bedding patch, it may work better then the washer.
 
I'd take small piece of card stock (cereal box works), around 1" x 1/4" and fold it in half length wise and epoxy that about 2" back from the tip into the barrel channel. Just use plain old hardware store epoxy, it is easier to remove if there is an issue and is more than strong enough for this application. Make sure the cardboard is covered in epoxy so the cardboard cannot be effected by moisture.
 
I have a M77 in 7mmRM that does the same thing, but I have noticed a trend, the first shot from a cold barrel is dead on, as this is where I have it sighted for hunting. The next shot is high and to the right about 2", and the third is to the right and a little high. Clockwise pattern as the barrel warms up.

I am thinking of restocking and rebedding it some day.
 
M77

I have an M77 In 220 swift, and literally shoot thumb tacks with it at 100 ($.25 a piece), anyways it has a Douglas barrell and is sitting clear of the stock, you can run a $20 bill up the full lengh of the barrell as far as the reciever and not touch, the only time the P.O. I moves is if I shoot fast enough to get it too hot to touch. I'd suggest trying to put your old stock back on and test the accuracy again. I had the same issues with a 8mm Mauser that used to shoot fantastic untill I bought a better stock, laff.

M.
 
Thanks for the insight, guys. Blargon, I think you hit it closest. The idea of the barrel heating and thus increasing the pressure on it seemed easy to check, so I removed the barreled action from the stock and inserted a second washer on top of the first. The POI immediately shot upward another 8 inches or so, but the groups tightened up very consistently. I definitely will replace the washers with a more permanent bedding-compound pressure pad, but I may leave it as is until after my hunt. It's back to about .8 inches from a cold barrel, and I don't want to mess it up this close to the trip.

Thanks again, everyone.

John
 
I found my Ruger much more cold-hot consistant if the barrel is floated.
If I was in your place I'd be more inclined to look for a bedding problem in the action & leave the barrel free.
But each & every rifle is different your results may vary :p
 
You might even consider drilling and tapping two holes in your forestock and epoxying two threaded inserts in place (helicoils). Then screw in a couple of set screwsto apply pressure to the underside of the bbl at slight angles as well as just upward pressure.
Many companies use forearm pressure to stabilise vibration harmonics, it's a cheap and quite reliable method that works well, until something changes. The changes can be caused by warpage if wood stocked, or heat if plastic stocked, or by changes in torque to the front and rear action screws when reassembleing after cleaning etc.
The two adjustable forend screws can save a lot of time and effort as well as being very easily tuned with load changes. bearhunter
 
Bearhunter, that's an interesting idea. Sounds like it would function sort of like the BOSS system, without looking butt-ugly. I would assume that instead of using inserts that I could just drill and tap the aluminum bedding block and use set screws?

John
 
If it were mine, I would have the action glassbedded and float the barrel and then go from there.

I would not be bedding the forend until the action was properly bedded or I think it will never shoot consistent.

Bedding is required to get the best out of any "drop in" stock IMO.
 
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