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M-77 accuracy tip

This is a discussion on M-77 accuracy tip within the Ruger Bolt Action forums, part of the Rifle & Shotgun Forum category; I am a new member to the forum and have this tip that I learned many years ago on accuracy issues with M-77's. I did ...


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Old December 2nd, 2013, 04:08 PM   #1
 
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M-77 accuracy tip

I am a new member to the forum and have this tip that I learned many years ago on accuracy issues with M-77's. I did not invent it, but rather read it in some magazine article on Ruger M-77's back then. I first used it on a 1987 M-77 with tang safety and recently used it on a new Hawkeye, both 308's. It involves pressure on the steel magazine box that is squeezed between the action and the floorplate and trigger guard. I have found that best accuracy from my rifles has been when the steel magazine box is a little loose, such that you can move it back and forth and up and down just a little when everything is tightened down. If you cannot get a little movement in it, then the action is tightened down against the magazine box and pressing on the tab on the rear of the floorplate hinge and the front of the trigger guard, rather than on the stock or the bedding in the stock. This causes wildly variable groups.

This can be checked for effect on your rifle by assembling it without the magazine box, tightening it down and shooting the rifle one round at a time placed in the chamber by hand. If groups improve, then the lack of magazine box free-play may be an issue.

The remedy is either glass bedding to a thickness that raises the action a little and gives a little free play to the magazine box, or using a dremel tool to grind a little off the front and back ends on the bottom side of the magazine box. I have tried both and had great results. Improvement can be as much as reducing 2-3 inch groups (3 shot 100 yd) down to 1/2 to 1 inch groups. This has not caused any feeding issues, probably because the magazine follower spring pushes the rounds and magazine box upward towards the action and it is then in the correct position for good feeding.

On the Haweye, which shot 2-3 inch groups with most all ammo (some were worse), I tried a Hogue overmolded stock with full length aluminum bedding block. When all tightened down, the magazine box was quite loose, and the rifle shot great (3/8" 3 shots at 100 yd with my pet accuracy reload). I didn't like the Hogue stock due to weight and tackiness of the grippy surface sort of sticking to my hunting clothes when moving the gun. I went back to the OEM stock and ground the interferences on the magazine box like I described. Results were accuracy went to 3/8" also.

Hope this helps anyone who is pulling their hair out with M-77 accuracy issues.



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Old December 8th, 2013, 06:46 AM   #2
 
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Right!

Instead of using a Dremel tool I use a small mill file.

All my M77's have loose magazine boxes and a magazine box should not be part of the bedding feature.

Some time ago I bought a new MKII and when I first disassembled I had to use a crescent wrench on a large square shanked screwdriver to back out the forward action screw/bolt. That magazine box was really jammed in there and this only would cause the receiver to be stressed around the magazine box that was acting like some sort of unintended pillar bedding feature. Threaded screws/bolts can exert a huge amount of tension when tightened up, especially 1/4 inch finely threaded ones.
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Old February 11th, 2014, 04:51 AM   #3
 
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I find this very interesting, it's the second time I read comments about a free moving mag box as being necessary for accuracy in these rifles, not stressing the action. It makes good sense to me now that I think about it. I've tightened the action screws a tight as I can on my hawkeye and the mag box is snuggly fixed. I do not recall if the box has ever been loose on this rifle (floor plate has always rattled). I feel like the rifle should be grouping better. I'm wondering how much of the current tension in the action screws is negated by the box obstruction/resistance.

I have a dremel. Roughly, how much material would I need to remove? I am not a big DYI bedding-a-stock kind of guy and didn't buy the rifle just to rebuild it. I believe I can handle a little grinding on the front and rear bottom edge of the box. This sounds like it may be my next step.
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Old February 11th, 2014, 05:21 AM   #4
 
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Good write up!
Thanks for sharing!

My M77 shoots pretty good groups from the factory with handloads ~1" (or less)@ 100yards, so I'm not too worried about mine.
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Old February 11th, 2014, 06:17 AM   #5
 
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Quote:
Originally Posted by BassMan View Post
All my M77's have loose magazine boxes and a magazine box should not be part of the bedding feature.
Mine also have a loose middle action screw.......
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Old February 13th, 2014, 07:55 AM   #6
 
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Took this advice and shaved a little off the small recess along front edge of the magazine bottom with a small mill file. Didn't take much out but now, with the action screws cranked down, I still have a slight rattle to the mag box. I'll let you know how it shoots, if the weather ever clears.
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Old February 13th, 2014, 09:27 AM   #7
 
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Welcome from North Carolina...
Thanks for the tip.
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Old February 15th, 2014, 09:21 AM   #8
 
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Quote:
Originally Posted by Regnitteo View Post
I am a new member to the forum and have this tip that I learned many years ago on accuracy issues with M-77's.
Glad you joined the forum, I'm heading down to the basement now.
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Old February 16th, 2014, 12:54 PM   #9
 
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When you get to the basement use a small mill file instead of the Dremel.

Again the magazine box is not part of the rifle's bedding system. When you complete your careful filing, if done right, the magazine box will move slightly when pushed by your fingers when everything is assembled and tightened up.

The screws/bolts for stock/receiver when tight exert a massive amount of tension probably close to 600's pounds or so when cinched up using a screwdriver with a fat handle.

Best to have the bottom of the action behind the recoil lug and barrel shank to receive all this force than to bend the action around a rigid magazine box acting like a column at the middle of the receiver where it is most flexible at the feed rails.

All this has to be one of the most common sense posts on this forum.

Last edited by BassMan; February 16th, 2014 at 12:58 PM.
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Old February 17th, 2014, 02:01 AM   #10
 
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Quote:
Originally Posted by BassMan View Post
When you get to the basement use a small mill file instead of the Dremel.
Checking the fit, I suspect it may have been a source of my problems with this rifle, a .243. Over time I've glassed the front lug, lapped the bore, swapped scopes, bullets and powders. It started out as a 3" shooter, and is down to about 1/2 that now. At one point, I shot some Trail Boss loads through it and was able to get a couple groups at 50yds that ran close to 1/4", so I know it has a problem I never figured out.

I set the angle on my belt sander to get a square grind, and took off a few thousandths from the bottom, reducing the height. I then polished that with 800grit Emory on a flat hardwood surface. Then checking the fit in the well, I could see some of the problem was a burr standing up where the front section of the trigger was hitting. I removed that with the Dremel. The box now fits with a hair to spare, and can be moved with my finger with all the screws tightened. The fit is close enough to NOT rattle with the floor plate closed. The magazine floor plate works easily and properly for the first time, and everything sits square without a gap between the wood and the floor plate.

I was getting ready to install a pillar on the rear and middle screws, and may still do that, but I'm really curious to see if the box was my problem. As soon as it warms up a bit.

Thanks for your suggestions.

Last edited by TMan51; February 17th, 2014 at 02:03 AM.
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Old February 18th, 2014, 04:08 AM   #11
 
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Regnitteo, Bassman,

Thanks for a great tip. Went to the range yesterday and the new Hawkeye performed much, much better with this modification. Got some really nice groups with different ammo. Night and day difference from earlier range sessions. Now I have complete confidence in the rifle, the only issues are with the guy pulling the trigger. If I do my part this rifle is a shooter for sure.
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Old February 18th, 2014, 11:36 AM   #12
 
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Frustration combined with uncertainty will disrupt concentration and this will have a bad effect on shooting.
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Old February 18th, 2014, 12:52 PM   #13
 
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Yes Sir,

I feel comfortable that I've prepped the gun as well as I can with reasonable effort (solid scope and mounting, appropriate action screw tensioning, file touch up the mag box). I focused on my bench technique, which is very time consuming insuring repeatability shot to shot on a hunt club bench set-up. With the rounded forearm profile, this gun it can be very sensitive to inconsistant bearing on the rest, the only flat area on the bottom of the forearm is a limited spot just in front of the forward action screw. The rifle's reaction to recoil needed to be consistant regarding any movement at the front rest. If a group got a bit erratic I just doubled down my effort on bench technique and groups returned to MOA.

I had no previous experience with Ruger or un-bedded wood-stocked rifles, so I was gettin a little antsy about previous range sessions. I left the range at our hunt club yesterday feeling a whole lot better about this rifle.
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Old February 19th, 2014, 02:07 AM   #14
 
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Quote:
Originally Posted by SCgman View Post
With the rounded forearm profile, this gun it can be very sensitive to inconsistant bearing on the rest.

I had no previous experience with Ruger or un-bedded wood-stocked rifles, so I was gettin a little antsy about previous range sessions. I left the range at our hunt club yesterday feeling a whole lot better about this rifle.
I'm always impressed when shooters manage to shoot 1/2" groups off the hood of their truck over a rolled up sleeping bag.

I have a couple of the Cauldwell Rock JR's. with the rear bags, and the front bags are contoured for a round sporter fore end. It helps a lot.

Glad to see "the cure" worked on your rifle. We're headed for a warm spell, and I just may take Friday off to satisfy my curiosity.
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Old February 19th, 2014, 03:55 AM   #15
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Great tip! thanks
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