# Ruger M77 - zero shift with hot barrel - update



## returntoarchery (Jan 2, 2009)

Ok my old 1973 Ruger M77 .270 Winchester has started shifting the zero 2+ inches right and 2+ inches high from a cold barrel to hot barrel. Takes only 2 - 3 shots for the shift to occur. The action is glass bedded and the barrel is free floated. I've shot sub .5 MOA with it and don't recall this behavior before. The scope rings have been lapped and aligned with the Wheeler scope ring lapping/alignment kit. Everything is nice and tight but not over tighten.

Any ideas what to check next?


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## Hammack (Jan 2, 2009)

Is the barrel nice and clean?  It's not uncommon for POI to shift with a hot barrel.  Especially with sporter weight barrels.  Is the first shot from a cold barrel consistent?  Does the shift occur the same everytime?


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## Carpathia (Jan 2, 2009)

returntoarchery said:


> Ok my old 1973 Ruger M77 .270 Winchester has started shifting the zero 2+ inches right and 2+ inches high from a cold barrel to hot barrel. Takes only 2 - 3 shots for the shift to occur. The action is glass bedded and the barrel is free floated. I've shot sub .5 MOA with it and don't recall this behavior before. The scope rings have been lapped and aligned with the Wheeler scope ring lapping/alignment kit. Everything is nice and tight but not over tighten.
> 
> Any ideas what to check next?




I'd guess that the barrel is not as free floating as you think it is. It's not unusual for a wood stock to warp slightly or a cheap synthetic.


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## returntoarchery (Jan 2, 2009)

Hammack said:


> Is the barrel nice and clean?  It's not uncommon for POI to shift with a hot barrel.



Occurs whether the barrel is squeakie clean, i.e. absolulty no copper fouling, or not.



Hammack said:


> Especially with sporter weight barrels.



Yep it's a light weight barrel all right. Just puzzling the heck out me now that is't started so sudden.



Hammack said:


> Is the first shot from a cold barrel consistent?



Yes.



Hammack said:


> Does the shift occur the same everytime?



As far as I can tell.


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## returntoarchery (Jan 2, 2009)

Carpathia said:


> I'd guess that the barrel is not as free floating as you think it is. It's not unusual for a wood stock to warp slightly or a cheap synthetic.



My first thoughts as well. Checked it at the range while the barrel was hot and there was no contact. Dollar bill passed freely from foreend tip to the receiver.


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## GA1dad (Jan 2, 2009)

Try taking the stock off, and then re-installing it. Tighten the forearm screw first, then the one near trigger. Shoot and check results. See if it changes at all.


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## returntoarchery (Jan 2, 2009)

GA1dad said:


> Try taking the stock off, and then re-installing it. Tighten the forearm screw first, then the one near trigger. Shoot and check results. See if it changes at all.




Good  idea.


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## returntoarchery (Jan 20, 2009)

GA1dad said:


> Try taking the stock off, and then re-installing it. Tighten the forearm screw first, then the one near trigger. Shoot and check results. See if it changes at all.



Well the plot thickens. Yesterday I removed the stock. Checked the glass bedding and barrel free float. All looked good no crushed areas and free float has plenty of clearance. As suggested tightened the main/front recoil lug action screw first then tightened rear action screw then the tang screw. Cleaned the barrel thoroughly. Now the dang thing is doing the exact opposite. Shoots high right when cold and low left when hot!  

Only thing I can think of is the action is torquing somehow, maybe need to invest in a inch pound torque wrench to precisely tighten the action screws, or scope mounting is off some how. I used new Burris Rings and lapped and aligned them with the Wheeler Scope Lapping and Alignment kit.


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## ScottD (Jan 20, 2009)

Sounds like a bedding problem.  Here is a couple of ideas.

Maybe the glass bedding is thin enough that the stock underneath has warped.  May need to rebed.  paint the action with some prussian blue - reassemble - disassemble and see if it looks even.

Try removing from the stock again - tighten in the same procedure  except only snug up the tang screw.

Also - check the recoil lug area - only the sides of the recoil lug should touch the bedding - if the bottom of the recoil lug is touching, it can cause what your describing.  If it is touching - take some material out of that area with a dremel and try again.

Loosen the  actions screws & rings set the gun outside and allow to chill.  Tighten everything cold & shoot. Remember it has been 30F outside - maybe the extreme cold is the issue.


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## returntoarchery (Jan 20, 2009)

Good ideas.

May be the recoil lug bedding as I'm sure it's touching on the bottom. I'll check that area. Yeah thought about rebedding it. I'm a lot wiser now than when I did the original bedding 30 years ago so I'm sure I'll do a better job now. 

Wish it was only in the cold. At least one time when at the range it was 70 degrees and still was showing POI/Zero shift. 

appreciate the imput.


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## germag (Jan 20, 2009)

I'd throw some pillars in it and rebed. That will eliminate the problem of torque on the action screws causing issues.


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## ScottD (Jan 20, 2009)

If / when you rebed - put 2 or 3 layers of masking tape on the bottom of the recoil lug.  None on the face..leave it raw.

Then after bedding - just remove the tape.  The idea is to prevent a see-saw action when you tighten the action down into the stock.


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## NottelyBILL (Jan 20, 2009)

I agree with germag- needs pillars or tighten the screws with a torque wrench. My model 7 will move if I do not tighten it down exactly the same torque but it is not bedded nor does it have pillars. But when torque properly it goes right back to the same place on the target. Both my 700's have pillars and I do not use a torque wrench on them and they are ok.


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## returntoarchery (Jan 20, 2009)

germag said:


> I'd throw some pillars in it and rebed.



Was thinking that very thing as I was at brownells  site looking up a pillar kit - which they have for the M77.



ScottD said:


> If / when you rebed - put 2 or 3 layers of masking tape on the bottom of the recoil lug.  None on the face..leave it raw.



Good idea. Didn't think of that.

Next bedding question. I've seen some bedding where there is an inch or so of bedding under the chamber end of the barrel, supposedly to support the barrel, and the remainder of the barrel is free floated. Good or bad idea?


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## jglenn (Jan 20, 2009)

I've always bedded the first 1-2" of the barrel in front of the lug.

try digging out the bottom of the lug glass bedding and then DON'T tighten the small middle screw much at all. I've always used a good bit of locktite on this screw and just tightened it up firm not tight at all.


also take a VERY close look at the front of your barrel for any nicks around the rifling


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## GA1dad (Jan 21, 2009)

Glad we could help you at least find the problem. Sorry we can't fix it for you over the internet.


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## returntoarchery (Jan 21, 2009)

GA1dad said:


> Glad we could help you at least find the problem. Sorry we can't fix it for you over the internet.



Hey why not!


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## germag (Jan 21, 2009)

If you put the pillars in, you'll need a 9/16" counterbore with a .262" pilot.


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## returntoarchery (Jan 21, 2009)

germag said:


> If you put the pillars in, you'll need a 9/16" counterbore with a .262" pilot.



Thanks. That's what I'm gonna have to do as well as rebed it. I checked the bedding with candle black and the bedding is uneven and has pressure points on bottom left side of the action before and after the recoil lug.  Can't get any good work out of a 20 year old diy gunsmith (me)...   

I dremeled out the bottom of the recoil lug and tightened the main screw first moderate pressure. As suggested I used blue loctite on the rear and tang screws and only snugged them up. Went to the range and the shift cold/hot poi shift is there there but not a bad.   I'll do until can rebed the action and install pillars.

Now that I think about it the shift got worst when I started tightening down the main screw really tight  thinking was my problem. I was only making it worst with the sloppy bedding.

Thanks guys for the suggestions and help.


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## jglenn (Jan 21, 2009)

it's ok to tighten the rear screw but it's the small middle screw that can give you issues. That's the one that I use locktite on only


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