Bedding bottom metal?

[jsthntn247]

Can un bedded bottom metal cause accuracy issues similar to an un bedded rifle? My rifles action is bedded and when I put a magnetic base and micrometer on it without the mag box and follower, deflection is .002 when loosening the front screw and 0 on the back screw. However, with the mag box in deflection when loosening the front screw is .009 and 0 on the back. Which number is the most accurate one to go by?

 

[Dans40X]

Brad,
Is the stock pillared?
If so,shorten the bottom edge(height) of the magazine box .006"-.008" & measure again.

 

[jsthntn247]

Yes, the stock is pillar bedded. What's the easiest way to shorten the mag box? This is a Rem 700 hinged floorplate assembly. Would wet/dry sandpaper work, I used it to take a few thousandths off a shell holder, I would assume it would work for this also.

 

[Dans40X]

Take measurements of the BDL mag box first(fwd/aft end to include lips that seat against underside of bolt rails).
I'd bump it on the belt/disc sander,but hand fitting will work as you only need to remove less than .010".

 

[jsthntn247]

Thanks Dan. Would/Could this cause Poi shifts like a rifle needing bedding?

 

[BoydAllen]

On a BDL it is easy to get the mag box in a bind when installing the bottom metal. There is a lip in the bottom metal that the bottom edge of the box has to fit inside of, and because the back of the box is split, it requires some manipulation during assembly, before any screws are tightened, to get it in place. Without seeing your rifle, it is hard to determine if this is the problem. Generally, with the floor plate open, I want to be able to feel some shifting of the mag. box when I reach inside press my fingers against the inside of the box and try to move it up and down. I don't need much but I do not want it jammed between the action and the floor plate. I would make sure that I had it inside the recess in the floor plate before shortening the box. If this is not right, the best bedding job in the world will not overcome it. Also, bedding the floor plate against the bottom of the pillars is a good idea. With the barrel floated, and the rifle horizontal, the weight of the barrel is trying to pull the back of the action up, and the only thing that keeps it securely against the action bedding is the back of the bottom metal/trigger guard which is pulled up into the stock by the weight of the barrel. This makes the fit at this point of concentrated force an important contributor to the quality of the total bedding system.

 

[BigDMT]

Yes, the stock is pillar bedded. What's the easiest way to shorten the mag box?

Use a bench grinder. You don't have to be perfectly precise when removing magazine metal. Just have to take enough off where you know it is not pinching between the action and the bottom metal. And YES, that can definitely cause accuracy and POI issues with a rifle.

What you are experiencing is a very common problem with Ruger M77 rifles and it does affect their accuracy. Many times the magazines have to be ground down a considerable amount to get them free floating.

I know this may be a stupid question; But by chance was the rifle originally a 700 ADL that you converted to BDL?

 

[jsthntn247]

No, It was a Sendero that I rechambered and put in a Manners T-5. Without the mag box in, the action screws tighten very quickly like they should when properly bedded. With the mag box in it takes several turns to tighten and I can feel it pulling down.

 

[jsthntn247]

On a BDL it is easy to get the mag box in a bind when installing the bottom metal. There is a lip in the bottom metal that the bottom edge of the box has to fit inside of, and because the back of the box is split, it requires some manipulation during assembly, before any screws are tightened, to get it in place. Without seeing your rifle, it is hard to determine if this is the problem. Generally, with the floor plate open, I want to be able to feel some shifting of the mag. box when I reach inside press my fingers against the inside of the box and try to move it up and down. I don't need much but I do not want it jammed between the action and the floor plate. I would make sure that I had it inside the recess in the floor plate before shortening the box. If this is not right, the best bedding job in the world will not overcome it. Also, bedding the floor plate against the bottom of the pillars is a good idea. With the barrel floated, and the rifle horizontal, the weight of the barrel is trying to pull the back of the action up, and the only thing that keeps it securely against the action bedding is the back of the bottom metal/trigger guard which is pulled up into the stock by the weight of the barrel. This makes the fit at this point of concentrated force an important contributor to the quality of the total bedding system.

Boyd, when bedding the bottom metal, should I put the bedding material on the rear action screw area and tighten the front down similar to bedding a scope base?

 

[BoydAllen]

I would put some bedding compound in the areas of the front and rear screws, with the rifle supported upside down, probably with a barrel vise clamped to the barrel, but not to the bench, with everything blocked up so that the vise kept the rifle roll stable and supported the barrel, and a scope base supported the action with a spacer at the back between it and the bench. Put release on the floor plate, and anything else that you do not want bedding material on. Start the screws and tighten them just enough so that you have alignment, but not tight, and let it fully harden, before cleaning things up. Be sure to clean out the screw holes when you finish. The action screws should not make contact with the inside of the pillars anywhere, or even come very close. They should only make contact at their heads and in the action threads, and not the bedding.

 

[jsthntn247]

Looked at some more tonight. The mag box was was not setting in the stock grove and was causing it to bind, when this happened my deflection numbers were high. When I got it to set right in there the bottom metal would still bend when torquing the screws but I could wiggle it some and deflection was under .002. I bedded it the way Boyd said, don't have a good feeling about it but I'll know in a few hours.

 

[BoydAllen]

What is it that worries you? I am glad that you found the magazine bind. I was passing along something that a local gunsmith showed me years ago. I would bet that there are considerable numbers of BDLs that suffer from the same magazine problem that you had.

 

[jsthntn247]

I've been recently getting poi shift with this gun and never have before. I did take it out of the stock while back and am assuming I put it back together with the magazine in a bind causing my issuies. Pulled the floorplate out and the bedding actually looked really good, it doesn't bow any more when tightening down. Hopefully this solved my shifting issues. Thanks, fellas.