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Discussion Starter · #1 · (Edited)
This thread describes the mods I've done to my Mk II F factory stock. This stock is for walking a long way in all weather to shoot things made of tasty meat. I have another wooden stock for this rifle for target work or waiting on a stand.

This stock project has been done a little at a time over the years. The first mod was to add the level bubble almost right after I got it.

I epoxied a chunk of threaded rod in the forearm to stiffen it and that helped, but it still wasn't that great plus it added a bunch of weight.

Next was the semi-adjustable cheek rest that is written up in another thread around here somewhere.



Finally I couldn't handle how flexible this stock was. Rough field positions would get barrel contact even though I had used washers to raise the entire action up and added the threaded rod.

So I got to looking around here and found people talking about adding 3/4 inch aluminum channel for bedding and how it just fits in there for width and I thought why not extend that idea to stiffen the entire stock all the way up to the sling stud?

I used thinner wall square tube instead of the heavier U channel described by others. I did that because I wanted full length stiffness in both flex and twist directions.

My MK II is the older pre-E receiver version so things may be a little different for people now. Also I have the now defunct SSS trigger replacement that was for the pre-Accutrigger models.


Here you can see how I had to remove all of the top and bottom surface of the square tube around the trigger group and also some of the right hand side to clear the safety lever. And you get a good view of the level bubble.


You can see better down into the stock where the trigger would be and you can see the large hole at the top of the tube where the rear mounting stud goes down through. This shouldn't touch. You can also see how the pillar bedding comes up to the bottom of the tube so that there is nothing that can compress when torquing the screws. That bottom hole is just big enough to pass the screw, but not the stud that it threads into on the bottom of the action.


Here is the cutout of the mag well and the front mounting screw. It doesn't show clearly in this shot, but the pillar is tight up against the tube here as well. There was just less overflow epoxy here. Same deal with the hole sizes.


The tube goes all the way up a bit in front of the sling stud. I don't remember now if there was clearance for the back side of that stud or if I drilled a hole in the tube. I did widen the entire inletting front to back just a tiny bit. Mainly this was to get everything rough to help the epoxy since nothing seems to really bond well to this type of nylon.


This shot shows better the entire action area and the holes all along the sides that help the epoxy grab the aluminum. You can see that the side wall of the tube goes farther back on this side.


Here you can see the rear pillar and the mess of JBweld all around it. You can kinda see in the mag well how deep down in the stock the tube sits.


This one blurred out, but you can kinda see with the bottom metal removed that it is bedded to the front pillar.


This shot shows the problem that I'll explain in a bit. Not really so much a problem, but something to keep in mind. That black line on the near side, and that black and light spot on the far side are where I removed so much material that I started to come out the bottom. It made the paint flake I came so close and the light spot is epoxy where I actually came through a bit. Some paint and you'd never know.

Here's how I did all this...

I cut the square tube to the length I wanted and then held it up to the action out of the stock until I had marked off all the places I had to remove. Hacksaw and drill and file to remove the top and bottom of the tube at the trigger and mag well. Then it would sit close enough to really locate the holes. I did double check with the dial calliper. Now I could mount the action to the tube if I wanted. There is plenty of clearance between the bottom of the action and the top of the tube when the mounting studs get to the bottom of the tube. I think this may be different on the newer MK II. Does it have shorter studs?

(This Image is Too Large to Be Displayed Within the Post. Click Link to View) (6351 kB)
That's my action for comparison on trigger shape and mounting studs, etc.

Then I drilled holes all along both sides of the tube for the epoxy to grab.

Next was to use a dremmel type tool with a burr to hog out all the plastic inside the inletting until it was one big long open channel to fit the aluminum tube. That took lots of time and fitting and trying some more. This is where I noticed I was getting too deep in the forearm. I should have stopped removing plastic and cut the bottom face off the tube, but I didn't want to make it into a U channel facing down because that would remove a lot of the twisting strength. I squeaked by, but the pics above show that it was a little too close.

Once I had it all fitted up I drilled big holes all the way through the stock where the mounting screws belong to just accept the 5/8 inch threaded rod for my pillars. I got those roughly made up and then mounted the tube and the pillars to the action with a bit of tape around the screws to center them in the pillars and torqued it all up. I made sure it really did fit in the stock correctly and removed the last little bit of plastic so that it would sit in there to the right depth and not sloped uphill or down from front to back.

With it all taken apart again I filled all the contact points with slower setting epoxy and covered the outside of the tube as best I could while it oozed everywhere and made a big mess. Then I squished it in there and after it started to cure up I used a second batch to make sure all the holes in the sides of the tube were filled and all the other voids as well. JBWeld would have been easier for this as it isn't so runny.

When it was cured I then finished fitting the pillars and JB'd them in including the bottom metal. The fit wasn't super critical for these as the JB filled any voids for the front pillar and the rear pillar is the bottom of the stock at its location. When I put these in I did it with them lightly torqued to the action with the tape as before so that the action would hold them in exactly the correct location while everything cured. I had to use shims to make sure the action stayed centered and straight in the stock. That way I didn't have to be super careful about drilling the holes, I just let the action make sure everything was aligned exactly the way the action wanted it.

When it was all cured I just had to get in there with a knife and dremmel to clean up any interfering blobs.

The stock is so completely stiff now that this mod is complete I could show it to people blindfolded and they would have no idea it was the floppy factory stock. It's every bit as stiff as any rifle stock I've ever handled.
 

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Awesome write-up, thank you!

Questions

Where did you get the aluminum tube, what are its dimensions, and what's it originally meant for?

Approximately how many hours did you spend hogging out the stock and altering the alum before it was ready to be glued in?

What epoxy did you use on the aluminum and stock channel?

I was thinking of adding pillars and some weight to the buttstock, but I may tackle something like this when I have fewer projects going.

Thanks again for taking the time to post this!
 

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Discussion Starter · #3 · (Edited)
The aluminum is just the cheap stuff from the local hardware or box store, 3/4 inch square extruded tube. The wall thickness is about 1/16 inch or maybe a hair less.

I'm not sure how much time I spent on it. I actually did the mod more than a year ago. I would say I had something under 5 hours in that part of the mods, I think maybe 3+. It's hard to gauge since I usually waste a bunch of time looking for that tool that was supposed to be in the shed on the bench but isn't...

I think I tried the epoxy meant for plastic that makes your eyes burn and found it didn't bond as well as the regular 15 minute epoxy. The 5 minute probably won't allow you time to work. I think JBWeld would be the best bet. That's what I used for the cheek riser and was happier with the results. For the aluminum the epoxy is almost as much a mechanical fit as it is actually bonding to anything. That's why I made all the extra holes in the aluminum and roughed up the inlet. This particular nylon is really hard to deal with. I did a huge amount of work and testing to repair a crack in my stock. I've forgotten now what I found from my testing, but it was some kind of nylon and the only solvent I could find for it was formic acid and another acid that had a higher hazard. The repair worked, but solvent bonding wouldn't help with adding aluminum.
 
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