Tapering Stepped Barrel and Fixing Barrel Channel in Stock

[mrh477]

Perhaps this would be better as two posts but I figure someone with the expertise to answer one of these questions may be able to answer the other. Both are in regard to a Mauser sporter I'm building.

First, it's got a stepped military-style barrel (Kongsberg I believe, .30-06) and I want to look into tapering one of the steps down so that it essentially turns two steps into one. There are 3 total and all are tapered a little already but the transition between the second and third step is small and I think it would look much nicer if the step itself was eliminated. Pics show the last step that I'm talking about. Would it be a costly process to have that second step tapered down to make a smooth transition?

Second question is in regard to the barrel channel. It appears this stock was originally made for a barrel with one more step, like the original Mauser military barrels, so with this barrel there is too big a gap (pictured) in part of the channel. I will be bedding the action so one option is to fill the extra gap with bedding compound but I think it would look nicer if I could fill that gap with walnut to basically make it disappear. I've fixed cracks before using the common method of mixing wood glue and sawdust so I'm considering this method. Issue is I'll be staining the stock then using a tung oil finish, so I worry that the glue/sawdust mixture won't take stain or finish well and will stick out like a sore thumb. It still might be better than bedding compound which I know will stick out like a sore thumb though. Thoughts?



Thanks!

 

[Kp321]

A good machinist could taper your barrel and eliminate the steps for about what a new sporter barrel costs or maybe a little more. Seriously, it takes lathe time to taper a barrel which equals $$$. You can draw file the barrel by hand then polish the resulting small flats with emery cloth shoe shine fashion. Takes hours! What is your time worth? I have lived with stepped Mauser barrels all my life and have had some very good shooters.
The extra step on your stock was made for the rear sight sleeve which is not present on your barrel. Brownells includes some brown dye in their Acraglas kit to match the epoxy to the stock color. Stain and finish your stock then mix the Acraglas with the brown dye to match the stock color. Properly done it will be virtually invisible. Be sure to use plenty of release agent!

 

[rcmodel]

I don't recommend it.

Tapering a stepped military barrel in a lathe creates heat, and often unlishes internal stress's that makes the barrel get real Squirelly when it heats up.

And a straight taper deep enough to take out the steps will leave the muzzle paper thin.



1. I'd either leave it be, and the stock will still fit. (Looks fine to me.)

2. Or re-barrel it with a stress relieved new tapered barrel like you want.

If you decide to leave it stepped it will fit the stock.

If you rebarrel it the stock will have to be inletted to fit the new barrel.

In either case, Winner!!

rc

 

[Jim K]

It seldom applies to a hunting rifle, but FWIW, those steps are there to allow the barrel to expand when hot without changing the zero.

There is an easier way to work the barrel down, and that is to put it in a lathe and run a hand-held belt sander against it as it turns. Change the belts from coarse to fine as you go and the result will work OK.

Jim

 

[rcmodel]

Still gonna leave a mighty slim barrel at the middle & muzzle end before you get the last traces of the steps out.

I still think it's a bad idea.

Never worked very well for me in the past.
So I stopped doing it about 45 years ago.

rc

 

[mrh477]

"There is an easier way to work the barrel down, and that is to put it in a lathe and run a hand-held belt sander against it as it turns. Change the belts from coarse to fine as you go and the result will work OK."

Jim, that's the kind of solution I had in mind.

RC, I think you are confused as to my exact intentions. My apologies for not explaining it clearly. I don't intend the create a perfectly straight taper all the way through both steps because the end of the barrel is about .650" or less and I don't want it to be any thinner. So the idea is to just taper part of that 2nd to last step in order to get rid of the sharp transition between the steps. So in the end the barrel will look like it just has 2 steps instead of 3. The last and second to last steps are close enough in diameter that I think getting rid of the transition without creating an exactly straight taper won't be noticeable.

My main concern is just that I can grind off that much metal with a belt sander or on a lathe without damaging anything. Keeping it cool enough shouldn't be an issue but I was worried about bending or some other complication that an amateur like myself may not even know of.

 

[Fred in Wisc]

I'd use epoxy resin and wood flour to fill that gap. Wood flour is super fine sawdust, with a much smoother texture. I usually buy it from bateau.com, a pound is about $5 or $7 and will probably bed all the guns you ever own. Epoxy is extremely environmentally resistant once cured so it'll last forever.

Do some research on release agents so you don't glue the barrel to the stock forever. For a "one off" that's good but not perfect, mask the metal with 3M Super 33 electrical tape, it releases from epoxy quite well, is super thin, easy to use, and available at your local Ace hardware.

 

[Jim K]

It is better, if possible, if the "wood flour" comes from the stock itself. Usually, enough can come off (or has to come off) the stock that getting enough fine dust is easy and it will match the wood.

Jim

 

[mrh477]

Would an epoxy resin be preferable to wood glue?

As of now the plan is to see if I can plane some walnut strips thin enough to glue in there because that would definitely look best but if I can't get that to work then sawdust and glue is the backup plan. I also have a couple little gaps where the action was inletted poorly so either way I'll give the sawdust and glue method a shot.

Would an epoxy resin be preferable to wood glue? What epoxy is best?

Thanks

 

[rcmodel]

Yes, epoxy is very much preferable.

It doesn't 'dry' like glue, it cures chemically.

So there is zero shrinkage like with all water or solvent based glues.

rc

 

[mrh477]

Thanks for the help, fellas. Jim K and RC, it seems like just about every gunsmithing-related question (and I have plenty) I've posted ends up involving answers from one or both of you. I really appreciate all the advice you have given me.

Now, with that in mind, here's the next one. I'll be polishing the bolt and extractor at some point so I got the bolt out yesterday just to inspect it and get an idea of what it's gonna take. I know not to touch the back of the locking lugs or any cam surfaces but I'd like the bolt to have a uniform finish. Problem is the bolt (and the raceways on the action for that matter) is covered in fine pitting that is going to take a decent amount of sanding to eliminate. Will I damage any heat treating, hardening, or tolerances by sanding all this pitting out?

I'm particularly worried about the raceways. Being an old Mauser, the action is already pretty loose so I worry that if I sand all the pitting out of the raceways it'll be sloppy as hell.

Thoughts?

 

[rcmodel]

I have polished 03 Springfield and every kind of Mauser bolt and extractor with no ill effects in the past.

The extractors are hard clear through springs.

The bolts I think? are differently hardened in different places on the better ones.

So no, I wouldn't be concerned about polishing off a case hardened surface finish.
(And you already know to stay off the locking lugs and cam surfaces.)

As for increasing 'Sloppyness'?
Yes, you will increase tolerances if you sand off a lot.
(But, they aren't known for no slop in the first place! Slop is good on a military action that must have room to keep on ticking when full of mud or sand.)

Two alternatives?
1. Bead blasting the bolt to hide the pits won't change a thing, and give you a soft satin finish that will hold oil well.
2. Engine turning (sometimes called Jeweling) will mask the pits from being so noticeable.

The problem with either method is, normal wear from operating the bolt will still leave longitudinal scratch marks on the shiny surfaces that will be just as unsightly as the pitting was in the first place.

You could just rough polish the bolt and blue it like Mauser's often were, and be done with it.



PS: Thanks for the compliment.
But I learned a lot of things I didn't know from Jim K, and others here on THR!!

There is a major gun knowledge Brain Trust here on THR.
And it's not just him, or me by any means!!

Pretty sure Jim K would agree with me, but I didn't ask him first!!

rc

 

[Jim K]

I also thank you for the kind words. I did not use a lot of bead blasting, but I definitely do NOT recommend engine turning unless you plan to put the gun in a display case with nice soft lighting.

The reason is that the bolt moves in the receiver (duh!). And every time it does, the contact with the receiver cuts through that nice engine turning and removes some of it. The result, IMHO, is that after a few shots the gun looks far worse than if the bolt had merely been polished. I used to try to talk people out of engine turning, though it was a money-maker with little cost except labor. But it is a tedious job, and I know of no automatic process for a small shop. It is a matter of turn the crank, pull the drill press handle, turn the crank, etc. PITA.

Jim

 

[mrh477]

So recent experience has taught me that hand sanding a barrel is a pretty tedious job...

Since I don't have a lathe myself I thought initially I'd experiment with my belt sander and see if I could pull this project off myself. I was able to remove the step pretty easily while leaving a mediocre finish by carefully turning the barrel on the belt sander so that it was never held steady in one place. However, even with me being as meticulous as possible in keeping the barrel level and turning it at a consistent rate, I still ended up with some waviness that would require a lot of hand sanding to eliminate. I'm talking hours of hand sanding. Not worth it to me! So in the end I took it to a machine shop and it took the guy less than an hour to taper the barrel and leave a great finish on it. Moral of the story, cough up the cash and go to a professional unless you're willing to spend hours hand sanding a piece of metal.

I do like how the barrel looks with the step removed so it was worth the money in my mind.

First pic is after the machine shop, second is after the initial belt sanding session. Pretty big difference.

 

[boom boom]

Brownells sells a bolt receiver way polisher if that is what you want for about $50. It looks like a tuning fork and holds the emery cloth while you work it in and out of your receiver and serves to keep the polishing even. I believe Midway used to sell a clone but doesn't anymore.

http://www.brownells.com/gunsmith-t...iver-tools/receiver-way-polisher-prod395.aspx (it is 53.95).

 

[mrh477]

Brownells sells a bolt receiver way polisher if that is what you want for about $50. It looks like a tuning fork and holds the emery cloth while you work it in and out of your receiver and serves to keep the polishing even. I believe Midway used to sell a clone but doesn't anymore.

http://www.brownells.com/gunsmith-t...iver-tools/receiver-way-polisher-prod395.aspx (it is 53.95).

Ya I saw that but for $50 I think I'll make my own out of wood. Shouldn't be too hard.