Re-Rifling

[farmall]

Deep thinking or silly-ness...you decide.

Surplus barrels are readily available and you can only have so many 8mm's (theoretically).

Why couldn't a broach or button be made that would re-rifle an 8mm to something bigger (.338 for instance)? The existing rifling could be used to impart the twist.

You'd only have to shave off .015" to go to .338.

Maybe deepen the grooves first and then use them as a guide to rebore the lands...vs. the "regular" barrel making method of boring first, then rifling.

I'm thinking about something that you could do at home...cheap.

Cheaper than a than a barrel vice and action wrench?

Cheaper than a new barrel?

Hmmm....

 

[z1r]

Good reboring costs about $265 + up. Most folks tell me there is a minimum step up in size required to clean out the existing markings and or stresses imparted to the barrel. Most would not go from .323 to .338. I know of one that will.

 

You could do it provided you have the right tools. There are books out there. It would be cost effective if you could do it yourself. Otherwise, it is generally cheaper just to rebarrel. About the only thing that justifies the cost of reboring is if the original barrel is unique like an octagonal or integrated rib or some such.

[Guest MorgansBoss]

Farmall

 

I think I know what you're talking about - not the established proceedure but something totally "out of the box" in terms of methodology. Am I right? I'm certian it would require a good lathe and some creative tooling at the very least, and of course it would still entail re-chambering. Add to this the fact that most mil-surp barrels are pretty thin to start with and I'm not sure the possibilities would be worth the effort and investment, what with decent after-market barrels available so cheaply and readily.

 

HOWEVER... being cost effective aint necessarily what this hobby is all about is it? Three-forths of the interest is in learning and doing for yourself. If so inclined I say figure out what it'd take. Who knows, you just may come up with something that'll make you some money!

[Doble Troble]

Very Cool Idea. Maybe a series of piloted hammer-driven broaches would work. Each one would remove only a small amount of material following the rifling as a guide for twist. The pilot would keep it true. There'd probably be some chatter, but that's what lapping is for.

 

You'll need a lathe, mill and a dividing head to make the broaches - that would be the hard part.

[farmall]

Morgansboss,

Yep, you caught my thinking...

 

DobleTroble,

You caught it too.

 

I was thinking about a disk of carbide that had the new rifling (grooves) cut on a wire EDM (or ground). It would also have a keyed hole (square hole?) for a pilot/mandrel. The pilot/mandrel would be a piece of material softer than the barrel (but tough) that would lock into the carbide and spin with the existing rifling. You could probably pull it through with a come-a-long and a thin piece of cable... Better yet - use one of those soft cable crimp things as a means to fasten the button to the cable AND impart the spin (squish into the existing rifling)...

 

Hmmm...I probably need more stuff to do at work...

[mimic]

One thing that was bugging me about this idea, then I thought of it. The recommended twist rate for the 8mm is 1 in 9, where the recommended rate for the 338 is 1 in 10. Now I'll admit that's not a huge difference, but it could be signifigant if reloads are being used, and it's just enough of a difference that it blows the whole idea of using the existing rifling grooves out of the water.

 

 

Mimic

[z1r]

I doubt you'd notice the affects of a slightly over stabilized bullet in .338. Besides, it would likely be somewhat beneficial if you felt like loading up some long 300's.

[tinkerfive]

Farmall

 

I don't recall if I posted it on the other board last year when I had the same idea of

taking an 8MM and going to .357 for a 35Wheelen.

 

I kind of like the come along idea. I never liked the idea of push rods to drive the

broach.

 

Actually I was thinking a two broach (two step) process might work best.

 

Broach #1 has 8MM pilot and cuts the grooves to the proper depth ( .338 / .357 ).

Broach #2 has pilot of the new cal grooves and cuts the lands behind it.

 

The two step process both cuts the cutting force in half for each pass and allows

for easier handeling of half the amount of cuttings per pass.

 

Only experimentation would necessarily prove it, I was wondering if a series of

broaches steping up in caliber would work better. For instance to get to my .357,

would it be better to cut your .338 first rather than going directly from 8mm to .357?

 

Tinker

 

PS

Man If you can figure how to fabricate the broaches, I'd be glad to work with you

on it.

[carzngunz]

I've been reading these posts and I've got to tell you I really like this idea.

 

One thing to keep in mind though is that a broach requires a lot of force and will probably need to be made so as to be adjusted in fine increments. You will not be able to generate much force with a come-a-long so you would probably want to keep your cutting depth to a couple of thousandths per pass.

 

As for the lands, why not just use a piloted reamer? If the grooves were centered with a pilot then opening up the lands from the same center should work as well. You could probably use a machine reamer and modify it and add a pilot. It might save a little work over fabricating something from scratch.

 

I'm just throwing out some ideas but I would love to see if this could be made to work. Keep us all posted. Scott

[rebel49]

The one thing to remember with carbide is that it is brittle, even the more dense grades. Also it is in the 70-72+ RC range for hardness, so a razor sharp edge will chip very quickly. This will happen more so when you try and move it slowly like you are talking about. Most button rifled barrel the button actually forces the metal out rather than cutting it. What's needed is something along the lines of M4 tool steel hardened to 65RC and coated with Titanium Nitride for wear and toughness after sharpening. Even then you run a very good chance that somewhere down the barrel it will try and track out of the existing rifleing and try cutting a new path. It would be cheaper and less work to buy a rifled blank and turn a new barrel by the time you make the necessary 4-6 cutters, pilots and mandrels. Just my $.02 and thoughts as an old tool & die maker.

Rebel49

[z1r]

It would be cheaper and less work to buy a rifled blank and turn a new barrel by the time you make the necessary 4-6 cutters, pilots and mandrels. Just my $.02 and thoughts as an old tool & die maker.

 

Which is why the guys that do this charge better than $265.

 

If there were an economical way to do this we'd be able to buy surplus barrels that have been rebored or re-rifled.

[tinkerfive]

Farmall

 

I think we have the seed of a good idea here.

 

I'll choose to continue the discussion and explore the possibilities.

 

If it doesn't pan out , well so be it. So gents if we can avoid the ' it can't be

done (reasonably)' comments and keep the ideas flowing; that would be great!

 

Glad I got that off my chest!!

 

Rebel49 & carzngunz had some great comments.

 

I was also concerned about the force needed to cut the grooves.

I was wondering if rather than actually cutting the grooves if they might

be honed. In this case the pioletd broach might have the diamond dust

coated material rather than carbide cutters. The 'cutters' then might have either

a spring loaded mechinsm or a turn a screw to adjust mechinism for each pass.

 

I like the idea of a pioleted reamer to cut the lands.

[Doble Troble]

Even if it doesn't turn-out economical you guys will be learning a lot about barrels, rifling, broaches and reamers.

 

And what's that worth relative to the cost of a barrel?

 

 

Keep it up guys. If it were'nt for crazy ideas, we'd still be using stone tools.

 

[Jimro]

Not to sound negative, but pulling a broach cutter through a long rifle barrel will leave the steel chips in front of the broach cutter where it would build up and bind the tool. Maybe by pumping oil to remove the chips?

 

But broach cutting is inherently inacurate, which is why only short pistol barrels are made with broach cutters, so broaching the grooves out to .338 will probably not make a very accurate rifle, no matter how perfectly the lands are reamed or cut to .330. Lapping would help, but lapping is an art, not a science.

 

I think that a better way is the old fashioned way, use a lathe to machine out the lands and make a smoothbore .323 barrel first, then use a reamer to ream to .330, that's only 3.5 thousandths difference in radius, pretty tight. Then find a source for a .338 button reamer, then heat treat the barrel to relieve the stresses induced by the rifling process. Cut rifling does not stress the metal, but making a cut rifling machine is a whole nother project.

 

This requires deep drills of appropriate size, an oil pumping and filtering system, finish reamer of appropriate size, and a rifling system. No wonder they charge so much for reboring. If you could make your own deep drills and reamer that would cut down on price.

 

Reboring sounds like a definate project for a guy with a shop and plenty of time on his hands.

 

Jimro

[z1r]

Farmall

 

So gents if we can avoid the ' it can't be done (reasonably)' comments and keep the ideas flowing; that  would be great!

 

 

3195[/snapback]

 

Just think of it as inspiration. It ought to be fun to prove me wrong.

[Guest Guest_JBMauser_*]

I have been hatching similar ideas as to those proposed here. The thing I find interesting is that men cut rifling outdoors in the backwoods without a lathe, but with jigs made of wood and built and rifled Pennsylvania Long rifle barrels one at a time. It can be done. It has been done. I have a sewer pipe krag barrel that could become an 8mm/40 ...?? maybe.. JB

[farmall]

Well fellas, I appreciate all of the input. I'm also attaching the (edited) emails between a good friend/toolmaker and me.

Farmall: Can it be done so that the "do it yourselfer" can do it (someone without a bunch of expensive equipment)?

Hands (Toolmaker): No! It can't be done simply. If you think of it as a press fit situation you'll realize that a .014 press fit on that small of a dia. would require

you to put the "cutter" in liquid nitrogen and heat the barrel to get it

started. Then when the temperature equalizes part way down to bore you'd

wind up with one piece of steel. The only thing that I think might work

would be your idea but instead of a cutter use progressive lapping. Also, if

you want to try it...buy more life insurance.

Farmall's reply question: What if you had 14 cutters taking .001 at a time? You think they'd follow the existing rifling (and then the newer rifling for cutters 2 through 14)?

Hands (Toolmaker): ..just get satisfied with the 8mm bullets available or re-barrel... After you go through all this work the accuracy would be so bad I'd stand in front of the target with out any fear...

 

To sum up...like most things, it looks good on paper, but actually doing it would be pretty tough. Rebel49, Jimro, Z1R and Hands have made the main points clear: chip load problems, tool material issues, tracking the old rifling issues, lousy surface finish, cheaper & better to get a new barrel (unless you just happen to have the very expensive and specialized equipment at your disposal).

So...I'm gonna move on to one of the many other idle thoughts that are swimming around in my head. Thanks. Farmall

 

[Doble Troble]

I still bet it would work .

[Guest Guest_BENNYPAPA_*]

As far as the guys making gun barrels with hand tools all those years ago....

They were soft steel or iron barrels shooting soft lead balls with cloth or leather patches. There is a LOT of give in the patch/ball to squeeze past any irregularities when compared to modern bullet/barrel fit tolerances.

 

Apples and Oranges I am afriad.

 

 

I see one theoritical obstacle.

 

If the original bore is bad enough to mandate resurfacing you cannot rely on it as a guide surface for a piloted cutter or your resulting cut will be flawed as well.

 

I'm not giving up on the idea, not down on it at all.

 

Now, IF the grooves are reliable as guide surfaces, Why couldn't you use an adjustable cutter like a rifling cutter? Cut one groove larger at a time. Only problem I see is making the system free-rotating enough to follow the grooves. (Or if the grooves aren't a reliable guide surface due to pitting)

 

It does appear that reboring/rerifling is the most reliable way to go about it. It is quite a setup too. A previous post mentions the forced coolant/chip removal system setp up on a boring machine(lathe). Then there is the cutters/bits... Quite a setup.

 

If life allows enough time and funds, I will add this setup to my lathe one day so don't think that expense and lots of manhours is any kind of discouragement.

 

If I had a steady rest and coolant system already, I'd say let's get together on this. I love the idea of reboring worn out barrels, especially when they are so plentiful but, I am not setup for it.

 

 

I love it that there are other people that are not so ingrained into the throw away society that they too think of these things.

 

Thanks for the thread. I have enjoyed all the great thoughts and discussion.

 

Bennypapa

[BobVZ]

I have a 1916 Spanish short rifle in 7x57 that has a either a soldered in or shrink- fit/pressed in barrel liner. This practice is described in Olsens Mauser book. Close examination under magnification reveals it to be a rather thin-walled(1mm) tube that lines the barrel from breech to muzzle. There is no solder line visible, so I am leaning to the pressed or shrink-fit theory. I can only theorize that the barrel and chamber were overbored by 1mm and this insert prepared and pressed in the heated barrel.

 

Provided this technology could be resurrected, might this be an option for some of these worn out barrels?I wonder what the cost would be compared to a re-barrel or re-bore?

[riceone]

I have talked to a couple of places that re-line barrels. I have a 30-30 that I would like re-lined to 25-35. The cost I have been quoted is $250 to $300. The reason I am inclined to re-lining instead of re-barreling is I would like to keep the vintage look of the old barrel. I do a lot of odd and hard things but looks like re-rifling would be very very difficult for all the reasons stated. riceone.

[Doble Troble]

Maybe it would be easier (OK, cheaper, definitely not easier) to order a new barrel and finish it to look old.

 

It MIGHT shoot better too.

[AzRednek]

I have a 1916 Spanish short rifle in 7x57 that has a either a soldered in or shrink- fit/pressed in barrel liner.

3630[/snapback]

 

 

BobVZ you might have a collector's piece!! Many of the re-lined barrels were done for the Franco govt by the Nazis. Remove the action from the wood and look on the bottom side of the action for a very tiny Nazi stamping. Unless you have excellent eyesight you will likely need a magnifying glass. I've previoiusly had two, one was spray painted presumably in the refurb operation and the tiny eagle and swastika mark was hard to find. Nazi collectors are a strange bunch and tend to trade down when horse trading non WW2 goods for anything with a swastika on it. About 25 years ago I managed to trade one for an M-1 Carbine with a damaged stock.

 

When I first discovered nazi stamp I took it to a meeting of the Arizona Gun Collectors. They were having a stump the experts night. I didn't fool anybody as two Mauser collectors were aware of the process and nazi stamp. The following month's meeting one of the collectors showed it to me in a book. Sorry but I don't recall the name of the book.