Switch Barrel Mauser?

[leadman]

I have a 1893 Spanish Mauser that has a very worn 7X57 barrel on it. A 175gr Rem bullet is barely in the case to almost touch the rifling. Cast is minute of 55 gallon drum.
I have a 7.62X39 barrel and feed kit on the way. I also have a '98 Mauser barrel in 25-06 in the garage. This could become a 257 Roberts.
I got the idea for part of this when talking to a guy that rebarreled benchrest guns. He said the barrels do not necessarily needed to be cranked way tight.
I was thinking of installing the barrel and checking headspace and doing what was necessary there, then putting a witness mark on the action and barrel. Mark the barrel for milling flats just in front of the action for an open end wrench. Then reinstall the barrel and drill a hole at the front of the action on the bottom that just goes into the barrel for a setscrew.
A Leupold type sight base would be installed on the action. A scope would be sighted in and one of the windage screws loctited in place. Then if additional barrels were fitted in the same method a scope could be installed and sighted in for the barrel.
To change a barrel you would remove the action, take out the setscrew, turn out old barrel, turn in new barrel, change mag spring and follower if needed, tighten the set screw, change the scope, install in the stock.

What are the flaws in my plan?

[Frank46]

Head space comes to mind. You would have to have your bolt to have the proper head space for each barrel you plan on using. I would also use molycote or a similar lubricant (neverseize) to prevent easy installation and removal of the barrels. Either one will prevent galling and seizing between both the threads in the barrel or receiver. Don't know where you'd get the molycoat but never seize should be in just about any auto parts store. Bench rest shooters do not torque their barrels like you find on old mausers. They use an aluminum barrel holder and a tool also made out of aluminum. Back end of the tool has a square machined on it and the handle fits over this square to provide the necessary torque to unscres the barre. Reid Coffield of the shotgun news did an article last year on swith barrel mausers. Hope this helps. Frank

[leadman]

The same bolt will (should) work with the 7.62X39 and the 257 Roberts so as long as each barrel is headspaced properly that should be ok.
I have lots of antiseize, was a diesel mechanic in Michigan for many years. I also have spray graphite that is a very good dry lubricant.

I'll have to see if that article is on-line.

I had an old Mauser rebarreled by a locate gunsmith and it started seperating cases at the range one day. I found the barrel had come loose and unscrewing. I hand tightened it and shot some more with no problems. I did buy the tools and tightened it later though.

I was thinking about this project last night then read a post on a local forum about the new T/C Dimension switch barrel bolt rifle. The concept is pretty neat. don't know what the price tag is though.

[jblee10]

I've done switch barrel Mausers and Savages. I don't think it is worth the effort. I ended up looking for actions and stocks on both brands. The problem is change of accuracy and sight settings. Mausers are great. On a 94 or 96 Mauser I would build a nice 7x57 (or my personal favorite, 6.5x55). Stick with one caliber and shoot the heck out of it. By the way, I am still looking for one 94 or 96 Mauser action, one 98 action and a short action Savage.

[leadman]

I bought a 1909 Arg barreled action many years ago. barrel was a sewer pipe but the receiver sight on it was worth what I paid for the barreled action. Plans are to barrel it this week with a 6.5-06 barrel and put it in the McMillan stock I have.

[flounderman]

I have a small thread from a turk, 8mm, 28 inches, real good barrel, military sights, cheap. threads are the right size for the small rings, don't know if the headspace would be right. could be a screw in.

[HollowPoint]

I just recently re-barreled my old No.4 Mk1 Enfield using the Savage-Barrel-Nut method with the idea of using it as a "Switch Barrel" rifle. For all intents and purposes I think it turned out well but, after having done so, I'm now looking for another donor Enfield with which to build the 45-70 I intended to use as the barrel to be switched with this set up.

The "Switch Barrel" sounds like a good idea; and it actually is a good idea but, a more convenient idea is having two different rifles in the calibers you were wanting to switch back and forth to. This allows one to skip the "Switching" step and just go directly to the load and shoot step. (at least in my case)

Since it's your rifle, I say make it the way you want to make it. As long as the cartridge and the action is rated to withstand the pressures generated by your chosen chambering, you should be OK.

Best of luck with your project. I hope you'll post some pics when you're done.

HollowPoint

[MBTcustom]

I got the idea for part of this when talking to a guy that rebarreled benchrest guns. He said the barrels do not necessarily needed to be cranked way tight.

The thing about the tightness is, if you are using a righthand twist barrel, the boolits will tighten the barrel to the threads (the heavier the boolits the tighter the barrel). If you are using a lefthand twist barrel, you are going to need a lot of torque to prevent the barrel from being unscrewed by the boolits. Thats the real reason why most barrels are RHtwist. It has to do with the threads a lot more than the flight of the boolit. The British Enfield used a LH twist barrel to compensate for the action because it was stronger being twisted one way than the other. However, they still had RH threads on the barrel, so the British enfields are always trying to unscrew the barrel from the action. They dont do this of course, but thats because they torqued their barrels to 125 Ft/Lbs!
I also wanted to let you know that if you are going to do this, be sure to break in the threads real good before you call a certain spot good. I have found that my barrels screw in further and further as the threads crush properly. As a thread is torqued for the first time, there are only two threads that are actually touching. As the thread is worked, the bearing surface of the thread gets larger and larger creating a more positive stop. NASA actually tested this and created bolts with floating threads. The problem was that they would torque the bolts down on flight hardware, but after making it to space and back, the bolts would not be tight anymore. All the shaking and temperature cycling (much the same thing that a barrel goes through) would peen down the two contact points on the bolts and they would "loosen". The ideal solution would be to make the threads tight and lap them together so that they mate perfectly over all the threads. That idea is time consuming and full of its own troubles.
I would think that the best way to do this would be to get all the barrels you want for the project and thread them to exactly the same pitch diameter measured by wires. Screw the barrels one by one onto the action to a predetermined torque. Do it about ten times. Then chamber the barrels and set the headspace for each one. That would insure that they all act the same way and stop consistently at the same point every time, and If you use one a lot more than the others, it wont change the way the other barrels match up.
This is all just theory on my part based on information that I have gathered. I had a very similar idea in mind at one time, but I never followed through with it.
Its just something to think about, and I hope it helps.

[MBTcustom]

A slight modification to my previous post.
I have recently been made aware that it is not necessary to use any real amount of torque to install a barrel. Since a RH twist tightens the barrel onto the action, it is not necessary to do any more than bump it closed. So it may not be as necessary as I originally thought to break in the barrel threads. Sorry for the misinformation.

[leadman]

I may not do the switch barrel part until a later date. I have decided to buy a new stock and trigger for this gun and a new trigger for another Mauser I am assembling. I will still have the capability of adding barrels later.
I disassembled a Turkish 98 I put together many years ago after having a gunsmith put a barrel on it in 6.5-06. The barrel came loose while shooting it. I decided to investigate why the bolt is kinda wobbly when opened and found the top guide rail is much too wide. I had bent the bolt handle and shaped it so the number is gone and I don't remember if it matched the receiver.
I tried the bolt out 1909 Arg that I am rebarreling to 25-06 in the receiver and it is tighter but not like it should be. The bolt for the Turk is a different length than a standard 98 so I may have difficulty finding another.
I did find some 98 receiver complete on Gunbroker for a decent price so may buy one of these.
More fun.

[leadman]

My Mauser project is not going well with the Numrich barrel in 7.62X39. The first new barrel had an 1/8" wide ring that measured .308" one inch from the muzzle. the reat of the barrel measured .310" to almost .311". This barrel had light rusting in the center of the barrel. Called Numrich and sent it back and ordered a second barrel.

The second barrel had an identical ring in the barrel plus a large amount of rust in the center extending to about 3" to 4" from each end. I cleaned it out but without a bore scope I can't tell if it left pitting or not. I will call Numrich Monday.

[MBTcustom]

Hmmm. Thats a big NG (not good)
If you will pardon the question, Why are you trying to use the original wartime toiletry instead of new Adams and Bennett barrel blank stock? The barrel blanks are about the same cost I think and with the A&B, you get a brand new, good quality pipe that will give sub MOA more often than not.

[leadman]

The barrels from Numrich are brand new barrels, short chambered and the exact dimensions externally as the A&B F14.

I think I have the problem figured out. My son brought over the Mauser 98 in 308 Win I did for him along time ago. It has an A&B F14 countour barrel on it. I compared it to my barrel from Numrich and the only difference is his barrel is shorter by about 1 1/4", exactly the amount I need to cut this barrel off to remove the "ring"!! Both are listed as having a 21" barrel but his is just under 20".

I'm going to call Numrich in the morning and if they have no good update for me I will just cut this off and call it good.

Another reason to not use an A&B barrel is Midway does not offer one in 7.62X39 with a
.310" or .311" bore. The only other barrels with the proper bore I found were over $300 and not threaded or chambered.

[leadman]

Well, I now know why there are not many of the Mausers converted to 7.62X39. This does not feed well at all and when extracting the case it comes loose from the bolt face. I did buy Numrichs' feed kit but it is not designed correctly.
It actually feeds better with the original follower and spring but there is so much extra length in the magazine for the cartidges to slide around in they don't stay stacked properly.

It appears to correct the feeding I will need to weld up the feed ramp and the rails on the action above the magazine. The cartridge is coming up out of the magazine box too soon and points to the side too far due to the shoulder being so much smaller than the original 7X57 case.

I may buy another barrel in 7X57, or rechamber this one to 7.65 X 54 Arg. I'm set-up to cast and load for both.

This is getting to be a project that is dragging out too long.

Has anybody here tried welding the rail and the feed ramp?

[flounderman]

if you look part way up the bottom side of the rail you will see a shoulder was put there to steer the case away from the rail as it was pushed forward. if the case is coming out too soon, the shoulder is too wide, and that is why it doesn't feed straight. the case is too short. taking some off the shoulders would delay the case coming out. it might correct the problem but work slowly. what it needs is for the shoulder to be moved closer to the chamber but taking some off the shoulder might work. as for the case not staying in the extractor, is the rim thinner than a normal 7mm or 8mm. is it as wide? if it isn't as wide as the bolt was made for, it can't hold the case head against the other side of the bolt face and just falls out.

[leadman]

The 7.62X39 is smaller in the base but I made some progress there by trimming the inside of the extractor so it fits over more of the bolthead. If I can't trim enough I may weld on another piec and shape it to hold the 7.62X39 case.
I also was also remembering an article I read, think it was by Ackley on feeding from a Mauser magazine.

I took some of the metal duct tape with the sticky back and put 2 layers on each side of the receiver above the magazine and extended up the hole so it made the inside of the hole smaller. The cartridges fed perfectly from the magazine!!! Two layers of tape measured .008" thick.
I have to find some shim stock .008" thick to make pieces to either solder or expoxy in place. If I can't secure it adequately to the receiver I may extend the metal shim all the way to the bottom of the magazine. Will have to see how it works out.

[MBTcustom]

I took some of the metal duct tape with the sticky back and put 2 layers on each side of the receiver above the magazine and extended up the hole so it made the inside of the hole smaller. The cartridges fed perfectly from the magazine!!! Two layers of tape measured .008" thick.
I have to find some shim stock .008" thick to make pieces to either solder or expoxy in place. If I can't secure it adequately to the receiver I may extend the metal shim all the way to the bottom of the magazine. Will have to see how it works out.

See, thats exactly why I want a TIG welder! Those feed lips are like the edge of a knife and they are so critical to reliable feeding. That is the place I get stuck in the mud with every Mauser caliber conversion. If you got the welder, no problem! You can message the edges in or out and find out what the cartridge likes. As it is, I have a build going now that is going to sit right where it is until I get that welder. Of course, for me, I can justify it as a business expense some day, but even then, those mothers are expensive!
I like your idea with the shim stock. I tried that on my build, but I couldn't make it rigid enough to know for sure if it was working or not.
Have you given any thought to blocking up the magazine to make it hold the shells better?

[Nobade]

Score High benchrest followers make this kind of thing a lot easier. Of course it's then a single shot, but for the range it works great.

[B R Shooter]

I would like to comment on a couple things that have been discussed here.

"Switch barrel": It's done all the time, it's nothing new, and it's easy. If you have a Remington or similar that uses a sandwiched recoil lug, it takes a bit longer, but still easy. Chambering multiple barrels for one action should be no more difficult than chambering one barrel. Each action I work on, I record the serial number and I take measurements of the barrel when the first barrel is complete. I can then use those measurements and chamber barrels from then on and not need the action, which even includes the timing of the barrel pulling up in the same position each time. As long as the cartridge bolt face is the same, it will headspace and tighten the same. Plus, switching from one barrel to another, within reason of cartridge, the impact will be within a couple inches. One or two shots and you're good to go.

"Torque": A barrel needs to be torqued fairly well. I don't think anyone relies on the twist of the barrel to tighten the barrel. Look at what you have. You have a barrel that is over 20" long being held by and cantilevered by about 1 inch of threads. That's a lot of overhang. The barrel must be tight against it's shoulder in order to dampen the vibrations and hold point of aim. With any decent barrel vise and action wrench, you should easily be able to get at least 80 foot pounds of torque, 100 is better. Lube the threads, and lube the shoulder mating surfaces.

[MBTcustom]

"Torque": A barrel needs to be torqued fairly well.

There are some gunsmiths that would disagree with you on that point. I understand about cantilevering and all that stuff, but excessive force is excessive force. Sometimes, just because it seems like a good idea to scronk the living schite out of it white knuckle tight to a silverback gorilla, doesn't mean that you should.
I'm still figuring out where I stand on this point. However, I dont whack my molds with a piece of timber anymore, and I always thought that was necessary. I think there are a lot of things in this sport where we are a little nervous, so we substitute brawn for the brains we lack. (That comment was not directed at B R Shooter or anyone else, just a figure of speech!) Just saying that sometimes less is more.