I am considering taking one of my actions and working out a switchbarrel project.

My idea: Rigby bolt face Montana PH action. Two barrels, one in .450 rigby (#5 contour, 23" long), one in .338 Lapua (#4 contour fluted, 26" long). Maple stock.

Thread the barrels to seat on the inner C-ring of the action to set and maintain headspace. Make a barrel nut to lock it down ala Savage. Problem one is to figure out how to make a barrel nut look good.

Make the fore end detachable so the barrels can have open sights. Attach the fore end to the main stock with a hook and lever system. I would like it to be tool less or nearly so. Just a spanner for the barrel nut.

What issues am I missing here?

For the .450 it will probably weigh the right amount at about 10 lbs. I would like the .338 incarnation to weigh no more than 9 lbs. The PH action is heavy, so that might be a trick.

How much weight can be taken out of one of these actions? I can see several places where I can make lightening cuts. There is a lot of extra metal in the rails and recoil lug area.

And, yes, I know it is a lot of work, but I am doing it myself. This keeps me out of the bars.

Alright, let me have it.

Jeremy

It will work fine. You can remove most all the metal you want out of the receiver, rearward of the locking recesses. Lock nut can be any shape you want; I might knurl it. I assume this is not open sights only, but the original "Screw in the receiver side" TD system works too, just not as rigid as the barrel nut.

If you're going to be doing custom work, then I'd suggest skipping the nut. The advantage of the nut is you can set headspace without a machine shop. Just make each barrel fit the receiver, and if you're going to be swapping them a lot, maybe put some flats on them or some other arrangement that makes it easy to get a wrench on it. Without the nut, you just screw the barrel in and torque it to the same value and no messing with nuts or headspace. I'd also suggest using optics with turrets you can trust when switching back and forth.

I've been doing switch barrel stuff for a while now and have had good results. It amazes me how I can take the whole gun apart, put it all back together later on and the zero is the same for that configuration.

Yes, that works fine but the OP wants something he can do in the field without tools. I think.

Thanks guys.

I think that the nut will lock it down better and maintain accuracy better. That is totally a theory, though. I don't have real world experience with take down systems. Someone uses a lock nut system, but I can't find the web page that I saw it on. Their system had a fixed forearm, so no open sights. And I don't know how they maintained headspace.

Headspace on the MRC actions is easy since they have an inner C-ring to butt the barrel against. Once it seats, headspace should be reliably set. It should also be tolerant of thread wear over time. One concern is the sights canting with thread wear. That is probably just going to happen.

The nut was also my way to lock it down and keep a free floating forearm for bipod use.

No tools, is one of my goals for this since tools get lost, damaged, and could require a trip back to camp. That brings up the issue of keeping the lock nut tight. If you don't torque it a little, it will want to loosen up. Maybe an o-ring like the Lee dies use on their lock nut? I suppose a tool could be part of the forearm, or contained in the forearm.

None of this is set in stone. These are just my thoughts on how to do it, and I am open to changes.

Jeremy

You can make a nut with original treading to the action and a finer thread to the barrel so you only use handforce to switch(it just looks like a pice of the original barrel).

I hadn't thought of that. The barrel thread is 16tpi. Maybe go to 24 tpi and use a 2" long nut so you have a good grip on it. Each barrel could have a dedicated nut that conforms to the barrel contour.

As DPCD suggested, knurl it as well. Fine flattop knurling wouldn't be too bold.

Jeremy

Not sure about the O ring idea; but I don't think it will hold zero; now if these are iron sights only barrels, then hell, you don't need the barrels to be tight at all.
The original Mausers use a setscrew that is slotted for a coin. Some are bigger and knurled.
I do not like the threaded sleeve thing; sorry Nord. I don't see any benefit and I do see more work.
If you want a good grip on the barrel, just leave a 2 inch knurled section on it and don't use a nut at all.
What about a little spanner wrench for the nut? I know, you want no tools....just thinking out loud.

A spanner is probably the best solution to tightening up the nut properly.

It could be housed in the forearm, or even be part of the forearm assembly. I'll have to draw that out on some scratch paper and see.

Now that I re-read Nodic's response I see that I mis-interpreted it. I was thinking about threading the nut finer to increase the axial force when it is snugged up. I didn't think about a separate sleeve.

The .450 barrel will have open sights and a low power scope to go with it. I did find an old post from Duane Wiebe on his system. He used set screws on banded front and rear sights so they could be re-aligned as the threads wear. That is probably the best solution to that issue.

The .338 barrel will not have open sights, and would be a scope only setup.

I am still thinking a nut is going to be the most accurate configuration with the least amount of machining.

Jeremy

A spanner could be housed in the butt under a trap door. Eliminating barrel mounted rear sight and using a peep on rear scope base will eliminate need for special forend. These are things I'm considering for a combo 7mag/375h&h. I'm also looking into octagon to round and using padded wrench on the flats. Front sight would be a sleeve that could be rotated and held with screws or muzzle nut. Changing in the field isn't a priority but it could be done.

Gzig, were you thinking of octagon for a large portion or just the last inch or so at the breech?

A rear peep is a good idea. It would be slick if it were integral to the rear bridge or scope base rather than be detachable. I will lose a detachable one. Then find it again too late to help and in a place is shouldn't be.

I would like a fat squishy recoil pad. I have not seen that as a trapdoor setup. Though a cartridge trap could work similarly. A spanner wouldn't need to be larger than a cartridge.

Thanks folks.

Jeremy

Octagon just past end of stock, maybe with a wedding ring treatment around wrench area. Squishy pad complicates hiding a wrench or peep but I can envision a hinged butt pad that would swing out to completely expose the butt. Flip up peeps can be integrate into the scope base.

I have 3 switch barrel rifles, none have a nut, 2 are Win Model 70's CRF's, one standard length and the other magnum length. The other is a Rem 700 S/S short action. Soon to have another Rem 700 long action completed, too.
I have successfully used all 3 by simply hand tightening the barrels by holding the stocked action between my legs, even after a range session of around 30 rounds, the barrels did not loosen. The barrel shoulder is what holds the barrel in place, not the threads. If you use a piece of grippy leather or chamois material, you should be able to tighten the barrel firm enough for it to stay in place, if not, use a barrel vice and action wrench, which only requires a slight amount of torque to nip up the barrel anyway. If everything is true and square on the barrel shoulder, the amount of friction when tightening the barrel is substantial, a lot more than most people realise.

Cheers.

Do you see repeatable accuracy? Meaning can you sight in, pull the barrel, put it back on and get a reasonably similar group on the target?

I agree that you can get a tight barrel with very little force. I've had to put hand tight barrels in a vise to get them back apart.

I assume that you have no open sights, and use a standard stock?

Thanks for the info.

Jeremy

Thanks, Duane.

I have read a few posts on here about your take down designs and appreciate the feedback.

Over the life of a simple take down, one where the barrel threads on and has a simple catch to lock the forearm, how accurate do they stay?

I would like the rifle to be accurate enough to 500 yards for hunting. So say a 6" group at 500 yards, an inch or a little bigger at 100 yards.

That is where I was thinking a nut or other locking system would be beneficial.

Jeremy