Savage switch barrel

[Buck Fever]

Some people do a switch barrel with the barrel only torqued to 30-40 ft-lbs. That seems silly to me because if the barrel loosens or tightens at all, the zero will change.

To me, the thing a switch barrel rifle needs is tool less assembly and disassembly. If you need a barrel vise and action wrench, what have you gained?

Similarly, when you go to an action with a well defined barrel tennon like an ARC action, a shouldered pre-fit makes a lot of sense (that's what I did with my Archimedes) unless you specifically want to make it a switch barrel setup or you want a Barloc just to make a full DIY gun assembly without a barrel vise or action wrench (that's what I did with my Nucleus and a Proof CF barrel).

Then I read about setscrews and now I'm really confused. What are you hoping to accomplish? Is it just turning a Savage pre-fit in to a shouldered barrel? If so, a better method would be to find someone to make thin barrel nuts so you can double nut and secure your shoulder that way. Even if that is exactly what you want, I still wonder why? Just get a GO gauge and a piece of tape, it's really not that hard to set headspace with a barrel nut.

 

[1mechanic]

I want to set the headspace and lock the barrel nut in place to be able to use an internal action wrench and tighten to 30 or 40 ft-lbs without removing the scope. 30 to 40 ft-lbs is plenty to hold a barrel in place. I don't want a shouldered barrel. I want to be able to remove the nut and rechamber the barrel and set the headspace again with the nut and set screw.

After reading post #2 from can1010 I think three equal spaced set screws would be better.

 

[Buck Fever]

I still don't get it, a double nutted barrel nut would be better, with no risk to the threads or loctite required...

 

[ntsqd]

The one switch barrel rifle that I've ever seen switched at the range used a strap wrench as the only tool. No action wrench was used. Torque spec was one grunt. They were shouldered barrels in a 700. This was about 1985 or so.

Jamming the barrel nut either with a thin nut or with the set-screws means that the head space for that barrel is set. Can think of it as a user adjustable shoulder.

Once the head space is set I wouldn't use a tool on the nut to swap barrels, only a strap wrench on the barrel itself.
I'd only use either the brass tipped set screws that I linked earlier in this thread or the nylon version of the same thing. I'm not going to use 271 on scope ring screws, but at the same time I don't fear Lock-tite either. A drop or two of 241 in the barrel threads wouldn't be a bad thing.

The thin nut jamming the barrel nut is arguably the more elegant solution, but either method will work. Could make a thin nut by simply facing off and narrowing a barrel nut. Parallelism of the two sides of such a nut would be of the highest importance and I'd start with a high quality nut so that the first face is assumed to be very perpendicular to the threads.

 

[Buck Fever]

You could use a barrel nut wrench on a double nutted barrel, just tighten on the muzzle end of the double nut and loosen on the chamber end of the double nut.

Using two barrel nut wrenches to tighten the double nut against itself would be a good idea too.

But a custom double nut, two barrel nut wrenches and an action wrench, I would rather just buy a Barloc which is what I did...

 

[ntsqd]

While those techniques will work, using the nuts to R&R the barrel always poses the risk of changing the head-space unintentionally. Better to not touch the nut or nuts once they are set.

With the typically lower barrel install torque of a switch barrel system all that you need is a strap wrench on the barrel. Although I don't have a switch barrel rifle, this is the strap wrench that I have for other needs: https://www.toolsid.com/otc/16-strap-wrench-mpn-7206.html

I've yet to find a illustration or a good description of how exactly the Barloc works. I have seen pictures of some of the separate parts and those give me what may be a decent guess, but it's still just a guess.

 

[Buck Fever]

Look up a jack screw, that's exactly what it does, in miniature.

The middle part is a clamp, the front is a barrel nut with a toroidal section and the recoil lug also has a toroidal section. With the clamp loose (or slightly stretched as I do it), the barrel nut can be tightened with a tiny wrench or by hand to lock the headspace in, then when the capscrew in the clamp is tightened it acts on the two toroidal sections, pushing them apart, tensioning the barrel threads. The clamp does not contact the barrel at all.

In a Video Ted made, he showed that the clamping that can be done by hand with an Allen key is equivalent to more than 150 ft-lbs barrel torque on a shouldered barrel.

A typical capscrew is a huge "nut" with a ring of smaller bolts around it, parallel to the main thread. When you have a large thread, the torque to properly tighten it is so high that tightening with a wrench becomes impractical so a jackscrew is used where the smaller bolts press down on a washer under the nut to tension the threads. At full scale this creates equivalent torques that are probably in the 10s of thousands of ft-lbs and more.

Instead of relying on 30-40 ft-lbs of torque keeping your barrel tight or hoping that your headspace doesn't change, Barloc secures a barrel just as well as most fully tightened shouldered barrels, you just have to have a GO gauge with you to swap and it will take a few minutes more than doing it with a strap wrench (but I don't know why you would be in such a hurry).

 

[ntsqd]

Some of the access plates on valves used in steam turbine power generation use jack screws. My guess as to how the Barloc worked was wrong.

If removing a barrel with a Barloc means losing the head-space setting then it's great for a long term install, but nearly useless for a switch barrel. At least to me it is. To me the hole point of a switch barrel is that the head-space has already been set and I can swap barrels back and forth at will with no need to set it every time I install a new barrel.

The lone barrel switch that I've ever witnessed at a range was done between shooting relays in a BR comp. It needed to be fast, but that isn't to say that all switches need to be.

Someone at ARC seems to be fascinated by toroidial surfaces.

 

[Buck Fever]

The fascination with toroids is that a ring of contact is made even when there is some angular misalignment between the pieces.

I'm not at all concerned with adding a few minutes to the barrel swap and headspace time. It's not a machinegun but it's still probably fast enough to swap in a match.