Idea for a tensioned-barrel rifle

[Paul47]

Hello, first post here. I wondered what some of the gunsmiths think about this project.

Imagine first taking a standard Savage gun. Remove the barrel from the action and thread the muzzle. Throw away the recoil lug. Find an aluminum tube with the same OD as the action, and fabricate a large front washer with the same OD and buy a nut that fits the front threads. Now assemble the barreled action with the sleeve in place, the nut up front holding things together via the large washer. Hog out the forearm of the stock. Assemble the barreled action to the stock while gluing the sleeve to the stock.

In theory at least, the sleeve now becomes a part of the stock, and all recoil is taken up through it. The action need not be bedded at all, and bedding the sleeve is very easy to do. Despite being a glue-in of sorts, the action and barrel can still be removed from the stock.

Why bother? I assume a very light but long barrel can be used, thus giving good barrel rigidity to a gun that is reasonably light and not so front-heavy. Also, adding any accessories up front such as a scout scope mount or front iron sight is very easy since there are no longer any concerns about drilling into the bore. Picatinny rails that fit the Savage action will fit the sleeve too. An old-fashioned walnut stock may even work well with this setup, not affecting the accuracy with varying humidity.

Some concerns: I have read somewhere that aluminum is not very rigid, but surely it must be more rigid than no sleeve at all. Using a sleeve of such large diameter might make for a funny-looking gun, especially one with a narrow forearm. And I worry about the different expansion; as the barrel heats up, does the front barrel nut get loose? Does a barrel nut have to be right in front of the action to retain proper tension?

Any comments will be appreciated.

 

[tinkerer]

I, too, have pondered this.

My concerns:

1. Heating. The barrel will get hot and expand, the sleeve will not and AL expands at a different rate. You want to keep the barrel at the same tension, always.

2. Concentricity. The rear nut and the front nut must be absolutely parallel and the sleeve must be square on both ends or you'll induce some force one way or the other, so it would require radial nuts and a cup type fitting in the end of the sleeves to align perfectly. Could be done, but I refer you to 1 above again.

3. Recoil. The recouil will be carried by the rear nut/washer into the sleeve. Mass and vibrations will be induced.

I understand several barrel makers have investigated and used carbon wrapping on a flanged barrel arrangement to put the barrel under tension and the carbon fiber has been very good at heat transmission and dissipation.

So, can it be done, probably. Will it work, don't know, maybe. Will these be problems, possibly.

Am I helpful, doubtful. Try and let us know how it went.

Larry
Tinkerer

 

[gme]

You mean something like this;
http://www.teludynetech.com/home-hunting/
I have no experience with the system and don't know of anyone who's using it
Gary Eliseo

 

[aJR]

Hi All , I have been shooting a Tensioned Barrel set up for nearly 10 years .. As long as the tube has a total length even wall thickness it will work perfectly .. The real beauty of this system is it allows you to pick the speed of the bullet because of the reduced barrel vibrations .. Anyhoo here's a 1000yd target pic i shot recently in a registered match at my home range in Australia ,ten shots in Heavy Gun and yes it works great..JR..Jeff Rogers

 

[Paul47]

Yeah, I've heard about StraightJacket. I find their site a bit annoying since they hide the details of their technology, so you can't really figure out what is going on with it. But the one or two forum members (on another forum) I've seen writing about it seem satisfied.

1. Heating. The barrel will get hot and expand, the sleeve will not and AL expands at a different rate. You want to keep the barrel at the same tension, always.

Agreed, that is my concern. But whenever I find myself worrying about this, I then think about the current standard setup of floated barrels, and how silly it seems we are to expect them to vibrate the same way no matter what the conditions, and how we put up with the shortcomings by just adding steel, making the rifle ridiculously heavy. Maybe it wouldn't hurt to give a tensioned barrel setup a try.

2. Concentricity. The rear nut and the front nut must be absolutely parallel and the sleeve must be square on both ends or you'll induce some force one way or the other, so it would require radial nuts and a cup type fitting in the end of the sleeves to align perfectly.

I didn't explain myself correctly. There is no rear nut in my setup, any more than there is a rear nut in a Dan Wesson revolver. All locking pressure comes from the front nut, through the sleeve, applied to the front face of the action. Although, if that does not work, there is a fallback position to try that has both a front and a rear nut (probably as you imagined), with the rear of the sleeve bearing not on the action nor on the rear nut, but on a step near the rear of the barrel. That might also work better for actions that, unlike the Savage, have a barrel shoulder rather than a nut. I agree alignment must have some thought put into it. Parallel faces is not too tough; Mic McPherson has shown how to lap a Savage nut, recoil lug and action front face parallel. The ID of the sleeve can be just barely large enough to fit over the rear of the barrel, thus centering it back there. Up front the washer under the nut will need a shoulder that just fits inside the ID of the sleeve.

3. Recoil. The recouil will be carried by the rear nut/washer into the sleeve. Mass and vibrations will be induced.

Unless I am misunderstanding you, I don't see much problem with recoil, provided the sleeve is glued well enough into the stock. I suppose people paranoid about their .458 Mag barreled action flying back into their face, could retain the recoil lug also!

aJR, do you have any pictures or description of how your setup works?

BTW I've found another fellow who has done a tensioned barrel project here:
http://public.fotki.com/Rbertalotto/things-that-go-bang/tension_barrel_project/
I am trying to contact him.

I have tried to interest various gunsmiths in this over the years with little luck. I suppose they were all too busy with their regular work.

 

[aJR]

Hi 47, 3 pics.. Of breech end in which the adapter butts against the action face (1) ,the muzzle end of the tube and where it is threaded (2), The assembled barrel with threaded captive nut installed(3) .. Both ends threaded 1.250x 16 TPI ..Because the package holds no fluid to cool it it has to have a fair bit of tension so the barrel does not lengthen too much and come loose ,otherwise the degree of tension does not matter to either shot placement or grouping ..JR..Jeff Rogers

 

[aJR]

Pic of the whole outfit..JR

 

[Paul47]

Wow, that is a big gun! I was thinking more of something that could be carried around while hunting. The object would not be tiny 1000 yard groups, but reduced weight and improved accuracy, although the point you mentioned (not having to tune velocity to find accuracy nodes) is a definite plus.

Nice work, though. That's an aluminum sleeve, right? Apparently the barrel does not heat up enough to make the tension come down enough to ruin the group. Is the sleeve mounted or glued to the forearm? Guess it would have to be. I notice you went with a conventional shoulder on the barrel, rather than having the sleeve bear on the action.

 

[aJR]

Hi 47, We have conducted tests in 3 different formats ,, 1/ the one you see in the pic ,, Metric equal in tube to 2.0 in od with a .200 wall and no fluid cooling .. 2/ 1.500 od and a .125 wall on a light gun and no fluid .. 3/ 1.250 od with a .080 wall with no fluid .. 1st has a 1.500 barrel for 6ins tapered to 1.250 at 32ins in Heavy Gun .. 2nd has a 1.250+ barrel for 4 ins tapered to .900 at 32ins for the 17lbs class .. 3rd has light palma barrel at 1.240?? for 3ins usual taper at 28 to 30 in for anything lighter.. All have to have very tight tolerance in the wall thickness for the whole length of the tension tube to be successful .. I have sent Good tubing that i have found to friends in the US because they have trouble getting a good quality product over your way for what ever reason .. All have a different method of set up.. Barrels on my guns will always have a conventional method of attachment , ie action bedded only as i believe that there is still a small form of barrel compensation offered in this way that allows a tune to have a wider band ..JR..Jeff Rogers

Wow, that is a big gun! I was thinking more of something that could be carried around while hunting. The object would not be tiny 1000 yard groups, but reduced weight and improved accuracy, although the point you mentioned (not having to tune velocity to find accuracy nodes) is a definite plus.

Nice work, though. That's an aluminum sleeve, right? Apparently the barrel does not heat up enough to make the tension come down enough to ruin the group. Is the sleeve mounted or glued to the forearm? Guess it would have to be. I notice you went with a conventional shoulder on the barrel, rather than having the sleeve bear on the action.