"No barrel nut no shoulder" idea

Just thinking out of the box here... ::)

This is strictly hypothetical: Haven't done it, and don't have the desire to try it.

I'd like to float this test balloon for academic discussion only: the idea would be to drill and tap a hole in a savage action such that a brass-tipped setscrew could be used to to lock in the barrel after screwing it in to the correct headspace. The setscrew would be tightened against the barrel threads inside the receiver to keep the barrel from moving or turning.

Possible Pros: Eliminate the need for barrel nut or shoulder. Lighter weight for those for whom this is important. No barrel nut wrench needed.

Possible cons:
Not sure the barrel would be "locked in" as well as with the barrel nut or shoulder which both apply an even axial tension to the thread faces to keep the barrel from wiggling due to the inherent "slop" or runout in the mating threads. Might need a couple of setscrews?
Not sure there is an appropriate place or places on the receiver to drill the hole or holes without weakening.

Also, this type of attachment puts a slightly different stress on the receiver. Eliminating the compressive force of the barrel nut/shoulder against the face of the receiver, (I think ) would possibly increase the bending force on the receiver in the area of the threads. (Don't know if this would be a adverse factor or strictly an academic note.)

Anyway...once again, I got to thinking and thought I'd mention this as a discussion topic.

Just wondered if anyone else had thought of this and if so, what are your ideas.


By the way, I realize that I am not smart enough to have been the first guy to think of this...and it has never been done, to my knowledge, which makes me think that the cons must outweigh the pros.
Cheers

Many switch barrel rifles use a screw to keep the barrel from turning out of the action but these barrels also have a shoulder to put the threads in at least some tension. Most of these type setscrews are threaded tangentially to the receiver ring in such a way that they bear on a milled portion of the barrel tenon pushing the barrel in the "tighten" direction.
You could lock a nutless and non-shouldered barrel to a receiver by milling a slot through the receiver ring and then welding two opposing lugs spanning this slot through which one or two socket head capscrews would serve to compress the slot and lock the barrel in with the threads in interference.

Where would you put the recoil lug? Only two options I can think of would be welded to the receiver ring or a slot milled some where in the ring to mate to a lug glued into the stock.

Quote:

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Originally Posted by BobT

Where would you put the recoil lug? Only two options I can think of would be welded to the receiver ring or a slot milled some where in the ring to mate to a lug glued into the stock.

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Like an Axis? ;)

Even on an Axis he recoil lug is sandwiched between the barrel nut and the slot. In fact during recoil since the barreled action wants to move reward the force of the recoil is brought to bear against the barrel nut.

Given that head space is pretty critical and a relatively few thousandths of "extra" can quickly lead to case separation and shooter injury, I think that the problem with this type of concept is that by trying to locate something with setscrews as opposed to either a nut or barrel shoulder, it will be prone to "wear" rapidly and become slack quite fast. If it was for something like a bang stick for use on sharks when diving, it would be a different consideration that a rifle, which one expects to fire thousands of rounds with consistency.

I suspect that such a rifles ability to group would rapidly deteriorate, ending in case separation. I for one would not like to be the shooter next to you on the range. There were many examples of attachments to the end of hydraulic cylinders fatiguing due to the nut not being secure and the slop in the threads leading to high local stress concentrations, which got a crack started which finally resulted in the detachment of the load from the cylinder rod. In some cases they were fatal incidents, which was why they were investigated by proper failure mechanics inspectors and added to the list of "case studies" in the handbook.

This is one situation where I think that the manufacturers are right in recommending not modifying your weapon. If you are not capable of designing it from scratch, it is probably not safe doing this kind of experiment. If you want a better "quick detach" system, look for something that is cam locked, like the machine gun barrels (although they are hardly masters of accuracy) or just use a barrel shoulder and put wrench flats on a suitable accessible position like near the muzzle. The barrel does not have to be torqued on to 100ftlbs, what it needs is to be consistent and 25-35ftlb is probably enough.

Personally, a solution to a none problem. Trading the barrel nut (easy, fast, and reliable) for a set screw does not thrill me. I think the Savage barrel headspace system is tried, proven, and easy. Need reference marks, scribe them at lockup.

Larry
Tinkerer

Good replies. Thanks for your thoughts.
I figured there were reasons I hadn't initially thought of that would make it not such a good idea.
As I stated in original post:

Quote:

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Originally Posted by thomae

This is strictly hypothetical: Haven't done it, and don't have the desire to try it.
...it has never been done, to my knowledge, which makes me think that the cons must outweigh the pros.

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Again, was not trying to solve a problem that does not exist, or reinvent a wheel that is still runs true. It was simply a discussion topic for some of the smarter-then-me people on this forum.

How about another approach. Make an Aluminum nut without any wrench access. Add set screws to this nut. Then what you have here is a light weight adjustable shoulder that fixes itself to the barrel and any thread damage to the threads it not in the range of the actions threads.

you still have the adjust ability for headspace control. Light weight. And easy off easy on of the shouldered barrels.

just another hair brained idea.

http://switchbarrel.blogspot.com/
http://4.bp.blogspot.com/-8thzu5-FU1...Muzzle+Hex.jpg

http://4.bp.blogspot.com/-YPyCXiVG1A...rrel+Shank.jpg

Hmm - if only someone would come up with an interrupted thread barrel shank and some kind of key/slot mechanism to lock the barrel in place, it would only take the push of a button and 1/4 twist to remove a barrel...

http://i220.photobucket.com/albums/d...rdite/3031.jpg

http://i220.photobucket.com/albums/d...rdite/3032.jpg

http://i220.photobucket.com/albums/d...rdite/3033.jpg

http://i220.photobucket.com/albums/d...rdite/3034.jpg

Although I must admit I like Winchester's method better because it let you tighten things up once things got worn.

A shoulder cut on a barrel will definitely get rid of the need for a barrel nut. However as has been mentioned above. The high pressures we deal with and a fraction of an inch making such a huge difference...is it really worth it? Sure a scribe line can be made on barrel and frame to ensure things are lined up. But to ensure that the barrel doesnt move at all....is the nut such a big deal?

I do not like to be a naysayer to anyones innovations, but how much does a barrel nut weigh? I say if you have have to eliminate the barrel nut, it causes a LOT more work, cause the barrels will more than likely have to be hand reamed to set headspace, because some sort of pressure point will be necessary to insure headspace stays where it was set.

Seems one could lose more weight by going to a thinner barrel, or heavier barrel and fluting.

Lots of good thinking here. Thanks for all your comments.
(Buncha good people on this forum!)