Sleeve a Barrek Shank

Recce21

Recce21

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Is it possible to sleeve a smaller diameter barrel shank to fit a larger diameter receiver? I have a M21x1.5mm barrel shank and the receiver is a M26x1.5mm thread. Are there any other possible ways to use the smaller diameter barrel? Will there be any strength/pressure issues?
 
With a 5mm difference the best way would be to make a threaded sleeve to fit the barrel. I'd go for a light interference fit so the sleeve has a firm but workable drag as it threads on. I'd clean and "glue" it onto the barrel with some stud and bearing mount thread locker. Then turn the barrel and sleeve together for the outside thread to fit into the receiver. Done this way the barrel would effectively now be the bigger thread since it would be tough to remove the sleeve.

The barrel is designed to hold the pressure of the round without the use of a receiver. So adding a sleeve adapter like this isn't an issue.
 
Thanks for the info! I really appreciate it.
This is for a one off project where if done right, will be pretty bad ass.
Mum on details right now until it is done. Don't want to get mine or anyone else's hopes up.
BCRider said:
With a 5mm difference the best way would be to make a threaded sleeve to fit the barrel. I'd go for a light interference fit so the sleeve has a firm but workable drag as it threads on. I'd clean and "glue" it onto the barrel with some stud and bearing mount thread locker. Then turn the barrel and sleeve together for the outside thread to fit into the receiver. Done this way the barrel would effectively now be the bigger thread since it would be tough to remove the sleeve.

The barrel is designed to hold the pressure of the round without the use of a receiver. So adding a sleeve adapter like this isn't an issue.
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I've been giving this some thought and while I agree with BC on the burst strength of the barrel steel holding at the tread buttress, I would be very concerned about the strength and integrity of the steel collar he talks about after the outside tread has been cut. The amount of steel left between the internal and external treads both cut in the collar would not be very thick and I would be concerned that the barrel may eventually just "uncork" ( for lack of a better term) from the action at combustion pressures. Sort of " the bolt pressure holding at the lugs, and it pushes the barrel away from the bolt face", creating headspace in reverse to what we usually see.
 
fingers284 said:
I've been giving this some thought and while I agree with BC on the burst strength of the barrel steel holding at the tread buttress, I would be very concerned about the strength and integrity of the steel collar he talks about after the outside tread has been cut. The amount of steel left between the internal and external treads both cut in the collar would not be very thick and I would be concerned that the barrel may eventually just "uncork" ( for lack of a better term) from the action at combustion pressures. Sort of " the bolt pressure holding at the lugs, and it pushes the barrel away from the bolt face", creating headspace in reverse to what we usually see.
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I understand what you are saying but it does not work like that. Regardless of the thickness of the collar, the entire length of threads would have to deform and shear in order for the barrel to "uncork". If you made your collar out of lead, then this may be remotely possible, but just about any other material, especially steel, willd hold for many lifetimes of SAAMI spec ammunition.
 
there is not much strenght required
most old over and under ,side by side shotguns and variations combi,....double rifle express are just sleeved in and soft soldered in ... beretta always soldered all of it
yep nothing more or less with the same tecnique a plummer welds copper pipes..........
after many years other factories (bernardelli )started soldering with Castolin silver solder...with different brass-silver %
only because of ease ofmanufacturing
a good treaded sleeve and red loctite would be enough
 
Love the info guys.
TO come clean, I am rebarreling a Valmet Hunter with a 18.1" Galil barrel. Galil threads are M21x1.5mm and the Valmet receiver is M26x1.5mm
 
Fingers, keep in mind too that the internal threads of the sleeve extend inwards even more than the barrel stub's 21mm major diameter. It's only on the outer 26mm thread that the sleeve is being "thinned" by the thread depth. And with the fine thread of 1.5mm pitch you'll still have between 2.5 and 3mm of unmolested wall thickness between the two extreme thread valleys. That's more than enough to ensure that the metal can't strip itself out between the thread valleys.
 
It actually doesn't! I thought it would too but it wasn't measured like the RCMP tell us to here. It is marketed as 18.1" but when I measured it from bolt face to end of rifling, it came to just 18.5".
 
Blast & BC, I appreciate your opinions as well but am still suspect of the outcome of this project. BC with internal & external thread coming at each other, the thread crowns still point at each other and in this case not very far apart. After cutting both threads in the collar, really what you are left with in the end is similar to a thin winding of steel wire with a thin 2.5 mm web joint between each strand holding back 50,000 lbs.. The thread cutting action/tool pressure from both sides will for sure already start the separation process at this weak spot. It doesn't have to "shear" as Blast suggests, just come unwound at the web. And remember, pressure damage is cumulative, if it holds for the first ten or eleven rnds, will it hold for the twelfth.
It probably would hold at the 18-20,000 lb pressures that are expected in the shotgun or old Express black powder cartridges that Ago talks about but if Recc plans on shooting something with 40, 50 or even higher pressures I would be worried.

Just a humorous addition, I have seen a shotgun barrel come unhooked from the gun at the silver solder spot. When I was a kid, tagging along with my dad on a duck shoot, he pulled the trigger on his old Browning Auto five (very old, 4 ser # gun). The barrel left the blind and was javelined into the barley swath about 40feet in front of us. The silver solder between the barrel & the slide ring had let loose... took it to the shop, brazed it back together with a "really big gob of brass so it will hold better" and back to the duck blind for the rest of the day. I still have that shotgun and altho I have never shot it, the brass held as long as the old man used it
 
fingers284 said:
Blast & BC, I appreciate your opinions as well but am still suspect of the outcome of this project. BC with internal & external thread coming at each other, the thread crowns still point at each other and in this case not very far apart. After cutting both threads in the collar, really what you are left with in the end is similar to a thin winding of steel wire with a thin 2.5 mm web joint between each strand holding back 50,000 lbs.. The thread cutting action/tool pressure from both sides will for sure already start the separation process at this weak spot. It doesn't have to "shear" as Blast suggests, just come unwound at the web. And remember, pressure damage is cumulative, if it holds for the first ten or eleven rnds, will it hold for the twelfth.

It probably would hold at the 18-20,000 lb pressures that are expected in the shotgun or old Express black powder cartridges that Ago talks about but if Recc plans on shooting something with 40, 50 or even higher pressures I would be worried.
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Ok, but you still do not understand that this is irrelevant. The thickness of the adapter does not matter, as long as the total thickness of the barrel, adapter and receiver are enough to exceed the burst strength requirements, and the threading on the adapter has enough shear strength to exceed the thrust being placed on the threads. Nothing else matters. If both threads were the same pitch, he could quite readily employ a Helicoil, which is simply a thread shaped wire that allows you to either repair/replace damaged threads, or reinforce threads in soft materials. Also keep in mind that because both parts have a different thread pitch and both parts will be held in tension, it is virtually impossible for the adapter to "unwind" as both sets of threads are cross-compressing it.
 
I had a very good bbl maker and gunsmith sleeve a 308 target rifle with a Mauser 98 action when the previous owner had taken a grinder and crudely ground down the chamber end of the bbl (for some reason ) until the chamber was too short.

The smith made a threaded sleeve to insert into the action, and threaded the bbl (if I recall correctly from 30 years ago) and screwed it into the sleeve, re-chambered and it shoots little bug holes.

When he took the rifle apart to see why it was not chambering well, I recall my heart sinking, but I recall him saying " ...here's your problem... but there is more than one way to skin this cat...." It was a great repair for good value as well.
 
Thanks everybody continuing to throw their 2 cents in. This project if it works (finders crossed) is going to be awesome. I also have a SAR parts kit with 13" barrel that if this goes well, I will be doing the same. That one will obviously be restricted though.
 
Swiss K-31's have been done this way using a barrel stub/sleeve to chamber .308 Win. Haven't heard of any of them coming apart.
AR-15's contain a .980" chambered barrel with a steel sleeve around the tenon inside an aluminum receiver.
I can't see an original barrel chambered for .223 for the OP swelling or blowing up just because a sleeve is added between the new receiver.
 
If you feel the threads are too close, the barrel can be turned smaller and threaded with a finer thread and then a bushing added to it and threaded to fit the action.

I threaded a 700 action larger and made a bushing to fit the action holding a Holland lug indexed in place. The internal was threaded for a 1 inch thread 1 inch long. It is kind of a switch barrel action now and I can fit just about any take off barrel to it... The bushing was Red Loctited and torqued to the action.

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guntech said:
If you feel the threads are too close, the barrel can be turned smaller and threaded with a finer thread and then a bushing added to it and threaded to fit the action.

I threaded a 700 action larger and made a bushing to fit the action holding a Holland lug indexed in place. The internal was threaded for a 1 inch thread 1 inch long. It is kind of a switch barrel action now and I can fit just about any take off barrel to it... The bushing was Red Loctited and torqued to the action.

bushing-0.jpg

bushinginstalled-0.jpg

bushinginthestock-0.jpg
Click to expand...

Neato. What did you use to torque in the sleeve?
 
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