Sleeving a barrel tenon

BK6BR · Nov 30, 2018

I've been thinking of this for some time now, years. I'm not a gunsmith but have always wondered why this is not common in the re-barreling of rifles. For example, instead of cutting a tenon and threading why not just sleeve and shrink fit? I've added a 3D model for further explanation. I'm sure there would be a massive amount of torque in the barrel while accelerating a mass down the riffling but surely it's not more than friction fit can handle. Maybe, the fit can be made and then pinned with an off-center cross pin drilled through the action/sleeve.

Color Code:
White - Barrel
Brass - Sleeve
Red - Action

Illinoyance · Nov 30, 2018

And later if you need to remove the barrel.....

CalG · Nov 30, 2018

SKS rifles have a variant with barrels pressed in and pinned to the receiver.

They work as well as the threaded type.

john.k · Nov 30, 2018

Dont Savage do this with one of their current CF rifles..........I think the barrel is swaged into the reciever. It seems the average customer fires less than 100 rounds in all the time he has the gun.

Don Nielson · Dec 1, 2018

I feel that you have no concept of a 60,000 PSI explosion going off inches from your head. D

BrandonOD · Dec 1, 2018

AK's use this set up. Changing barrels is a fairly lengthy process compaired to unscrewing the old one and screwing a new one in. The other way requires a press which can lead to a bent barrel.

CalG · Dec 1, 2018

I can see no useful function for the brass intermediate piece of the OP sketch. I can see reasons that suggest NOT to include it. More pieces to fit, reduced friction, etc.

The surface area of the base on the bolt is the thrust that must be considered. There are many "opinions" on just what that number might be.

BK6BR · Dec 1, 2018

SilveradoHauler said:
Way back in The dark ages when I designed actions I made a rather complicated Excell Spreadsheet that calculated bolt back thrust and locking lug stress for most actions. Surprising to say the least! Some of the guys using big cases like 338 Lapua and Rigby are right on the edge of disaster.

Do you mind to go into more detail? This is something that I have never considered. In reloading I’ve made some hot loads that crush the brass/primer but have never considered the bolt becoming a projectile!

CalG · Dec 1, 2018

SilveradoHauler said:
As Patton Said to Rommel: "I read your book".

The Supplement to Modern Gunsmithing, the two Volume set by James Vergil Howe, mentions some experimentation during WWII. They fooled with shrunk on barrels in 30 cal. Hmmm The shrunk in section of barrel was found down range of the shooting location.

Threads are a mechanical joint and are there for a reason.

Read the history books, learn, do not repeat mistakes!

Are you discounting the 10s of millions of AKs and millions of SKSs in your dismissal?

Perhaps "shrunk on" is inferior to "pressed in". I know press fits can be quantified.

CalG · Dec 1, 2018

SilveradoHauler said:
Way back in The dark ages when I designed actions I made a rather complicated Excell Spreadsheet that calculated bolt back thrust and locking lug stress for most actions. Surprising to say the least! Some of the guys using big cases like 338 Lapua and Rigby are right on the edge of disaster.

Did your calculations include the expanded brass retention on the chamber walls as a function of case taper?

75sv1 · Dec 2, 2018

CalG said:
SKS rifles have a variant with barrels pressed in and pinned to the receiver.

They work as well as the threaded type.

I think this was on the cheaper made ones. I heard they did not last long. Also, the round used is a low pressure round. Works on .22s though.

CalG · Dec 2, 2018

75sv1 said:
I think this was on the cheaper made ones. I heard they did not last long. Also, the round used is a low pressure round. Works on .22s though.

[FONT=Arial, Helvetica]"The later Chinese SKS, 1970's -1990's, used an even less machined rear sight assembly and eliminated the barrel lug. The barrel was pressed into the receiver and held in place with a pin. These were used on both Military and Commercial versions of the SKS."[/FONT]

SAAMI pressure spec 45K psi

sealark37 · Dec 2, 2018

The communist nations used the press fit because it was cheaper. Our side threaded the breeches because it was stronger and thus, better. I would say, "Breech up your rifle as you wish". Regards, Clark

MilGunsmith · Dec 2, 2018

I have seen the AK's assembled in Bulgaria, they have the barrels pressed into an undersized hole stretching the receiver, then pinned. The press is similar to a log splitter. The AK is not designed for a replacement barrel, the barrel and receiver have the same lifespan. Our weapons are designed to be repaired, the AK's are considered to be disposable.

75sv1 · Dec 3, 2018

CalG said:
[FONT=Arial, Helvetica]"The later Chinese SKS, 1970's -1990's, used an even less machined rear sight assembly and eliminated the barrel lug. The barrel was pressed into the receiver and held in place with a pin. These were used on both Military and Commercial versions of the SKS."[/FONT]

SAAMI pressure spec 45K psi

The latter ones had stamped trigger guards and some other missing items. I was told they did not last as long and did not function as well. I bought a paratrooper model. Machined steel trigger guard. Also, as for military, some of the foreign countries consider their enlisted expendable. Also, how long did they expect a rifle to last under battlefield conditions? A lot of mausers survived. Others were buried under Russian mud.

I would look at the Colt Sauer action. Sort of the same premise. A shank constrained in a bore.

wesg · Dec 3, 2018

I would look at the Colt Sauer action. Sort of the same premise. A shank constrained in a bore.

Pretty sure my 458 is threaded. Would have to extract it from aux storage to verify.

Later and current Sauers have a clamped breech, but the locking lugs are integral to the barrel.

75sv1 · Dec 4, 2018

wesg said:
Pretty sure my 458 is threaded. Would have to extract it from aux storage to verify.

Later and current Sauers have a clamped breech, but the locking lugs are integral to the barrel.

I've only heald one. I didn't read that section on Ottersons book thoroughly. Looking into the barrel changes the dynamics.

Chip Burns · Dec 4, 2018

This is a subject that will start arguments, but never settle anything. The ultimate fit will come from freezing the barrel in dry ice and alcohol, while heating the receiver ring with an induction coil. If things do not go all the way home, it will not anytime in the future. The finish of the mating surfaces enter into the retentive abilities. A neighbor shot himself in the face with a Win. M97, when the locking lug snapped off from the bolt. He got two black eyes and a long cut on his cheek. If the barrel creeps forward .002” on the first shot, your headspace increases, and the length of engagement decreases by that amount, likely causing more axial movement.
If Winchester, Remington, Savage, and the others thought that it would work, and save fifty cents per rifle, it would be common practice. A brief view of the world as I see it. ;-)

75sv1 · Dec 5, 2018

The OPs use of a brass or copper sleeve seems to take the place of a brazed joint. Right theory, wrong practicality. Brazing and soldering work on and interstitial bond. Usually only .001 clearance or slip fit. After that the brass or tin is holding the forces. So, the barrel in this case would stretch forward.

GGaskill · Dec 5, 2018

The reference to brass in the OP is simply the color used to identify the sleeve, not the material used. But it is unclear why he wants to use a sleeve at all unless it is to fill the action threads.

If you're going to do a press or shrink fit, why add another layer?

Sleeving a barrel tenon

Plastic

Attachments

Stainless

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Aluminum

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Hot Rolled

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Stainless

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Titanium

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Hot Rolled

Titanium

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