interference fit barrel?

I've been making some sketches for a turnbolt receiver. I've pondered the conventional screw-in barrel vs. the Savage style barrel nut, the second-design Arisaka takedown attachment, etc. The main factors have been my skill level and the equipment I have available.

While looking at some of the slide-and-pin takedown designs, I began to wonder... has anyone encountered a rifle with an interference fit barrel?

Back in ancient times, some ball bearing manufacturers made bearings with threaded inner races, to positively locate them on shafts. These were largely superceded by various taper attachment methods. These, in turn, are being slowly replaced by the "SKF oil injection method." This is also used for assembling built-up crankshafts with roller bearings.

Basically, you make your parts with whatever interference fit you select. One part (depending on what's convenient) has an annular groove connected to a port, which is then connected to a high pressure source full of oil. This can be anything from a grease gun to a 6000PSI hydraulic pump depending on the situation.

The annular groove feeds oil to the joint, spreading the pieces apart so they can be slipped together and aligned easily. Then the pressure is bled off and the parts clamp together.

For disassembly, you just pressurize the joint again and pull the pieces apart; no chin-ups on the barrel wrench needed. (and no need to cut internal threads at the front of the receiver!)

I have been told of some Mausers that have had to have the reciever bored to get the barrel out,they may have been interference fit. It doesn't sound like a good idea loctite will keep the barrel from comming loose if that is your concern.

Hi There,

I'm not sure exactly what you are getting at. If you are talking about an interference
thread fit, this has been done (I have one of those Mausers I had to cut the threaded
section of the barrel out of the receiver). If you are talking about a "shrink fit" type
interference, I have only heard of this done on some cheaply made .22 rifles. I don't
think this type of barrel retention would be practical on a high power rifle IMHO.

Good Luck!
-Blue Chips-
Webb

steyr uses a very heavy press to fit an "interference fit" in some of their high power "target" rifles, note that in these cases an longer receiver length and barrel shank is used compared to the threaded actions

the only practical way of rebarrelling these that I can think of would be to bore them out and thread the receiver for conventional fitment

as a WW2 expedient, some No4 LE rifles had a shrink fit for experimentation but I don't think any were ever issed

personally i'd go for a standard threaded fit or a savage type locking nut which has the sole advantage of easier barrel changes & refitting if that's what you're looking for

Langfur

Dave W,
Dry ice/heat would be easier/cheaper than the oil pressure method, but harder to reverse for further adjustment. Are you considering interference fit to avoid threading? Let us know how it works out.
F

PS: The Browning BBR uses some kind of a press fit arrangement; hard to rebarrel.

IIRC the browning full bore bolt actions have a hardened insert pressed into the mild steel tubing receiver.

The insert has threads to hold the barrel and the locking shoulders to hold the bolt, so the stresses of firing are taken in the conventional way through threads and lugs, all the press fit does is hold the parts in line.

Voere use a similar insert (I think it is stellite or something equally exotic and ridiculous) again pressed into a mild steel tube receiver, with a welded on recoil lug.

Light alloy actions like the Stolle Panda use a threaded in insert of pre hard 4140, which is effectivly a receiver ring in itself.

Sauer use a threaded reciever ring, but have a saw cut running lengthways up the bottom and a couple of clamping screws to tighten up and lock the threads.

I think that in centrefire, the only friction held barrels actually have the bolt locking into the breech end of the barrel, so again, no firing stress on the friction joint, I may be wrong.

I think that a friction joint is going to need tighter tolerances and surface finish than threading, so nothing gained.

The mauser inner collar in the receiver ring, with the flat breech face of the barrell butting against it provides a uniquely simple system for controlling case head protrusion and also strengthening the receiver ring where it needs it most. once your barrel is chambered relative to that breech face, just screw it in until it is tight against the inner ring and the headspace and head protrusion can be repeated each time, true, as the threads wear you will have the barrel rotating a bit further, but most people use scopes mounted on the receiver, so no problem.

if you must have open foresight or barrel mounted scope base, allow some way to adjust it back to vertical.

For locking the barrel in place, you could use a lock nut, or if you are using a longer thread in the ring, you could use a saur type clamp screw and split the front part of the threaded section.

Stuart Otteson's books have good discussions of most of these actions.

Keith

Interferance fiting could be an interesting technique, if the bolt locked to the barrel rather than the reciever. I don't think I would be comforatable with an interferance fit on a rifle where the bolt locked against a shoulder in the reciever.

Yes its possable to design an interferance fit that would work and have a generous safety factor, none the less I would not be comfortable putting my face behind it or my hand on the forearm.

If you still want to do an interferance fit on a mauser type system think about this. At the very least you would want a press fit that could conservitively handle the forces required to strip the threads in a comprable action. I think when you put the numbers to the design it will be impractical for most centerfire cartrages.

Remember, if a case ruptures you could have full pressure there for a fraction of a second while it vents. Think about that, 50,000 psi on a 1" circle. Its going to take a lot of friction to hold that back, especialy if the surfaces have any oil on them, and you have to assume that they will. Think about it, when you open the spout on the bottom of you air compressor to drain the water, the pressure does not drop to zero instantly. The same will be true if a case head seperates and vents gas into the gap between the bolt and the barrel. If a primer is pierced or a case seperates the gun must be able to deal with it without harming the operator. This is probably more likely on a home built prototype than on a proven production design.

If on the other hand you locked the bolt into the back end of the barrel, then the reciever is nothing more than a set of guide rails with a trigger mount. If the press fit does not cary a load during fireing your a lot safer. You could make a collet or any other simple arangement to snug the barrel into place.

I have a pretty good hunch that tight-fitting Mauser threads are not so by design. Weren't their barrels originally designed to abut upon the internal receiver ring collar, with a slight gap between the barrel shoulder and the front of the receiver ring? To make them both tight to the same degree would've added unnecessary difficulty to manufacturing.

Though the hardened, pressed-in ring inserts simplify receiver hardening, I'll take a pass on that method.

BTW, do any of you guys know whether the new Savage 40 Varminter has a threaded barrel? A mag writer (Layne Simpson?) has said that it does, but I'm skeptical. The receiver dia. looks kinda small, the ring is extra long, and there are pins going through it, and the barrel.
F

While looking at some of the slide-and-pin takedown designs, I began to wonder... has anyone encountered a rifle with an interference fit barrel?

Click to expand...

The Remington 710 series uses an interferance fit barrel. These are made in .243,.270,.30-06 and 7mm Mag and .300 Win Mag. It's a fairly popular rifle and its been in production since 2001.

I have one in the .30-06 and it is an exellent shooter having accounted for several deer.

Its been several years since they have come out, and I am not aware of any failures due to the fit up method of the barrel so it would seem that most of the fears posted here are unfounded. Remington would'nt be putting that design out if they even had a hint of a thought that there would be issues with them. Its one of the reasons that the 710 is so cheap, because of the manufacturing techniques used in building the rifle.

Does the 710 bolt lock up on the receiver ?? Or on the barrel itself ??

The SKS rifles have a press fit barrel. As do the AK family of rifles too maybe ??

Bill

Mausers properly chambered seated on the inner ring and tightened a little more also seated it to the front of the receiver.
Butch

willbird said:

As do the AK family of rifles too maybe ??

Bill

Click to expand...

My Romanian AK barrel is a press fit and then is pinned.

Steve.

BL,
The inner ring being the tightest fit precludes easing the job of pulling an unwanted barrel by taking a (partial depth) cut with a parting tool/saw just in front of the receiver. Well, I reckon it'd help a little...
F

Release cut

I had to take a cut in the barrel just in front of the receiver to pull the barrel from my Chinese "SKS". The thread length is just under an inch.

Usually better to scrap a barrel than to bend/break a receiver.
F

You can save the tight barrel by cutting in front of the receiver ring with a thin cutoff tool. The barrel will spin off easily and can be saved for reuse by cutting for one more turn and re chambering.

The WW2 German Gew/Kar 43 semi-auto rifles used an interference fit barrel. They were chambered in 7,9x57 Mauser and were made in the hundreds of thousands by several firms.

Hydraulic mounted barrel

Hi Dave,

There is one (at least) design incorprating the basic principle of the SKF sleeve couplings you refer to.

Strasser RS 05. A relativley recent design with many things common with Blaser R93. Horst Strasser is one of the main designers behind the Blaser R93, which can be easliy seen in the RS 05.

The strasser has a built in highpressure pump that you can lock/unlock the barrel in the reciever with. As with most of this kind of designs, the bolt head locks in the barrel.
As for this Strasser rifle it incorprates a lot of more modern features. QC-barrels, boltheads, straightrepeating, QC-scopemounts etc etc.

Personally I don´t find this solution efficient in sentence of cost/design compared to the Sauer design, it might however be more userfriendly for not-so-handy-man....

I couldn´t find a good link right now. The only one I find is to this german page which has some more or less selfexplanatory pictures. Maybe someone else has some good links?

http://www.lima-wiederladetechnik.de/Waffen/Strasser-05.htm

Soo.... there is not much news under the sun...

There is German conversions of the M98 action to takedown, where the threads are bored out, and pieces of steel is welded on underneat.
The bolt is locking directly in the barrel and the barrel is secured to the action in the same manners as a Sauer 202.

When it comes to Blaser as I udnerstand it Horst blaser sold and left the company long before the R93 was developed.

Technika

Thanx Technika for clearing up my blurred version.
Must have been something in the food that evening, or could it been in the drink? ;-)