Interchangable chambers

[grumble]

Savage has a good deal for swapping barrels and bolts to change calibers and chamberings. You can buy 308 Win inserts for a 30-06 and several other chamberings can use inserts in a similar manner.

So, why can't a barrel be designed with a "universal" chamber for that particular bore? For example, a 30 caliber bore should be able to shoot everything from a 30 Carbine to a 300 Win Mag if the chamber was properly machined for an insert of the proper size.

Is there some reason a universal insert couldn't be machined to proper tolerances to allow a precision fit into a universal chamber?

[nighthunter]

There are a lot of things to consider here ... such as twist rate and bullet length. Velocity is another question as well cartridge pressures. Hell .... there is a whole lot to consider. Don't forget cartridge capacity and bullet weight.
Nighthunter

[grumble]

You're right, nighthunter, the trwist would have to be a compromise of some sort to accomodate varying lengths, weights, and velocities of different rounds. Everything else though, from headspacing to leade, to throat sizes would be accomodated in the insert.

Only the rifling would be compromised for the middle ground between short and fast bullets and long and slow bullets.

[bruce drake]

Perhaps over time, the universal chamber would begin to suffer erosion between itself and the barrel, sort like the Mausers that were sleeved from 7.65 Arg to 7.62 NATO. The barrel's bore eroded around the end of the insert over time. So taking that plan to the Universal Chamber (UC) with the various chamberings (I'm envisioning several different UC inserts for one barrel.) available and the shooter devotes himself to shooting 308 WIN until he got his favorite loads developed (perhaps several years down the road) and then switchs to 30-30 Winchester (Now we are talking about modifiying extractors to handle rimless and rimmed cartridges as well), the shooter will see a difference between the 308 WIN UC insert and his 30-30 UC insert.

So in a long way to say this, you are shifting the headspace issues from the cartridge to the UC. Variant headspaces are not my cup of tea.

Now, that is my opinion on this and I'm sure someone more learned than me can go into more depth with this.

Bruce

[grumble]

That's a good answer, Bruce, something I hadn't thought of. The joint between the front of the "UC" and the back of the barrel would be prone to more wear from powder gasses because of the required sharp edges at the juncture.

Extractor issues could be accomidated, I think, like Savage does with their different bolt heads.

[David R]

My dad says if it does both, you usually get the best of neither.

[RugerFan]

Grumble,
How about chamber adapters? You may be interested in the following link:
http://www.mcace.com/adapters.htm

[Buckshot]

................A problem I see besides erosion which 'might' be mitigated to a degree by material, or a crush washer between the UC and barrel proper, would be the varying distance between the bullet and rifling.

Assume the easiest way to make the UC would be to have the base of the cartridge (any of the various cartidges) at the back (front being in the barrel) of the UC. Obviously the bolt is going to stop and lock up at the same place each time, right?

So in one you have a short lil ole 30 M1. The bullet has to run up through maybe 1.5" of smooth throat before encountering the leade and rifling. It would have to be so if the same size UC were to also handle the 300 Win mag, say with IT"S slug right there at the end of the UC.

A bit of fanatsy here:

If the various UC's were to be rifled over the otherwise smooth portion, each could be inserted then a rifled positive fitted and the UC rotated to allow the positive to match the barrel and slide in a bit. The UC is then marked for final machining to match a (however it might be done) barrel to UC locking devise.

The UC then HAS to be inserted only one way so it's, and the barrel's rifling match. A thousandth or so mismatch with a FLGC might not be an issue. Might not be so swell with a cast slug.

Great idea though!

..................Buckshot

[Trailblazer]

What you need is a loong receiver ring. Then you make the joint between the adaptor and barrel at the end of the neck. Picture a 98 Mauser with the c-ring to drop the insert against and then the long receiver ring that the barrel threads into at the front to clamp the insert between the c-ring and the barrel. I guess you would need a precise fit and some kind of tapered joint to line things up and seal gas pressure. Details! Details!

[grumble]

Yeah, that's kinda what I'm wondering about. I wonder if the rifling would really have to match up perfectly, though -- an eighth or 3/16 inch of room between the rifling of the insert and the barrel's rifling, assuming a smooth taper, shouldn't cause too much trouble since the boolit would be moving pretty slowly at that point. I don't know if obturation would be sufficient to "seal up" the mismatched rifling marks on the boolit or not to prevent gas escaping along the sides of the boolit. Perfectly matched rifling would be the best solution of course, if it could be done.

Oh well, that what brain farts are for, to disperse in the wind. <G>

Ruger Fan, yeah, that's kinda sorta what I was thinking, except with a rifle made to work for those inserts. My thinking would also require some sort of common magazine, probably a removable mag with a "universal" head machined for the various types of ammo. Obviously, a single shot would be the easiest.

[StarMetal]

There's another kind of adapter that I've seen. Lets say, for example, we have one to shoot a 32acp from a 30-06. The way it works is the adapter looked like a 30-06 cartridge. The 32acp fits way up into the adapter and an 0-ringed insert with a firing pin nipple on it is inserted behind the 32acp. This is chambered like a regular round and also extracted like one. The firing pin hits the insert which in turn hits the 32acp primer setting it off. In this type of adapter the bullet doesn't have as long a freebore to travel to hit the rifling. In some instances the adapter could be minus the neck and the smaller round being fired protrudes from the should to be the neck and thus positions the round as though the normal cartridge was present except with a smaller lighter bullet.

Joe