One rifle, one barrel, 3 calibers capable?

[klover]

The SHTF rifle for $1000" thread got me thinking. I've come to the same conclusion about the utillity of a .44 mag Marlin lever rifle as did Md7. I even stocked some .44 ammo, but no lever yet.

Came across a nice weaver 3 x 9 vari x II on a 300 RUM. Definitely would be ok on a 1894 (when I find it) was my thinking.

I've long ago decided that I would never be without both an SKS and a shotty.Some 7.62 X 39 is always good to stock pile. For greater range SHTF (I can think of some what if's) I've been thinking about getting a .308.

So this 300 RUM looked as new, and it called me as I walked out the pawn shop with just a Kersaw knife. It said to me:" why don't you just machine some chamber inserts to carry both .308 and 7.62 x 39 and use those in me?".

I have not yet checked the bore details, nor did I check the dimensions of the chambers for this nesting idea. However, if the bore issue is ok, the cavernous 300 RUM should in all cases leave a nice wall thickness for the inserts. Perhaps you guys (gals) know where I can buy some already made?
Some of you might know these bore details well, and can save me the trouble of looking them up.

My idea is to NOT let my gun collection grow... admitted I am powerless....

 

[RecoilRob]

What you propose would be difficult for several reasons. First, you would need to secure the chamber insert in the chamber. Tight enough that breaking the 308 loose after firing doesn't pull the insert out.

Once it is secured, how do you remove it to change calibers? And, is the RUM case head the same size as the smaller rounds? If not, a bolt change would also be needed.

How are you going to feed the small rounds? Or single shot manual feeding only?

Bore dimensions are close enough to work but I'd opine that the other problems are plenty enough to make this dream a difficult one.

 

[Brian Williams]

Most inserts are locktited in and almost as hard to remove. OK idea, but would be hard to get to work easy.

 

[klover]

I just checked for the .308 winchester. It leaves about .o4o insert wall thickness around the cartrige body.

I'm thinking to make several inserts, and pull them with the spent winchester round with the bolt ejector. There is only .o33 less radius on the winchester rim for the ejector to travel, so I suspect it will hook the case. Since both are belted rounds, they must head space on the taper. The only critical dimension to hold would be between the 30 degree taper and the 20 degree taper. This distance is .824 inches in length at the crimp diameter because the RUM is such a long cartridge.

Either the both parts will eject (I suspect) or the insert will remain in the chamber. If the insert remains, I'm still in business. If the insert pulls, I could drive the spent case out into a turned sleeve with a drift through the case mouth.

There would be some "free" space in front of the insert of .523 inches. This space is of .346 diameter which normally is the crimp on the RUM bullet.

I would very much welcome someone to poke holes in this idea even though I am now the proud owner of an experiment.

Thank you all.

 

[Bigfoot]

22LR, 22 Long, 22 Short in a Remington pump action.

In your quest for a centerfire gun that will shoot at various velocities I propose a press, a loading manual and some H4895, XMR5744, SR4759 or Blue Dot.

 

[klover]

Looking to make this work specifically with 300 RUM, 308 Winchester, and 7.62 x 39.

 

[RecoilRob]

I was trying to be brief in my first post and HAD thought of an insert per smaller cartridge that would be loaded, fired and ejected as one.

You would need a bunch of them to be useful but there is a serious problem with that idea. On high pressure CF rounds, it is imperative that the brass expand and grab the chamber wall. This provides a good seal for the propellant gas and, of equal importantance, greatly reduces the thrust applied to the bolt and locking lugs.

A floating chamber insert will cause excessive pressure to be applied to the boltface. This method HAS worked on sub-caliber conversions where the substitute round is much less powerful than the original and therefore doesn't stress the boltface abnormally.

Again, great idea but I'm still leaning toward the not workable side.

 

[Erinyes]

Looking to make this work specifically with 300 RUM, 308 Winchester, and 7.62 x 39.

Uh, unless you're reloading your 7.62x39, it has a different bullet diameter (.310in). Not a good idea to fire that out of a .308 bore.

And if you are reloading, why not get the .300 RUM and just load three different power levels?

 

[klover]

Thanks Erwinyes, I was trying to remember the actual diameter of a 7.62 x 39.
As for loading low power loads, I was thinking to avoid reloading and to allow use of the very popular factory .308 Winchester. It is only $1.00/rd vs. $3.00 per round (and hard to find). I'm curious about factory recoil in my new toy . Perhaps the good way to reduce recoil is as you sugest and simply reload.

Thanks to RecoilRob as well. I doubt that .o4o wall would not stretch against the chamber, but as you mention, it may very well over load the bolt since having two sliding surfaces is a way to reduce friction. I would not like to eat a bolt shoved by a measley little .308 explosion .

Tinkering thinking often gets me into trouble. Lots of wonderful, clear headed folks here on THR

 

[dfaugh]

Different head sizes...different bullet diameters...It gets ugly real fast (not that it couldn't be done)...

But, how about what I'm contemplating?

Savages has easily interchangable barrels (with the right tools, but you only gotta buy 'em once). Keep action, scope and stock as I like and change barrels at will (checking headspace, with gauges for each caliber). With all the different cartridges with .473 diameter, I could go from .22-250 to .35 Whelen...AND, the bolt face is also easily changed, so you could also add some different (magnum) cartridges without too much fuss. Feeding may be an issue, with some requiring magazine modifications, or use as a single shot.

 

[db_tanker]

Other than the 22 rimfires, the only three calibers that come to mind would be...


38 spec, 357 mag, 357 max
44 spec, 44 mag, 445 supermag
45 colt, 454 casull, 460 S&W

The first two can go in a contender carbine or pistol...single shot but it would still work...

second would have to go in an Encore carbine/pistol...

THAT would be the cheapest path you wish to follow...AND the nice thing would be that you only really need ONE set of dies with that path...just simply crank out the die an appropriate amount for the larger capacity case.

D