Unique question: Converting a Murata type 13

[Ratrod318]

Hello. I’m looking for any advice on a possible general direction on converting a single shot rifle to a different caliber.

I know this is a purist’s nightmare, but I’m interested in the possibilities.

the rifle in question is a Japanese Murata type 13, currently in 11x60mm Murata caliber. It is a single shot rifle.

I have a attachment to the model 13, (my favorite book and tv character used one.)

I was going to go through the trouble of reloading the rare brass. But now I’m interested in upgrading it. I collect guns to shoot them, 11mm Murata is a relic.

my questions:

1. Murata 11mm is .43 inches, so could I put a .44 or .45 barrel on it. (Maybe.45LC??)

2. What possible calibers might work if I change the barrel?? Any possible ideas,(or at least a general direction?)

3. It’s a single shot rifle (so no elevator or magazines to modify) so what do I need to keep in mind for the bolt to still be able to feed the new the round? (I’m not sure how it feeds)

4. final question: the murata is originally a black powder cartridge. I imagine that a majority of the cartridge pressure when fired escapes through the barrel, but what are the dangers of the mechanicals, of the bolt and other things behind the cartridge being damaged with modern smokeless cartridge?

I know that this question is a Murata purist’s nightmare.

But I’m a heck of a machinist, and I’m interested in trying.

 

[LoonWulf]

I don't know the Murata, but USUALLY the concerns for barrel fitment and cartridge used on a single shot would rim diameter, and expected pressure/bolt thrust.

 

[NIGHTLORD40K]

Welcome to the forum!

Why not make a cartridge adapter or chamber insert for, say .223 or 7.62×39? You could epoxy it in without cutting the original barrel and pressure shouldn't be a problem because the insert/adapter will reinforce the chamber.
Perhaps bore it out and do a full length sleeve for .22LR?
Or, maybe a .410 shotshell conversion?

In any event, this sounds like a fascinating project, Muratas are rare in the US- I've only seen them in books. Please keep us updated. Pics always welcome!

 

[edwardware]

This practically begs for a barrel insert to completely reversibly convert to a common low pressure cartridge. I'd start at .22LR or .38Spl.

 

[Ratrod318]

Welcome to the forum!

Why not make a cartridge adapter or chamber insert for, say .223 or 7.62×39? You could epoxy it in without cutting the original barrel and pressure shouldn't be a problem because the insert/adapter will reinforce the chamber.
Perhaps bore it out and do a full length sleeve for .22LR?
Or, maybe a .410 shotshell conversion?

In any event, this sounds like a fascinating project, Muratas are rare in the US- I've only seen them in books. Please keep us updated. Pics always welcome!

Thank you so much for the ideas. I was hoping to pick peoples brains for possible on ways to convert calibers on the Murata.

You gave me a great direction to go. I had no idea barrel liners existed, but after researching what you said I see there is definitely options.

A barrel liner is absolutely the thing to try.
I just have figure out suitable calibers.

I think a .223 would be awesome, the fact it’s a extremely fast little bullet, makes me nervous. But with a barrel liner the Murata would be reinforced, It might handle it.

 

[Ratrod318]

This practically begs for a barrel insert to completely reversibly convert to a common low pressure cartridge. I'd start at .22LR or .38Spl.

Thanks for the idea about using a .38, that’s a very low pressure round. It’s definitely a possibility. This forum is great, I never would have thought about putting a barrel liner in to change the caliber.

 

[NIGHTLORD40K]

 

[.455_Hunter]

I would avoid anything that provides pressures much above 11mm Murata BP levels. Its not just the chamber walls that bear the load- the bolt face does too. Lined .38 special would be a good and fun choice.

 

[Ratrod318]

I would avoid anything that provides pressures much above 11mm Murata BP levels. Its not just the chamber walls that bear the load- the bolt face does too. Lined .38 special would be a good and fun choice.

Thankyou so much for the advice and warning about not exceeding the original black powder specs.

I figured out the 11mm x60 Murata specs were:

420 grain black powder
@1487 fps
With 2,060 ft pounds of energy

so that right there is the limit,

thanks for the advice, 38special is definitely safe, it’s half the power of the Murata cartridge.

38-55 probably would be safe also,
But definitely, .38 special is probably what I end up using.

 

[.455_Hunter]

Thankyou so much for the advice and warning about not exceeding the original black powder specs.

I figured out the 11mm x60 Murata specs were:

420 grain black powder
@1487 fps
With 2,060 ft pounds of energy

so that right there is the limit,

thanks for the advice, 38special is definitely safe, it’s half the power of the Murata cartridge.

38-55 probably would be safe also,
But definitely, .38 special is probably what I end up using.

Nothing wrong with BP equivalent .38-55, just harder to source components.

It's not really the KE of the loading, but the chamber pressure that is the concern.

 

[Ratrod318]

Apdate:

I got help from a gunsmith with experience in safely adapting a modern caliber to a old gun.
He’s actually adapted a Murata before.

we’re going to go with .32 S&W

 

[Jim Watson]

 

[NIGHTLORD40K]

I think Jim is laughing at the idea of .32S&W as "modern".
Hehe...I chuckled at that one myself. But hey, at least its doable!
You could probably at least go .32S&W Long, and still shoot the short cases if necessary.
In a pinch, theoretically, a .32 S&W can shoot .32 ACP as well, though it is quite a bit higher pressure.

 

[Jim Watson]

No, I was laughing at sleeving an 11mm rifle down to .32 pistol.

What for an extractor?

 

[Ratrod318]

I understand the humor,
.32 s&w, isn’t real modern.
(But more modern than the 1885 rifle it’s going in.)

 

[Jim Watson]

Nope. .32 S&W came out in 1876 or 1878 depending on your source.
Now it took them til 1896 to produce .32 S&W Long.

 

[Ratrod318]

No, I was laughing at sleeving an 11mm rifle down to .32 pistol.

What for an extractor?

I may have completely misunderstood the gentleman that is doing the gunsmithing, so forgive me if sound dumb.

But it sounded like he was going to use special techniques to make Murata shell, out of proper material, one that the .32 can fit in. (The 11mm murata acting like a sleeve.)

Apparently he has done it before with Muratas.

the guy designs artificial limbs and stuff for his main job, so I assume he’s smart.

regardless, the modification will be easily reversible if I don’t like it.

 

[NIGHTLORD40K]

Sounds like a "cartridge adapter," wherin the outer shell is the same dimension as the original cartridge case and a smaller cartridge is inserted into it. The original feed and extraction mechanisms will still work normally with these, however velocity will be very low and accuracy is usually not great.
Still.....it will go bang and no modifications to the gun are needed.
Cant hurt to try it, good luck and keep us posted!