Anybody do chamber castings?

[Travis73]

I have a Type 38 Arisaka that has been sporterized. So supposedly it should use the 6.5 Jap cartridge. I've never fired it.
I've toyed with the idea of having the rifle rechambered to a different 6.5 cartridge. I wanted to check if the action and magazine were longer enough for the 6.5 Swede. So I put a few rounds in the mag. Awesome! They fit!
Now the part that's got me wondering: The 6.5 Swede would also chamber!
The last little bit of cycling required a firm push but nothing outrageous. Looking at the cartridge dimensions between the two, I don't think this should be possible. IF it is chambered for 6.5 Jap. Please correct me if I'm wrong on this.

 

[MoBoost]

I have a Type 38 Arisaka that has been sporterized. So supposedly it should use the 6.5 Jap cartridge. I've never fired it.
I've toyed with the idea of having the rifle rechambered to a different 6.5 cartridge. I wanted to check if the action and magazine were longer enough for the 6.5 Swede. So I put a few rounds in the mag. Awesome! They fit!
Now the part that's got me wondering: The 6.5 Swede would also chamber!
The last little bit of cycling required a firm push but nothing outrageous. Looking at the cartridge dimensions between the two, I don't think this should be possible. IF it is chambered for 6.5 Jap. Please correct me if I'm wrong on this.

I've done it using candle wax. Oil everything, plug the bore with patch on wooden rod 1" or so from where you think the chamber ends, stand the rifle muzzle down, melt the wax and poor it in. It takes a long while to cool (20 minutes). Push it out the cast with the rod. The cast is not a as solid as over-the-counter specific methods - but it gives you very good idea, just don't go crazy with caliper pressure. Clean-up is easy, and if wax gets somewhere it shouldn't - you can just melt it out with quick sweep of a torch.

P.S. I did it on Arisaka that ended up being chambered in 300SAV and I had it rechambered in 308WIN.

 

[Travis73]

Do you think that the wax may shrink as it cools or will it maintain an exact shape?

 

[MoBoost]

Do you think that the wax may shrink as it cools or will it maintain an exact shape?

It might a bit, you are not trying to machine dies from the cast, you just trying to figure out the cartridge, right?

 

[Travis73]

No, not machining anything. Lol. Just trying to understand and do it correctly. I ask about shrinkage because the measurements I get seem small for a Swede but too loose for a Jap. The length seems to indicate its a Swede thought.

 

[MoBoost]

No, not machining anything. Lol. Just trying to understand and do it correctly. I ask about shrinkage because the measurements I get seem small for a Swede but too loose for a Jap. The length seems to indicate its a Swede thought.

Sounds like 260REM

 

[Shriner]

Travis73 you get some chamber casting metal from Rotometals $16.00 a lb(brownnells is much higher) to be sure , it melts at low temp and sets up in about 2 mins ,will give you true dim .I have done 3 castings and still euough for one more out the 1 lb I got.

 

[Shriner]

Travis 73 the numbers in my shooter bible guide to cartridges for 6.5 jap and 6.5 swedish mauser don't work out, the jap is a rimed case, the mauser is not. sm is .480 dia, jap is .451 dia

 

[Travis73]

Here's my diameter numbers:
Swede: neck=.290, shoulder=.435, base=.475.
Jap: neck=.290, shoulder=.410, base=.444.
Cast: neck=.295, shoulder=.430, base=.465.
(Cast base dia measurement taken above the recess where the extractor claw sits when the bolt is closed.)

The numbers don't quite match. That's why I asked about shrinkage of the cast.

 

[Travis73]

I took pics of the cast next to the cartridges in question. But can't figure how to post them.