7.62X39 in a .308 bore?

[sxsboy]

Has anyone here ever run into problems shooting .310/.311 dia bullets down a .308 barrel? Typically: shooting surplus 7.62 ammo in a Ruger mini-30. Doesn't something like this cause undue pressure problems? I'm interested becaues I was thinking about re-barrleing a 6.5 Carcaino for my young nephew as a deer rifle for next season. I have a Rem take off barrel in .308 and after I remove the whole chamber there will be plenty of shank left for the Carcaino action. I tried 7.62X39 ammo in the clips and they fit perfectly. So for next to nothing I could have him into a sweet little deer rifle. But... I'm worried about the undrer bore condition with a questionable at best action.

Also has anyone ever re-barreled a Carcaino? My NRA barrel shank diagram lists it as "about" 14 tpi. My thread pitch gauge sort of rocks back and forth @ 14 but is much better than the 13 and 15. Any tricks to getting a good fit w/o a lot of play and or lock tite? ???

Thanks for any suggestions or comments, Joe

 

[spclark]

... I'm worried about the undrer bore condition with a questionable at best action.

You may have answered your own question with that statement.

Complicating your risk would be steel-jacketed ammo out there which would be much less forgiving than gilding metal jackets when fired into an undersized bore.

If it was a project for your own personal use you'd have more latitude. As you mention involving another individual I'd err on the side of safety, perhaps by buying a properly-sized new barrel for the project.

 

[tdnichols]

I have a savage barrel that I reload for..using 308 bullets...no surplus ammo and I shoot it sub-sonic. It started life as a 308 win barrel..anyway I don't shoot the surplus ammo and shoot subsonic and lead bullets only.

 

[p17enfeild]

Carcaino rifles ? iam not surebut i think must of them are metric theads 1.75 mm pitch this works out at very close to 14 and 1/2 tpi but still will out interchange ! id fid some one how can do metric threads

 

[Halfnutz]

While I think your intentions are admirable, I also think the Carcano has a poor reputation for strength.
None the less, I have an Encore pistol chambered in 7.62x39. I was also worried about using surplus ammo in it, not that I planned too but wanted to know if it was safe irregardless. A call to Tompson Center claimed that it would be safe. I have tried it with no ill effects.

 

[Laurie]

"Bolt-Action Rifles ..... Expanded 4th Edition" originally by Frank De Haas and now updated by Wayne van Zwoll (Krause Publications large format paperback) has barrel shank drawings as an appendix and shows the Carcano's as 1.065" dia with twin-step short smaller diameter stubs of 0.968" and 0.835" plus a fourth even smaller measurement shown that as a technically illiterate type I don't know what it refers to. Threads are described as "Aprrox. 14 V tpi".

It looks one of the most complex barrel-face arrangements of the many shown in the book, so doesn't look a great prospect for the home-gunsmith ...... but as I said, I'm not in a position to make an informed judgement!

The 0.308" v 0.310" barrel groove diameter difference shouldn't be a great issue - the Ruger Mini-30 has always used US / European 0.30 calibre dimensioned barrels, not proper Russian 7.62mm designed for 0.310-.311" bullets. However, the Mini-30 is a very strong action, while the Carcano used a slightly modified Mannlicher design that dates from the 19th Century. De Haas says they were well made with good quality steel and reasonably strong, but notes that the Italian cartridges (likewise 6.5 Mannlicher-Schoenauer) were loaded to a maximum pressure of only around 40,000 psi. US SAAMI standards for the 7.62X39mm Russian in factory cartridges are for an average maximum pressure of 50,000 CUP, (copper crusher) 45,000 psi (Piezzo transducer), but you'd probably be safe enough with mild handloads.

With some experience of the 7.62X39mm, what I would say is that you'd have to be very careful using some surplus east European ball ammo, which is loaded 'hot' and gives 200-250 fps more than the standard Soviet era M43 specification. East European stuff mostly uses steel jacketed bullets too that will likely push pressures up in a tight bore!

Good luck!

Laurie,
York, England