.264 or .268???

[Cypress]

OK, I'm pressing ahead with my soon to be possibly more worthless Type I Arisaka project and have realized that the 6.5 Carcano round is .268 and my 6.5 Jap should be .264 but it has me wondering if my bore is .268 since it has a Carcano action. The bore is pretty bad in the last 1/2 inch of the barrel so I'm gonna try a home cut and crown job. Do you think I would actually be able to tell if it was .264 or .268 originally with calipers. How much more pressure will 4 thousandths create if I test fired .268 bullets in a .264 barrel.

 

[blackthorn762]

I would slug the barrel to get your actual bore specs. Use a fishing weight that is no more than .270 in diameter, lube it up real well, and pull it through the barrel. Then caliper the groove impressions to get your actual bore diameter.

As far as how much the pressure will increase using a .268 bullet...I am by no means an expert, though I my first thought would be that it would depend on condition the barrel is in along it's entire length, not just the last two inches. If that section is as bad as you say it is, I have to wonder what the rest of the bore really looks like. Maybe someone with more experience than I can chime in here and give you better anwser and teach me something at the same time.

 

[Cypress]

It looks like the guy that cut the barrel off last time used a crowning tool with a poorly sized pilot and it removed most of the rifling at the end. I'm going to cut this portion off?

 

[rcmodel]

The Type I Arisaka Carcano is chambered for the 6.5x50mm Jap cartridge, not the Italian 6.5x52mm Carcano.

Don't get the two confused!

rcmodel

 

[Cypress]

Not getting the two confused. Just wandering what the odds were that the makers were tooled up to cut barrels for the Carcano round and went ahead and and cut the Jap barrels too big.

 

[Cypress]

Just thought maybe the contract laborers cut some corners!!! Gonna slug the barrel tonight?

 

[Cypress]

Slugged the barrel 3 times and came up with .270-.271. Looks like I may have a sure nuff Japanese Carcano. Kinda narrows down my bullet selection. Gonna try some .268 from Hornady. If that doesn't work I think the project may get scrapped.