cast for 6.5 Robts ?

[JonB_in_Glencoe]

I recently purchased a Jap Mauser converted to 6.5 Robts.
It has the original Military bbl. and the bore looks nice and shiney,
and the rifling looks crisp and looks to have a very quick twist rate.
The seller claimed it has a twist of 1 to 7.1 (I've learned to take info like that with a grain of salt.)

I recently ordered the 2 cav LEE mold from Midsouth, 170 gr. for another gun. My 6.5x55 swede, will that boolit be too heavy for the 6.5 Robts ?

A close friend and amateur gunsmith said I should use
a bullet about 130 to 140 weight.

Feel free to post your opinion, if you think my friend may not be correct.
I personally don't know where to start.

I did place a WTB add in the sellin' and swappin' section for a 130 to 140 grain mold if anyone reading this has one to move.
Jon

[HamGunner]

I have a 6.5mm Jap x.257 Roberts carbine that I like very much. It has a .269 bore and most are larger than .264 so your bore must be slugged in order to know your bullet diameter needs. I have a modified Lyman 266469 Loverin single cavity mold that now drops a .270dia. bullet that works well in my carbine. I throated the chamber so that the long 146gr. bullet can seat out long enough so the gas-checked base is not seated below the bottom of the case neck.

I reamed my .266 lube sizing die out to .270dia. so it can lube and size bullets for my bore. You have plenty to consider before you just start casting bullets, that is, unless you have already done the homework.

By the way, my carbine likes the .269dia. Hornady Carcano 160gr. jacketed roundnose bullet using RL-15 at about 2,450fps out of the 20" barrel.
Buffalo Arms sells these plus another lighter weight spitzer.

Oh, the twist rate should be about right for the shorter 145-146gr. bullets with the slower velocities that most shoot with cast. If the velocity were cranked on up then I suppose the much longer 170gr. bullet might do fine.

[madsenshooter]

Some Jap rifles do appear to have a tighter twist than others. Load data for the 6.5x257 and 6.5x55 should be practically interchangeable, case capacity is so near to being the same. The metford rifling of the Jap can be a problem, requiring a harder cast boolit. Groove diameters vary widely, most seem to be about .2675, but I find an occasional .264. Slug your bore first, so you know what size mold to get. The Midsouth casts a boolit that is marginally stable in the Swedish mauser, so it'd be nice if your Jap barrel does have that tight twist.

[Bret4207]

I've ended up buying a 270 mould for my 6.5 Roberts. Still have to get the sizer fixed up, but that's an option.