Patching the 7.7 Arisaka

[blixen]

I've been trying to get a Arisaka sporter to shoot CBs. It has a .316 bore. Shoots jackets well but, throws my .314" boolits into pie plate-sized groups.

Here's the background: http://castboolits.gunloads.com/showthread.php?t=237437

. I'm going to follow a suggestion to try paper patching. Never done it before. So I'm posting in this forum.

I think I've got a recipe that might work. I size bullets out of the Lee Brit .303 mold to .310". Then, I patch them with two wraps of notebook paper. When they dry, I lube with 45/45/10 alox/paste wax/thinner.

Push them through a .316 sizer and they spring back to .318-.319".

They seat snugly into my fired cases and the neck likely compresses them down another .001.

To do: work out a template for the angle seam and get the knack for rolling, so the PPs are consistent.

[Nobade]

It is important to not confuse bore diameter with groove diameter, when discussing paper patched boolits. The core should be .001" or so over bore diameter and the finished product fit the throat, usually a couple thousandths over groove diameter.

If you patch a .310" boolit and size it to .316" you are likely to distort the core and tear the patch. You will likely want to make the initial sizing smaller, just over whatever the bore size is on that rifle.

-Nobade

[pdawg_shooter]

+1 on what Nobade said. Bore diameter +.001/.0015 before patching, Throat diameter after patching. Seat the bullet INTO the rifling a bit and use a slow enough powder to give 100%+ load density. Works for me anyway.