Need some info

[teraph]

I have everything lined up to reload 30-30, but I ordered a .308 sizer not a .309. This being said, what is the down side to using it with my gas checked cast bullets in a 30-30?
Thanks

[Jumping Frog]

If a bullet is sized too small, that can lead to the burning gases escaping out past the bullet, causing "gas cutting" of the lead and leading to heavily leaded barrels.

You actually run more of a risk with a gas-checked bullet, because an undersized normal lead bullet still has the possibility of obturating. Bullet obturation happens when the pressure of the expanding gas is high enough to deform the bottom of the bullet, causing it to expand and seal the bore and engage the barrel's rifling. It is like putting a lead bullet in a vise and hitting it with a hammer. The bullet gets shorter and fatter.

A copper gas check won't obturate in the same way because copper requires higher pressures to deform.

Bullet sizing is one of the most critical variables in getting good lead bullet performance at minimal leading.

What kind of rifle are you loading for, and have you slugged the barrel? If your barrel is slightly undersized, you may be OK. If it is an old .30 cal that is oversized, you may need even larger than .308.

[aggie67]

Get some soft lead--round ball is usually pure lead--larger than bore and push through to slug the barrel. Measure the depths of the grooves (larger diameter) and my best luck with .30 cal bullets is to size .001 or .0015 over to cut out leading competely.

If you are using the lee push through sizer, you can increase the bore easily without machine tools. Take a cast bullet that is oversize for your sizer and put valve grinding compound on the side and little on nose of the bullet and push them through as if you are sizing. Do this a couple of times, clean (depends on whether you use water or oil based VGC, use water or solvent) and size a bullet and measure.

I encourage you to measure slugs with a micrometer, not a caliper. It is easy to get false readings with a caliper with lead slugs. If you do not have a mic, perhaps you have a friend, neighbor or mentor who can loan you one. You can pick up a fairly inexpensive mic at ENCO or even sears. Would loan one if you were close to me. I also have a special molt that is step tapered to cast slugs for checking barrel measurements.

[teraph]

Thanks for the advice. The rifle is a J.C. Higgins Model 45 and I have not slugged the barrel yet. Looks like a micrometer is in the chute for the next purchase as well as a thicker dowel rod.