maximum cast bullets downsizing

[danyboy]

Is there a limit to as much downsizing one can do on cast bullets ? Can I downsize a .329 bullet down to .326 ? How far down could I go ?
Danyboy

[runfiverun]

depends on your press,your arm strength and the lube you use and if you want smooth sided boolits or lube grooves left.
but 329 down to 326 no problem at all,you might have some growth after sizing though.

[JeffinNZ]

I think increments is the answer. If you are going to size down a lot then perhaps 2-3 thou at the time is the way to go. .329 - .326 - .323 - .319 etc.

There will come a point however where you end up with a smooth sided bar of lead. :shock:

[BABore]

It also depends on the direction and method. I size down 0.461 diameter WD boolit to 0.452 using a push through die in my Rock Chucker in one shot. I sprayed down the boolits with an alcohol/liquid lanolin case lube I made. StarMetal sizes down 7mm boolits for his 6.5. Base first in a normal lubrisizer is alot more work and could bend skinny boolits. Acouple 3-5 thousandths is nothing.

[danyboy]

Very helpful guys. I apreciate the help. I tried to chamber Lee mold .329 cast bullets in my Berthier with Graf brass but couldn't chamber it.
Thanks,
Danyboy

[jonk]

Dany,

That isn't surprising considering the sizing dies size the case for a .323 bullet. What you need to do is get an expander for the .329 bullet from a set of 8X56R dies. Then see if that will chamber. Better plan yet, fireform one of the cases and see if the .329 bullet will fit in the fired case. No waste of buying things that way. If it doesn't you could try neck turning the brass to free up a few thousandths of an inch of space. But you should slug your bore anyhow; my 2 Lebel Berthiers measure around .326 so you could size down to 1/1000 over bore diameter and see how that goes.

Sizing a 329 down is nothing. Before Lee made that mold I regularly sized down 338 slugs to .329 (jacketed) and sizing jacketed bullets is HARD.

[danyboy]

I slugged my bore: bore=.315, groove=.3253. Will fireform somehow with cream of wheat and cornmeal as suggested yesterday by jonk in a different topic and will do my homework. Unbelievable how helpful this forum is. Will get back to you.
Danyboy

[BABore]

Any new or once fired case that was fired in the gun that was a full powered load will work. What your looking for is chamber neck diameter. The case will expand to seal the chamber, and then spring back a couple thousandths. A boolit that will just slip fit into this fired case will be the largest diameter that you can safely use. You have to leave enough neck clearance for expansion and boolit release without spiking pressure. Using a boolit this large will keep it from yawing when kicked in the pants and is one of the three boolit fitting points that contribute to accuracy with cast. The other two are throat fit and bore engraving. If they are all achieved, the boolit can only go straight. The bbl becomes the sizing die. Things can get tricky when you find out the throat is considerably larger in diameter than what the chamber neck clearance will allow. Now you have to play games with brass thickness and neck turning.

Getting a larger than normal boolit to fit the case typically requires a different expander so you end up with 0.002 to 0.004" of case neck tension. A Lee universal flaring die, or similar, is also useful to bell the case mouth so you don't shave lead.

[danyboy]

I did a chamber cast with graphite: chamber neck O.D. is .353 and graf brass is .010".
Danyboy