Did some reloading yesterday for a friend's new M673. I've loaded for my M600 and 700 Classic for about 10 years with no problems, this using RCBS dies and several different bullets.

Using a new set of Lee dies after seating some 225 gr. Nosler Partition and 225 Sierra bullets it was noted that the bullet could be pushed back into the case. There was no problem with the 160 gr. Hornady pistol bullet for the small game load or the 220 grain Speer FP.

After doing some measuring the following was found:

Expander ball on Lee die: .356

Expander ball on RCBS die .355

Speer 220 .358

Nosler 225 Pet. .3565

Sierra 225 BT .3565

Hawk 250 .358

Hornady 180 SSP .357

Remington 250 .357

Barns 180 & 200 .357

Hornady 160 CL-SIL .356

Hornady 180 CL-SIL .356

The expander ball on the Lee die was polished down to .354 and now everything is good and tight.

One question I have to all you is how much smaller should the expander ball be than the bullet to be loaded?

Thanks,

Bob

After speaking with the Nosler and Sierra Tec. people and doing a lot more measuring with a micrometer the problem seems not to be bullet diameter as the closer diameter is .3572-5" for both the Sierra and the Nosler.

The problem comes from the fact that just above the base of the bullet where the diameter is greatest the bullet starts to taper ever so slightly...but by the time one has seated the bullet to 2.800 loa one has expanded the neck with the base of the bullet and the part of the bullet that is actually in contact with the neck is .0002-.0005 smaller. Just enough to cause slippage problems especially if ones expander ball is somewhat over spec.

Barns, Hornady, Speer and Remington bullets are all the same diameter from the base to the where the bullet starts to taper to the point.

The Hawk Bullets measure .359 at the base, .3585 just ahead of the base and .358 in the area that is going to be in contact with the neck....I've never loaded any of these and probably won't.

Any ideas on how to put a "taper crimp" on the neck of this round would be appreciated. Lee will make a custom Factory Crimp die for $25.00...maybe that would be the way to go for these two bullets just lightly cripming them in place along with the smaller diameter expanding ball.

Bob

Might also look at customizing a 357 mag seater die to get the crimp you want. - Dan

I would not worry about all those details...You can take .003 to .004 off any expander ball...your only concern is will the bullet seat and not crush the case neck....

On a big bore DGR, I turn the expander button down 3 or 4 thousands, use a powder that will meet the base to the bullet and by doing this I do not have to crimp....

The difference in bullets for a particular caliber are so close that it is irrelavant in the tightness of a case, but whatever the bullet size the release will be the same...No need to chase your tail with twaddle.

I would not worry about all those details...You can take .003 to .004 off any expander ball...your only concern is will the bullet seat and not crush the case neck....

On a big bore DGR, I turn the expander button down 3 thousands to start with and thats usually enough. I use a powder that will meet the base to the bullet and by doing this I do not have to crimp, but in a 458 Lott and up I will add a very very light crimp....

The difference in bullets for a particular caliber are so close that it is irrelavant as to the tightness of the case, but whatever the bullet size the release will be the same...No need to chase your tail with twaddle.