Press flex

[kilotanker22]

I have used a RCBS Rock Chucker for years. I have never had a problem with inconsistently sized cases. It has been excellent really. So Recently I decided to buy a Lee Challenger aluminum press. I found it new in the box although it is over a decade old.

What I have found over the last couple of months is that obviously the aluminum press flexes a lot more than my cast iron Rock Chucker. When my full length die is set on the Rock Chucker, shoulder set back is very consistent. Showing less than .001" difference in shoulder set back through a run of 50 cases. I did this test multiple times with once fired cases as well as cases that have been fired and sized several times. I also performed this test with the Lee Classic Press. With the Lee press, I see an extreme spread of .002-.004" through a run of 50 cases. Quite often I have to run a case through the die several times to get the right set back when using the Lee press.

Just an observation I figured I would share.

 

[Bart B.]

"Soft" presses can produce uniform case headspace if the ram is kept topped out for 5 to 10 seconds. That lets the press spring back set case shoulders the last couple thousandths more.

The lubricity of the case lubes needs to be good and evenly spread on the case. The most slippery case lubes I've used is a 50/50 mix of STP engine oil treatment and Hoppe's No. 9 bore cleaner. A half teaspoon of it in a foam lined tumbler will handle several dozen cases while you're sizing the same number previously lubed.

Goes fast using an RCBS Rockchucker with my left hand holding a lubed unsized case while removing the sized case from the shellholder then putting the unsized lubed case in. Operate the press to size the case with no extra ram dwell time topped out while putting the sized case in one box then grabbing a unsized lubed case from another box.

 

[Unclenick]

Cast iron can have as much as 3¼ times the modulus of elasticity that cast aluminum has. In other words, it will stretch that many times less if the two castings are made from the same pattern. Obviously, a small casting in iron may stretch as much as a heavy casting in aluminum, but that's not apples-to-apples.

Letting the press settle as Bart described is how I've always got tight cases down to size. If your press is rugged, you can also smack it (not too hard) with a deadblow hammer while the case is in the die to help everything find final position. Harbor Freight's smallest shot-filled plastic deadblow hammer works fine.

 

[kilotanker22]

I will try Bart's suggestion. I plan on buying a nicer press inn the near future anyway, even though I already have a Rock Chucker and the Lee Classic.

 

[Bart B.]

I doubt there's a better single stage press than the RCBS Rockchucker. Two or three probably equal it.

Use the Rockcrusher for case resizing and the Lee for bullet seating.

 

[mehavey]

You can also release the ram/pressure a smidgen, then "bump" the case back up into the die.
I find that works a "smidgen & a tad" better that just sitting at the top of the stroke.
(Besides, it give me something to do than just count my fingers)


Test it out and chose whatever actually works for you.
(whatta concept )

 

[buckey]

All great info! but one last thought is that I use Imperial sizing lube and when applied the same from one case to another is does make a difference on the sized casing coming out of the press and with the ram all the way up I hesitate for a second before letting the ram down. When reloading consistency is the name of the game.

 

[kilotanker22]

I bounce back and forth between imperial case wax and Hornady one shot.