Thread: Lee or RCBS?
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Old November 18, 2012, 08:55 AM   #19
Bart B.
Senior Member
Join Date: February 15, 2009
Posts: 6,318
A friend years ago made some tests with different "O" frame single stage presses. He wanted to know how much "spring" the press had for a given force applied to the die thread location at the top. He had several makes and models including Lyman, Lee, RCBS, Pacific, Hornady, and others I now forget.

The old, big, RCBS A2 sprung the least for a given amount of force on it. And the RCBS Rockchucker sprung the least of all presses of that size. Smaller ones sprung the most. On average, the "C" type presses sprung the most.

He measured them by mounting them upside down and held by the toggle pin at the bottom then hanging a 150 pound weight on a 7/8-14 thread bolt screwed into the die. The dimension change between the pin and bolt was measured with a dial indicator.

What does this mean?

When full length sizing fired bottleneck cases, the press that springs the least will typically end up making the head-to-shoulder distance (case headspace) spread the least. This helps make reloaded ammo more accurate and cases last longer.

One thing I've noticed is the presses made today have a lot more slop in their ram in its guide. My two Rockchuckers bought in 1979 had a .001" play in the ram at its full height when new. Now they've both got about .002" after reloading thousands of rounds of ammo. My RCBS Jr. bought in 1966 had .003" play when new, but now it has about .010" after a few thousand rounds reloaded. In checking the play in several brands and models, including the Rockchucker, they've all got enough to easily be seen; no dial indicator needed. That's several thousandths slop.

I'd try to find a medium duty/size press with no visible slop in the ram at full height. Then completely disassemble it then clean it once in a while and keep it lubricated (STP engine oil treatment's a great high pressure lube) to reduce (eliminate?) wear.
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