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March 12, 2009, 11:24 AM | #1 |
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? on Lee Neck Sizing die initial setup
I returned my 2 piece RCBS .243 dies in favor of the Lee 3 piece set with an additional neck sizing die. To neck size only with the RCBS FL, I was to screw the die in until it hit the shell holder and then back it out one turn.
The instructions for the Lee Neck Sizer says to touch the shell holder plus one turn more for Lee presses only. All other presses (I have the Rockchucker Supreme) it says to touch the shell holder and then screw in TWO more full turns to prevent the press from cam over. It says this allows you to "feel" the neck being sized. As a newbie, I'd rather have the press's ram stop on it's own rather than being able to continue to force the neck further up the die if I apply too much pressure. This seems bass-ackwards but I'll do it if that's the recommended way. Just wondering if all Lee owners really do it this way if they don't have a Lee press? Thanks. |
March 12, 2009, 01:08 PM | #2 |
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Doesn't make sense that you'd turn the die two full turns, after contact with the shell holder, in order to PREVENT cam-over. I've used Lee Collet dies on Lee presses, as well as a Rockchucker and my Dillon 650. You can feel the neck's being sized. I had to set my Rockchucker so that it would "cam over" a bit, but you still keep pulling the handle down until it stops.
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March 12, 2009, 01:47 PM | #3 |
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For some strange reason, Lee doesn't like "cam over."
I've reloaded for over 30 years on my RCBS Jr. and found the cam over was just fine, in fact I liked it since I knew that's exactly where the ram was at maximum extension. I bought a Lee Classic Cast about a year ago, and found it has stops built into the linkage to specifically prevent cam over. Don't have a clue as to why. The Lee press works fine and has more leverage than my little RCBS, but for the life of me, I cannot see any advantage in the elimination of cam over. FWIW, I adjust my dies in the Lee press just like I do in the RCBS. I use at least four different die manufacturers sets (Lee, RCBS, Hornady, Redding, etc.) and adjust them all exactly the same way. Never read the Lee die instructions, so it sounds like I'm ahead... Last edited by mkl; March 12, 2009 at 02:02 PM. Reason: Added last paragraph |
March 12, 2009, 05:21 PM | #4 |
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The collet die adjustment is different because of the sleeve that has to be pushed up to close the collet fingers on the neck. The drawback to cam-over is that its mechanical advantages approaches theoretical infinity at the the point the link pivots line up (the dividing line between cam-under and cam-over). That infinite mechanical advantage doesn't let you feel a stop right at that point. You can feel one either before or after you pass it.
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March 12, 2009, 06:22 PM | #5 |
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What, pray tell, is 'Cam over' ?
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March 12, 2009, 09:10 PM | #6 |
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Bottle neck cases are resized using either a full length, neck, or small base sizing die. The die is screwed into a press, with shell holder installed and ram fully raised, until the die base contacts the shell holder. The ram is lowered and the die is screwed in 1/8 to 1/4 more turns. After locking the die in place and raising the ram you should feel a slight resistance when the shell holder contacts the die base and continue pressing until all movement ceases. That is the cam over. It ensures consistent resizing for your cases.
A carbide lined die is adjusted until the die base contacts the shell holder and no farther. Cam over with a carbide die will damage the extremely hard but brittle carbide liner. |
March 15, 2009, 12:45 PM | #7 |
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Thank you for that explaination.
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March 17, 2009, 06:39 PM | #8 |
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You've seen locomotives that turn the wheels on the engine via a large push rod that is connected to the wheel such that the motion of the rod turns the wheel. The point at which the rod is just at fully extended and on its way back is the cam over point. In a reloading press (I have a Redding Ultramag) it is the same situation and the force is maximum at the point just before "returning" as the throw goes beyond maximum. I use Lee Collet Neck Sizing dies and really like the cam over feature as it allows consistent tension. You can use a bullet to determine if you are using enough pressure during sizing. Just turn it in a little at a time and check your bullet fit each time you exercise the ram. The bullet will slip freely into the case until it is sized down to prevent it from doing so. It's not difficult to do. As long as the bullet is not slipping into the case you have neck tension. If you start to go too far you will see marks in the brass from the collet tension. Back off a little if you see the marks.
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