Terminology regarding cam-over and die installation

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Doc7

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Hello all,

Getting excited as I plan to finish my reloading bench construction this Friday and begin my first reloads, for my 7mm-08.

I have a question regarding die installation. Many of the instruction manuals state to run the press to the top and screw in the die for contact, and then lower and screw in another small amount.

When they say "the top of its stroke" do they mean, "The Highest Point the Shell Holder Reaches" or "The point when the Handle stops moving down" ? These are not the same, correct? The shell holder goes up and then drops back down slightly in the full handle stroke? Which one is the top with regards to these instructions?
 
This is how I did it - not sure if it's the right way per the details of your question.

I lowered the press handle (raised the ram) and let gravity keep it there. So per your question that would result in the *slight* ram drop. I then lowered the die to just kiss the shell plate. Raised the handle (lowered the ram) and turned the die another quarter turn.

Then the result is lowering the handle using gravity only will not enable the ram to go to fully up - because the die is now stopping furthest upward movement of the ram. And fully sizing a case requires pushing down on the handle - which is when the cam over occurs.
 
Doc7 said:
Hello all,

Getting excited as I plan to finish my reloading bench construction this Friday and begin my first reloads, for my 7mm-08.

I have a question regarding die installation. Many of the instruction manuals state to run the press to the top and screw in the die for contact, and then lower and screw in another small amount.

When they say "the top of its stroke" do they mean, "The Highest Point the Shell Holder Reaches" or "The point when the Handle stops moving down" ? These are not the same, correct? This is basically the same thing, when the press handle stops moving the shell holder should be at its highest point. The shell holder goes up and then drops back down slightly in the full handle stroke? Shell holder shouldn't drop down at all, might a little due to slop in press but should be insignificant. Which one is the top with regards to these instructions? Handle all the way down is all the top you can get.
Click to expand...

See red text in your above quoted message for answers.

Basically you screw the die down until touching the shell holder then a 1/4 turn or so more so the press ram cams over taking all the slight sloop out of the ram assembly. Now this is only for full length resizing, you will get better brass life if you don't full length resize and only bump or move the shoulder back .001" to .005". This can be done with the full length resizing die by only screwing the die most of the way into the press, sizing a case then measuring it with a head space gauge or trying the case in your rifles action.
 
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Some rams cam over some don't. You adj the die when the ram is at the highest point. The harder the brass is more force and travel will be required to size. Different lubes can also change your settings too. Annealed brass will have the least spring back vs 1+ fired brass. Since you only want to push the shoulder back 0.001"-0.002" for a bolt gun its best to keep all the brass in the same state as your die setting will change.
 
To me the whole cam over concept is kind of confusing. In setting a full length resize operation, I generally follow the advice of die meets ram at highest point and then add a 1/8th or 1/4 turn. As a result I get what I would call "dead travel" in the press handle at the bottom of the stroke since there are no mechanical ellipticals or "cams" present. Maybe "cam over" and "dead travel" are in concept the same thing? In reality, aren't we are just taking up slack in the linkage?

At the end of the day, I think the point here is to ensure that there is no slop and sizing is consistent between cases.

.40
 
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Due to manufacturing tolerance and various manufacturers equipment being mixed and paired, I don’t just screw things down and go.

You might get lucky and everything is right but I don’t ever seem to be that lucky.

It would work for a straight walled round just fine but might not be optimal for 7-08 or any other bottleneck case.

“Cam over” is generally used when a linkage goes over center or as the handle is lowered the ram moves up to a certain point then begins to go down.
 
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