Reloading press: "Camming Over"?

[klewan]

I kept seeing the phrase "camming over" in Germz's thread about "What am I doing wrong?". I'm visualizing the press ram reaching the top of its stroke and there is still some travel left on the down stroke of the lever. So as you move the lever to the end of its travel, the ram actually lowers a bit from maximum height. Is this how it works? If it is, why would you want that? I have Lee presses, all of them have a lever stop and that's as far as it will go.

[BigBronco]

Camover is the method do assuring full die engagement. This technique is not, repeat not for use with carbide dies. It us mostly used with steel rifle dies. Camover can cause carbides to crack.

[buffybuster]

Lee presses do not cam over.

[rsrocket1]

There is no need to adjust a die so that it works in the "camover" region of the a press that does so. Just screw it down so that it fully engages well before the camover position. Then push down on the handle until it stops. Be sure that with a sizing die, the die touches the shell holder.

The danger of camover is that it works like a vice grip and you just don't know how much excess force you are putting on the die. A steel die will bend, a hardened die may crack.

[knucklehead0202]

or you smoosh ammo/brass in a rockchucker.

[GeoffLinder]

Cam-over may, or may not be required to get proper shoulder bump. Only a measurement of actual bump amount in a gauge will tell you if this is needed.

You do not have to actually cam-over a press to get this effect, it really means to adjust the die down enough to apply more force than just simple contact between the die base and the shell holder. Some presses will actually run past the max contact point and release a little tension, some will just reach a max tension point.

As noted in 2nd response here, NEVER use cam-over with a carbide die as it will crack because carbide is brittle whereas plain steel dies are somewhat ductile and can handle this.

[ar15barrels]

There is no need to adjust a die so that it works in the "camover" region of the a press that does so.

The advantage of camming the press over every cycle is that you eliminate the variable of press frame stretch and brass hardness.

By using redding competition shellholders, you can get much more consistent shoulder datum lengths.

If you are NOT using spacers between the die and the shellholder or some similar method to the redding shellholders, then you are letting the brass hardness and the press frame stretch determine your shoulder length instead of using a positive steel-on-steel stop that camming the press over allows.

[klewan]

The advantage of camming the press over every cycle is that you eliminate the variable of press frame stretch and brass hardness.

By using redding competition shellholders, you can get much more consistent shoulder datum lengths.

If you are NOT using spacers between the die and the shellholder or some similar method to the redding shellholders, then you are letting the brass hardness and the press frame stretch determine your shoulder length instead of using a positive steel-on-steel stop that camming the press over allows.

The Lee die instructions say to run the ram all the way up, screw the die down into contact with the shellholder, lower the ram and turn the die in a further 1/4 or 1/3 turns and lock it in place. This is done to compensate for frame stretching and any other slop.

I'm still not clear as to whether the ram is actually going past top dead center and descending as you continue the lever movement. Lee has a lever stop; you're not going past that. But it sounds like other presses don't, that if you put a dial indicator on the shellholder and cycled the press, it would show the needle spinning in one direction and then reverse as the press went past TDC. Is that true?

[Spyder]

I run an RCBS turret press. There is JUST enough give in the turret, that if I don't cam over, then my .308 brass will not chamber in some of my .308 firearms because the shoulder is not bumped back enough.

I'm unfamiliar with other presses, but on mine, it does not descend at all, it gives it that extra bit of solid positive engagement that takes out any slack in the system and ensures consistency. And I'm sure I used all the wrong terms, but it makes sense to me.

[wxl]

If you don't cam over when you set up, you will see a small gap between the shell holder and the die when you resize due to the stretching. The brass in the small gap is not getting resized. This may or may not cause a problem depending on your chamber.

[mark501w]

If you set it right you won't feel the "camming over" during the sizing process.

[Coyotegunner]

Certain dies I have to cam over hard.Usually I have kept notes on which ones.Rockchucker used.
Examples:My Sako 30-06 Finnlight,the brass has to be resized with a heavy cam over.Right at 1/2 or more of a turn on the die past seating against the shell holder.I check the brass after the first one to make sure it closes in the chamber.Yes it is accurate,with the tight*ss chamber.
I have a 204 Ruger in a Howa.It has almost zero cam over.It is almost zero turn down past contacting the shell holder.Sloppy chamber??Well it is accurate anyway.If I turn it like the 30-06 it crushes the brass,by the way.
I say experiment with the amount of cam over,checking the brass in you chamber.Be sure to trim it.
Sorry that is all part of making your own custom ammo.Part of the fun also.
Most reload die instructions tell you to go 1/2 turn past contact with the shell holder,with the press handle down.You did read the instructions didn't you?Like others have noted.Their equipment is different for other dies.

[ar15barrels]

I'm still not clear as to whether the ram is actually going past top dead center and descending as you continue the lever movement. Lee has a lever stop; you're not going past that. But it sounds like other presses don't, that if you put a dial indicator on the shellholder and cycled the press, it would show the needle spinning in one direction and then reverse as the press went past TDC. Is that true?

It really does not matter if you cam-over or not, but when you do, it is positive proof that you reached the maximum travel of the ram.
I much prefer my rickchucker where I can feel it pop over to my lee classic cast where I don't feel it pop over.
I actually ended up selling the lee press so I don't worry about that anymore.
All my other presses go just barely past so you can feel them pop over just as they reach their linkage stops.

[gunboat]

Two reasons for "cam over". Well three if you count "we always done er thata way"
One -- as randal pointed out it gives a mechanical feel to reaching the top of the stroke --
two -- the handle on older press's did not always naturally stay at the top of the stroke when not cammed over so when you were fumbling for a primer to put in the primer arm the bugger would drop and invariably strike you in a most tender spot.
my ha-penny

[mark501w]

One of the many dangers of reloading!