Cam over?

[Rich Coyle]

There is a thread going talking about "cam over". Apparently I don't know what cam over is. Perhaps someone with more knowledge than me could chime in.

 

[jimbires]

cam over is when the shellholder makes solid contact with the die , you feel the contact but keep pushing then you feel the press kind of go over center , " cam over " .

you will get cam over by adjusting the die to make contact with the shellholder when it's raised all the way up , then lower the shellholder and give the die a quarter turn down . when you raise the shellholder again go the whole way , you will feel the press cam over .

 

[Rich Coyle]

I see. I don't think I ever did the cam over.

I am a fussy loader and check a fired case for head space. Then I start full length sizing too long and slowly get to the same headspace with a sized case. The reason I think I am fussy is I check every case for correct headspace as I size it. I set anything more than .002" to the side and use that for fouling after cleaning. In fact that's when I use primers that have fallen on the floor. I don't use them in my "good" loads.

 

[Citius7]

So what are the negatives?

 

[bigedp51]

I'm still using the RCBS Rockchucker press I bought in 1973 and it now has a little slop in the linkage. And when the press cams over with the die making hard contact with the shell holder the all the slop is eliminated.

I use Redding competition shell holders to control shoulder bump and remove any slop in the press. And if the die doesn't make hard contact with the shell holder you can have shoulder bump variations.

Bottom line, cam over eliminates the press from any sizing variations. In the past I would use feeler gauges to adjust shoulder bump like in the photo below. But when I started using the competition shell holders my shoulder location after sizing is now more constant.

So remember over time the pivot pins in the press linkage will wear and create slop. And when the die and shell holder make hard contact the press is eliminated from sizing variations.

 

[Lonewolf74]

I thought you wanted your sizing die to cam over and make firm contact with the shell holder to take up slack and account for press flex to make your cases as identical as possible?

I know this sometimes bumps the shoulder back farther than wanted which is why Redding has the competition shell holder's. I've played around before with setting the die off the shell holder to control shoulder bump but I would experience .006 variance within my lot of cases that way. With the cam over method it's never more than .002 so I opted to go that route for consistency even if I'm bumping the shoulder back more than I really want.

 

[jimbires]

I agree 100% with big Ed . what he is saying , is what I have found to be true .

 

[bigedp51]

I agree 100% with big Ed . what he is saying , is what I have found to be true .

jimbires, you must be almost as smart, good looking and modest as I am.

I would like to think that the die manufactures tell you for die setup and the reason Redding made the competition shell holders has a reason.

I buy a lot of bulk once fired Lake City brass in 5.56 and 7.62 and use the Redding shell holders. I also pause and count to 4 at the top of the ram stroke to help reduce brass spring back with this once fired brass.

My RCBS Rockchucker press is 44 years old and two nights ago I was sizing 500 once fired military Winchester 9mm cases and the pivot pin at the bottom of the ram fell out. I pounded the pin back in and staked the pin and I'm good for another 44 years.

Bottom line, when you reach camover with hard contact between the die and shell holder it doesn't matter how old the press is. Now think about how much flex and slop there is in progressive or turret presses. Flex in a press when sizing handgun ammo is no big deal but shoulder location on rifle cases is a different matter.

 

[Edd]

I'm still using the RCBS Rockchucker press I bought in 1973 and it now has a little slop in the linkage. And when the press cams over with the die making hard contact with the shell holder the all the slop is eliminated.

I use Redding competition shell holders to control shoulder bump and remove any slop in the press. And if the die doesn't make hard contact with the shell holder you can have shoulder bump variations.

Bottom line, cam over eliminates the press from any sizing variations. In the past I would use feeler gauges to adjust shoulder bump like in the photo below. But when I started using the competition shell holders my shoulder location after sizing is now more constant.

So remember over time the pivot pins in the press linkage will wear and create slop. And when the die and shell holder make hard contact the press is eliminated from sizing variations.

I use feeler gauges like in your picture then when I determine the correct thickness I use a round shim on top of the shell holder.

 

[jrock]

I agree that using cam over provides consistency. My most notable experience was with the Lee neck sizing collet dies. They say not to cam over in the instructions and just use 20 or so lbs of pull. I couldn't get that consistent so after a few tries, I just set the press so it would cam over with the slightest force and guess what? Consistent neck sizes.

 

[Rich Coyle]

I agree that using cam over provides consistency. My most notable experience was with the Lee neck sizing collet dies. They say not to cam over in the instructions and just use 20 or so lbs of pull. I couldn't get that consistent so after a few tries, I just set the press so it would cam over with the slightest force and guess what? Consistent neck sizes.

Exactly.

 

[Citius7]

I agree that using cam over provides consistency. My most notable experience was with the Lee neck sizing collet dies. They say not to cam over in the instructions and just use 20 or so lbs of pull. I couldn't get that consistent so after a few tries, I just set the press so it would cam over with the slightest force and guess what? Consistent neck sizes.

Concur.