So....cam over ?

[Wolfdog91]

So I've been using a lee challenge press for my entire 8-10yr lil reloading career. Well recently installed my late father in laws RCBS RCll press and started using it and I have to say is the first time I've really experienced this "Cam over" thing . I have it set for just a slight bit but honestly I love it and it really seems the ammo I've been making with it is much more consistent then with my lee. Shoulder bumps,ease of resizing,bullet seating ect all seem much more consistent, at least as good as my measurement skills will allow me to see lol ! Also I'm an over thinker and something about that lil cam over action just really really puts my mind at ease.

Anyhow I was curious what the pros thought when it cam to cam over on a press. Good bad ? Dose it help with consistency? I'm no f class or bench rest guy , just a dude who like trying to make decent ammo
Thanks !

 

[Bill Norris]

My R C press will cam-over with some of my dies but I see no harm at all. As you mentioned seems to produce tighter specs. with the re-sizing.

 

[jackieschmidt]

The only die I do not allow to cam over is my seating die. I let the shell holder stop dead on the bottom of the die, giving accurate seating depth from round to round.

with my sizing dies, (30 BR, 6 PPC), I kept the shell holder contact the die with a little cam over of the linkage.

 

[Bill Norris]

The only die I do not allow to cam over is my seating die. I let the shell holder stop dead on the bottom of the die, giving accurate seating depth from round to round.

with my sizing dies, (30 BR, 6 PPC), I kept the shell holder contact the die with a little cam over of the linkage.

Yea, I don't allow cam-over on my seating dies either.

 

[RegionRat]

There are some things about presses and sizing that are subject to the stiffness of the press. They require a study and trade-off to see if cam-over or hard contact is the right way to go, or if you get away without it.

In the context of having a low stiffness press, and a high dispersion in the sizing force, you owe it to yourself to study the cam-over option. This option takes the press stiffness and size force dispersion out of the equation.

 

[Wolfdog91]

Yea, I don't allow cam-over on my seating dies either.

So is cam over just not consistent enough for seating ?

 

[Chris Edmondson]

I like cam-over with my Forster CoAx, I do think it results in more consistent peak force. That said, it makes it easier to consistently apply an inappropriate amount of force. The die I have in mind is the Lee neck sizing collet die; Lee recommends not camming-over, most likely because it makes it easy to apply too much compressive force which may leave collet marks on the outside of the neck, among other things. It's simple though, to progressively adjust the die's height so that cam-over provides just the right amount force to achieve desired neck tension without trashing the neck. Once it's set, consistency is excellent.

 

[joshb]

Sometimes you need cam over, sometimes you don’t. If you need to push your brass all the way into the die to get the sizing you want, a little cam over is needed. Do a little test to see why. With the Ram all the way up, screw your die in until it touches your shell holder and lock it there. Then put a piece of lubricated brass in and raise the ram to the top and look to see if there’s a gap between the die and the shell holder. Usually, there is a small gap due to a little “flex” in the press linkage. If you have the gap, you need to screw your die in a little more until the gap disappears.
Too much cam over pressure isn’t good for you or your press. Just enough to get rid of the gap.

 

[Bill Norris]

So is cam over just not consistent enough for seating ?

I dont think cam over is needed with seating. I think as Jackie eluded to the solid contact with the shellholder and bottom of the die is good enough when seating bullets.

 

[Coyotefurharvester]

I would be crushing brass if I ever set RCBS standard seating die to touch the shell holder.

 

[mousegunner]

Wouldn't you size too much if the sizer was screwed down to eliminate the gap or is this for seating only.

 

[Kracken McGraw]

Wouldn't you size too much if the sizer was screwed down to eliminate the gap or is this for seating only.

This is where a set of Redding Competition shell holders come in to play.

 

[swd]

Factory dies are anything but precision so I don’t think of cam over or not. I look at how much head space the die sizes my brass. I’m looking for .002” and whatever it takes to get there. Whether or not you anneal also plays into the equation.

 

[RegionRat]

With shell holders shown above, the shoulder datum can be controlled while making hard contact or using cam-over. The solid stack of the die and shell holder does not rely on the stiffness or repeatability of the press linkage. This method requires the least amount of skill to get repeatable results with folks who have low experience with metal working.

 

[WSnyder]

I’ve been using a positive stop press (Redding Ultramag) for 40 years and have never had an issue sizing brass consistently and right where I want it. I suppose it’s all about learning the equipment you have and making it work for you. The only cam over press I have is a Harrell’s for sizing PPC and it works just fine too.

 

[joshb]

Wouldn't you size too much if the sizer was screwed down to eliminate the gap or is this for seating only.

I’m only talking about sizing. The answer is in your die and chamber.

 

[Florida Wally]

I have found that as others have mentioned “cam over” helps when sizing to get consistent shoulder bump. When the press “cams over,” it takes all of the slop out of the linkage as well as any other sources in the setup and exerts a consistent force on the base of the case and up through the shoulder irrespective of the amount of lube used. If the press does not “cam over,” the amount of shoulder bump is dependent on the amount/location of lube used to overcome the slop in the press. I would get inconsistent results when there was a gap between the shell holder and the bottom of the die since there is no positive stop for the case, the stop is dependent on the amount, type and location of the lube. With “cam over” when the shell holder is pressed against the bottom of the die, there is a positive stop between the top of the shell holder and bottom of the die.

I don’t seat bullets on the press since I can’t measure seating pressure like I can when using an arbor press with a gauge. “Cam over” isn’t needed when decapping or using a mandrel, so I only use it while resizing.

 

[DaveTooley]

The title of the next thread.

"Case head separation, what's up?"

 

[sqrlgtr]

Sometimes you need cam over, sometimes you don’t. If you need to push your brass all the way into the die to get the sizing you want, a little cam over is needed. Do a little test to see why. With the Ram all the way up, screw your die in until it touches your shell holder and lock it there. Then put a piece of lubricated brass in and raise the ram to the top and look to see if there’s a gap between the die and the shell holder. Usually, there is a small gap due to a little “flex” in the press linkage. If you have the gap, you need to screw your die in a little more until the gap disappears.
Too much cam over pressure isn’t good for you or your press. Just enough to get rid of the gap.

When I use a Lee collet neck die I set up my Rockchucker to cam over and can tell I get a more consistent seating pressure. I seat with arbor dies and press....

 

[NorCalMikie]

With "cam over" every stroke at the top will be the same. Too much and you CAN damage stuff. Been there, done that.