Cam Over OR Not.

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Sometimes I have to cam over just to bump the shoulders back far enough. Other times, I'm just barely from touching the shell holder and they chamber great.

You definitely don't want to have too much headspace or you get too much stretch.

Just my .02.


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I had RCBS presses for years that cammed over. They worked great. I bought a Lee Classic Turret to load pistol on and it doesn't cam over. It works great. I can't tell any difference in the ammo. I liked the spent primer collection and Safety Prime so well I sold the "Chucker and bought a Lee Classic Cast too. There isn't any thing wrong with a Chucker, I just liked the Lee better.
 
On my bolt action, I actually have a resizing die that is set based on chambering the case after each incremental adjustment until it chambers with only slight (very slight) resistance. When I started with my 1970's vintage Rockchucker many years ago, all instructions specified to cam-over when setting up the sizing die.
 
Never really gave it much thought.

In reality, if you don't want the final little bit of sizing or whatever when the press cams over, bump the dies up a touch.

I figure the way my dies are set has more to do with how much they size the case than if the handle cams over or not.
 
I adjust my sizing die to bump the shoulder. With the combonations of different dies, chambers and cases my press sometimes cams over and sometimes it does not. Following the instructions that come with the dies, most suggest cam over. If you do this your ammo should work in any firearm but may suffer from shorter case life.
 
As a long time reloader and pdog shooter, I shoot a lot of rifle rounds a year. I adjust all of my dies to bump the shoulder back so that the case just fits the chamber of that rifle. I use a set of dedicated dies per rifle even if I have multiple rifles in one caliber. Take a fired round and adjust your sizer down until the case just fits well in that rifle without a bullet in it. This will eliminate any headspace issues as well as make your cases last longer due to stretch and overworking the brass. I advise people not to follow the RCBS instructions of cam over. If you have a rifle that has excessive headspace, this will cause your brass to separate sooner than my way due to making it too small for the chamber, it will stretch too much each time it is fired and you will get fewer loadings per brass life.
 
Some presses require it some don't. If the press is design to cam over you must do it to get consistency. If you don't you will be all over the place when it comes to any function.
 
I read the article too and agree that cam over only flexes the press and adds somewhat to wear on the press. Firm contact is all that's needed or remove material from the bottom of the die if your die doesn't push shoulders back enough. A fine adjustment from firm contact to cam over though.
 
Except for .25 ACP, all of my pistol caliber dies are carbide dies from Lee. All of my rifle caliber dies are from RCBS and are not carbide. The instructions that came with the Lee dies says to set them up so that the press comes to the top of the stroke but does not cam over. The instructions that came with my RCBS dies all have setup instructions that cause the press to cam over.

My .45 ACP die was is one of the old Lee "Speed Die" which incorporated all the functions into a single die. The instructions for it - but not appearing in any of my Lee 3 die sets - specifically says to make sure the press does not cam over because the shock of the press cam over could shatter the carbide insert.

So, I think the bottom line is that unless you know what you're doing well enough to ignore them - and accept the liability for doing so - you should follow the manufacturer's instructions.
 
Me just thinking out loud...

When a manufacturer makes presses that cam over, their die instructions are to cam over.

When a manufacturer makes presses that don't cam over, their die instructions are not to cam over.

So far, I'm not shocked. It's what I expect.



So, have any of you personally actually had a press, a die, a shellholder, or any part
actually break (catastrophic failure) from cam-over or not-cam-over? Not stories like
"Well I heard of a guy who's cousin says he had a friend who worked with a guy who thinks maybe..."
I'm wondering about you and me personally, have we experienced catastrophic cam-over failure?


Or perhaps this is just each manufacturer issuing its own die instructions because that's how it makes its presses?


Not being confrontational with anyone. Just wondering.
 
I have to use a hard cam over when loading for my .243. I've been doing that for several years now. Thousands of rounds as my daughter uses it to hunt and shoot matches with. I've never had anything break on my press


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ants said:
Me just thinking out loud...

When a manufacturer makes presses that cam over, their die instructions are to cam over.

When a manufacturer makes presses that don't cam over, their die instructions are not to cam over.

So far, I'm not shocked. It's what I expect.



So, have any of you personally actually had a press, a die, a shellholder, or any part
actually break (catastrophic failure) from cam-over or not-cam-over? Not stories like
"Well I heard of a guy who's cousin says he had a friend who worked with a guy who thinks maybe..."
I'm wondering about you and me personally, have we experienced catastrophic cam-over failure?


Or perhaps this is just each manufacturer issuing its own die instructions because that's how it makes its presses?


Not being confrontational with anyone. Just wondering.
Click to expand...
The instructions on RCBS's website for its dies:

http://www.rcbs.com/RCBS/media/RCBSMedia/PDFs/Instructions/English (EN)/ReloadingDieInstructions.pdf

Includes specific instructions warning users to not let the press cam over when using carbide dies and in a black box specifically attributes this to the shock of the cam over possibly damaging the carbide.

And while I have not personally destroyed any carbide dies by allowing them to be shocked a the cam over, I have seen photographs posted on various sites showing shattered and dislodged carbide sizer rings. I will acknowledge that's not causality as such failure could be attributed to a manufacturing defect, but when the manufacturer says don't allow the press to cam over because it could happen, I've got to believe they've got experience with it happening so I'm not going to demand third party confirmation.
 
I did not read the article but I'll give my $.02 anyways . I think the most important thing in this is the term "CAM" over . A press that cams over is just insuring your die and shell holder make hard contact . The camming action is forcing hard contact between the two . You can adjust any die to not cam over in a cam over press and still make hard or light contact . You just screw the die down more . It will then be up to you and what you feel to insure you size the case properly .

Now my understanding and experience of why you want can over or hard contact between die and shell holder . Some presses have more flex/deflection in the linkage or press it self then others that results in inconsistent "case head space" ( length from head to datum point on the shoulder)

Case in point is the Hornady LnL classic single stage press . IMHO this press has a lot of flex/deflection compared to others . Depending on the size and how work hardened a case is you can get as much as a .006 swing in "case head space" if the die and shell holder do not make hard contact .

These pictures show what I mean . This is two pictures showing the Hornady single stage press and how much deflection it can have when sizing a 308 case .

First pic is the ram fully up and the die screwed down to just kiss the shell holder .
SN05Kz.jpg

This second pic shows how much stretch/flex/deflection the press has when sizing the 308 case with the die locked in place as shown above .

h3j3Nj.jpg

That shows how one can get very inconsistently sized cases . It also can explain how if you have a chamber that needs you to FL size a case and you set the die to touch the shell holder but when you size the case it does not bump the shoulders back enough . It is do to the press deflection .

Now when sizing for a specific chamber size and or just bumping the shoulder back .002 or so . Many don't even need the die and shell holder to touch . This is true in my case and resulted in very inconsistent "case head space" do to how much my press would deflect/stretch .

What I ended up doing was using a feeler gauge under the case head between the head and shell holder to raise the case up a tad to bump the shoulders a little more when needed .

k441.jpg

To clarify I did not need to do this on every case . Most would be sized to what I wanted but there were some that fought the resizing . Those cases would not have there shoulders bumped back as much as the others . On those cases I'd lift them up in the shell holder and resize them again resulting in the shoulders being bumped back the extra amount the feeler gauge raised them .

I used this method for quite a while which resulted in me needing to measure every single case after sizing . It was very time consuming to get all my cases sized perfectly or shoulders bumped .002 .

Then I was introduced to the most beautiful product . That is the Redding competition shell holders :neener: . It was all peaches and cream after that . These shell holders are designed to remove all press deflection/flex while still controlling the size of your "case head space" . Each shell holder ( set of 5) is .002 taller then the last resulting in you being able to size a case .010 longer while still making hard contact then you can with a standard shell holder .

Since then I now can size a few cases to get the right shell holder . Once I have the right one for the sized case I want . I no longer need to measure every case to insure it was bumped back correctly . They all come out VERY consistent . The time I save and the consistency I get makes the Redding competition shell holders well worth the cost . http://ads.midwayusa.com/product/52...set-1-308-winchester-30-06-springfield-45-acp

They also help when loading for different rifles with different chamber sizes . Instead of adjusting the die for each rifle . You just swap out the shell holder .

Redding through Midway USA said:
The Redding Competition Shellholder Kit #1 consists of five shellholders in varying heights with increments of .002". Allows you to increase or decrease the case to chamber headspace without adjusting the dies.
Click to expand...

AS for carbide dies . They are almost always for non-shouldered cases which a little press deflection is not going to effect the end result .
 
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jwrowland77 said:
Sometimes I have to cam over just to bump the shoulders back far enough. Other times, I'm just barely from touching the shell holder and they chamber great.

You definitely don't want to have too much headspace or you get too much stretch.

Just my .02.


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Click to expand...
I am with JW on this one. It depends on the individual rifle chamber. I have had rifles with a minimum headspace that would not chamber a round without camming over. My old Ruger 270 wanted the die just touching the shell holder. They all are different.
 
I have cam over presses, I have non cam over presses. I have press instructions from RCBS that comer cam over presses; I also have instructions from RCBS that cover non cam over presses. I have 5 Rock Chucker presses, none of my Rock Chucker presses cam over.

2 of my Rock Chuckers are attacked to Piggy Back 11 attachments. The Piggy Back 1 & 2 is auto advance meaning; to everyone else that means nothing but to me it means if my Rock Chuckers cammed over the auto advance mechanism would reverse.

Reversing the auto advance mechanism would render the one way clutch scrap or it would lock up the press.

Then it comes to bump; all of my cam over presses are bump presses. None of my non cam over presses are bump presses because they are not designed to reach the top of the stroke and then reverse directions. When adjusting a die in a cam over press the die is adjusted to the shell holder after the ram reaches the top and starts down. Meaning the ram bumps the bottom of the die at the top before cam over. A reloader with a feeler gage can measure the amount of bump if he zeros the shell holder to the die at the top of the stroke then measure the gap after cam over. A dial indicator or depth gage can also be used.

Die instructions suggest the additional ¼ turn after contact when the ram is up, for a non cam over press that would be .017”+; and no one ask “What is that about?” The additional ¼ turn of the die increases the presses ability to overcome the cases ability to resistance sizing.

I do not insist of full length sizing therefore I do not find it necessary for the die to contact the shell holder when the ram is up during sizing; but when I adjust the die to the shell holder with an additional ¼ turn after contact I check to see to see if the die contacts the shell holder. If the case is holding the shell holder off and there is a gap between the shell holder and bottom of the die the case did not get full length sized. Not a dilemma but consider an additional ¼ turn. That would lower the die ½ turn or .035+”.

I find it much easier to size a case to fit the chamber than size a case to fit a chamber I do not have.

F. Guffey
 
I don't understand the need of a press to go over top dead center and a bit down for any sizing. If one doesn't get the results from a press that will travel all the way up and stop, why not just adjust the dies to accommodate the "slop", wear and tear on the linkage, etc.? I can't see any advantage for a ram to travel up then go back down a bit...
 
I don't understand the need of a press to go over top dead center and a bit down for any sizing. If one doesn't get the results from a press that will travel all the way up and stop, why not just adjust the dies to accommodate the "slop", wear and tear on the linkage, etc.? I can't see any advantage for a ram to travel up then go back down a bit...
Click to expand...

I have 12 Herter presses, all of my Herters are cam over presses. When I adjust a die in one of my Herter presses I raise the ram until it cams over; after it cams over I adjust the die to the shell holder. To lower the ram the ram must travel up before I can lower it.

The A2 RCBS press is also a cam over press. The fact it cams over makes it a bump press. The bump press bumps twice, it bumps once on the way up and again on the way down. No one measures the amount of cam over, if they did they could determine the effect bump has on the presses ability to overcome a cases ability to resist sizing. When a die is given an addition ¼ turn after contact on a bump press the .017”+must be added to the amount of cam over.

I was asked to help a friend, I had no clue what he got involved with but he had to brace himself with one leg against the bench and pull the handle with both hands to lower the ram on his RCBS A2 press. I had him to raise the ram again, I measured the gap between the top of the shell holder and die; the gap was .017”. Again, the .017” had to be added to the amount of cam over.

Before I left for his shop he instructed me not to bring my no-name case lube because there is nothing outside of Imperial and Dillon in a can or bottle that will be used in his shop. You have no ideal much effort is required to make that stuff look good.

F. Guffey
 
I can't see any advantage for a ram to travel up then go back down a bit...
Click to expand...

I'm not sure that's the reason for cam over , it's just what happens . I'd think the caming is where you have the most leverage in the linkage and stroke . I find it easier to cam over because I know I've completed the stroke with the correct amount of force . I blew the cap off my 308 collet die because I put to much force into it . Everything can be a learned feel but sometimes you learn the hard way .

I also go back to my previous post and believe presses that are designed to cam over . Have directions to do so to remove the linkage/press stretch/deflection . I believe these manufactures know there is a lot of give in the system and cam over removes this slop .
 
As far as I am concerned, this is mostly much ado about nothing. For the most part, we are simply talking about properly adjusting dies in a press, and anyone can screw that up if they want to - especially if they either refuse to follow directions or cannot understand the concept. And the evidence leads me to suspect the author of that article does not know near as much as he thinks he does.

First of all, he starts out with a picture that supposedly shows the large reduction in max ram height from the straight linkage to the "cam over" position, but the split picture is so obviously misaligned that he is either incapable of actually paying attention to details, or he is deliberately trying to scam the reader and thinks that we are all too dumb to see it. Secondly, he starts right off by labeling the RCBS presses as "cammers", but the test he gives you near the end of the article to tell if you have a "cammer" is complete BS, as it simply proves that the Rock Chucker is not a "cammer".

Technically, the RCBS Rock Chucker press may be a cam-over design, and yes, the instructions do tell you to adjust the die so that the press "cams over center". But taking those facts out of context is misleading. Here is a fact from my personal 70s era Rock Chucker: the maximum height of the ram does not go down as the press "cams over center", or if it does, the amount is so minuscule as to be effectively immeasurable. Yes, the Rock Chucker does have a toggle link connection to the bottom of the ram that moves a considerable distance past the 0 degree vertical alignment with the ram as the handle reaches the full bottom point, but that means NOTHING! All you have to do is actually look at the ram as that toggle link moves past vertical to see that the ram is STILL MOVING UP, not coming back down. In actual fact, the ram on my Rock Chucker reaches the effective maximum height concurrent with the handle bottoming out.

So why do the RCBS die instructions tell you to screw the sizing die in 1/8 turn below where it touches the shell holder? They clearly state that this is simply to "be sure all play is removed from the press leverage system". All moveable joints and connections have play - if they did not, they couldn't move. The more slop or play in the connections on your press, the lower you need to adjust the die to ensure all of that slop is taken out. Properly adjusting the die so that you can just feel it tighten up at the very end of the handle throw is the only way you can ensure all of that play or slack in the joints is taken up for the most uniform sizing from one case to the next. That is true if the press has a linkage system that allows it to "cam over center" or not. Most of us do not need that last nth level of uniformity (I almost never do full length resizing with my RCBS FL dies, so the die never touches the shell holder at all), but for those who want it, any quality press that is sufficiently rigid will do it if the dies are properly adjusted. And most importantly, remember that the die instructions need to work for those dies an any press - even a worn out sloppy piece of junk that you may have inherited from uncle Joe.
 
So why do the RCBS die instructions tell you to screw the sizing die in 1/8 turn below where it touches the shell holder? They clearly state that this is simply to "be sure all play is removed from the press leverage system". All moveable joints and connections have play - if they did not, they couldn't move. The more slop or play in the connections on your press, the lower you need to adjust the die to ensure all of that slop is taken out. Properly adjusting the die so that you can just feel it tighten up at the very end of the handle throw is the only way you can ensure all of that play or slack in the joints is taken up for the most uniform sizing from one case to the next. That is true if the press has a linkage system that allows it to "cam over center" or not. Most of us do not need that last nth level of uniformity (I almost never do full length resizing with my RCBS FL dies, so the die never touches the shell holder at all), but for those who want it, any quality press that is sufficiently rigid will do it if the dies are properly adjusted. And most importantly, remember that the die instructions need to work for those dies an any press - even a worn out sloppy piece of junk that you may have inherited from uncle Joe.
Click to expand...
__________________
I can not imagine a press having .017” slack after contact. The additional ¼ turn after contact increases the presses ability to overcome the resistance of the case being sized. After that there is the linkage getting tangled up once the ram goes to the top. Again the RCBS Rock Chucker linkages limits travel; once that happens the ram is kicked back at the bottom and forward at the top.

I size cases to fit the chamber, I off set the length of the chamber with the length of the case. Again, I have one chamber that requires the die to be backed off of the shell holder .014”. The chamber is .002” longer than a field reject length gage.

F. Guffey
 
I spoke to an RCBS tech, and he recommended just letting my carbide die gently "kiss" the shell holder before the press cams over...just a little "bump", so I do. No problems. If I adjust the die to touch the shellholder after the press cams over, it locks everything up tight!
Examining my sizing die, it appears that the carbide ring is ever so slightly recessed inside the die body, so it would take massive ham-handed adjustments before the ring will be touched. Of course, I haven't examined any other carbide size dies, so it may just be mine.

For my rifle dies, I smoke the case shoulder, and without worrying too much about cam-over, adjust the die till it just barely smudges the smoked area. That has worked well for several rifles, with no stretch or chambering difficulties. I double check the brass with a Wilson case gauge.
 
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IWAC said:
I spoke to an RCBS tech, and he recommended just letting my carbide die gently "kiss" the shell holder before the press cams over...just a little "bump", so I do. No problems. If I adjust the die to touch the shellholder after the press cams over, it locks everything up tight!
Click to expand...
That is interesting - what press do you have? If I understand what you said, that means your press is definitely dropping the ram back down some after the cam over center. My Rock Chucker does NOT do that.
 
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