Cam over?

DAA

Administrator
Staff member
Have noticed lately a couple of you mentioning cam over as evil and to be avoided.

Mildly curious as to why?

I do not often need to do any shoulder bump or FL sizing, so cam over isn't often even a consideration.

But, when I do need to shoulder bump or FL size, I much prefer to have a firm, positive cam over rather than any gap between shell holder and die. Just eliminates potential variables, is how I see it. Taking out any slack and getting firm contact between shell holder and bottom of the die provides a mechanical stop that assures every case is getting precisely the same amount of persuasion from the die.

To me, leaving any gap, means you better have your lube program really dialed in. Which is not hard to do, but simple lube variation can easily lead to variable sizing operation since there's no mechanical stop via the shell holder. Again, not hard to deal with, but, it needs to be dealt with. Whereas a solid cam over, this is a non-issue, no room for a variable to be introduced.

I'm sure you guys have this all figured out, not trying to start anything. I know you can get very consistent results without any cam over. Just, like I said, curious what is the potential harm or variable introducing I am not seeing with cam over that you feel it's best avoided?

- DAA
 
With ar15s you need a certain amount of shoulder bump for proper feeding. I just set my die up to provide the minimum amount of bump needed for feeding so I can be as easy on brass as possible. I don't know of any dies I have currently that need to be set down to the shell holder to get the correct headspace.

Btw...I'd like to know what exactly is defined by "cam over." My ram/lever will "cam over" by my definition unless I fail to make a full stoke of the lever.
 
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I don't think we are talking about camming over with a gap between the shell holder and the die, that's just using the handle stop to finish the stroke, I think we are talking about camming over after the die has contacted the shell holder.

Brass is pretty soft stuff, you can easily make die to shell holder contact without camming over. Once you make die to shell holder contact all your doing is stressing the press, steel to steel isn't going to compress any farther. I do some pretty radical case forming and never have to cam over to do it. You can literally stand on a press handle and not stress a press as much as you would camming over because at that point the mechanical advantage is so great.

I do have Redding Competition shell holders that are graduated heights so I can adjust set back and I've been known to surface grind a shell holder for a tight chambered gun. You can also shim shell holders.

I've been loading for 50 yrs now and started with C-presses, I don't remember them being able to cam over, it would have broke a lot of presses. I think I could still load happily on a C-press if I didn't do case forming and bullet swaging.
 
Originally Posted By: midwestpredatorWith ar15s you need a certain amount of shoulder bump for proper feeding. I just set my die up to provide the minimum amount of bump needed for feeding so I can be as easy on brass as possible. I don't know of any dies I have currently that need to be set down to the shell holder to get the correct headspace.



Good illustration of how application specific things always are. I've never loaded for an AR. My bolt guns, I don't FL size or shoulder bump until it's needed, which for some of them is actually never. It's not very often for any of them.

But, when I do, as it turns out - I didn't plan this, but of my current crop of regularly used bolt guns and the dies I have for them, good firm cam over gives about .002 shoulder bump. Kind of just lucky, kind of not, since the chambers are all custom and sized for the brass intended to be used in them.

I've got the Redding + thickness shell holders to take up the slack if needed. So I'll have cam over even if the die needs to be backed off. But, don't currently own a rifle/die combo that needs them.


Originally Posted By: midwestpredator
Btw...I'd like to know what exactly is defined by "cam over." My ram/lever will "cam over" by my definition unless I fail to make a full stoke of the lever.

What I mean by cam over is the shell holder making enough contact with the bottom of the die that you can't finish the press stroke without putting just a tiny bit of flex into the press. It feels like the eccentric on a compound bow letting off when you overcome the little bit of resistance and the press handle falls freely the last bit of travel.

- DAA
 
Originally Posted By: AWSI don't think we are talking about camming over with a gap between the shell holder and the die, that's just using the handle stop to finish the stroke, I think we are talking about camming over after the die has contacted the shell holder.


That is exactly what I meant.

Curious what the issue, or problem, or variable that might get introduced is by camming over. What is the reason for avoiding it?


Originally Posted By: AWS Once you make die to shell holder contact all your doing is stressing the press, steel to steel isn't going to compress any farther.


And this is exactly why I like to have positive cam over. Steel to steel is consistent. I guess you can do it without camming over, but camming over is a lot easier.

What's the downside? Stressing the press? It's how they are engineered to be used. You can't hurt one using it that way if you have any sense at all.

I've been using the same O frame Pacific press for almost 40 years now. Have worn out quite a few barrels with ammo all loaded on that press. I know that it is actually possible to spring a press, and not even that hard to do with a C press. But you'd have to be a major league idiot to pull it off with an O frame. You just aren't ever going to hurt one using it for normal cam over sizing and in fact that is exactly what the manufacturers all tell you to do (for the wrong reasons, but that's a different subject...).

There's got to be a better reason than stressing the press to avoid cam over? Because that's a complete non-issue.

- DAA
 
Originally Posted By: AWSI don't think we are talking about camming over with a gap between the shell holder and the die, that's just using the handle stop to finish the stroke, I think we are talking about camming over after the die has contacted the shell holder.

Brass is pretty soft stuff, you can easily make die to shell holder contact without camming over. Once you make die to shell holder contact all your doing is stressing the press, steel to steel isn't going to compress any farther. I do some pretty radical case forming and never have to cam over to do it. You can literally stand on a press handle and not stress a press as much as you would camming over because at that point the mechanical advantage is so great.


Exactly.

A few years ago I was trying to bump the shoulder back on a once-fired case from a new rifle. The chamber had been cut tight enough for a crush fit on new Lapua brass.
I lowered the handle to the bottom to raise the shell holder on the Co-ax press to the top, and then screwed the new Forster FL die tight against the shell holder.
First time in the die-no change. So I tightened the die down another 1/8 of a turn to get the "cam over".
Second time in the die-no change, and I could feel the stress on the press.
When a hardened steel shell holder makes full contact with a hardened steel die, that's as far as it goes.

Camming the press over past that point will not size the brass even .0005 more.
 
Originally Posted By: fw707

When a hardened steel shell holder makes full contact with a hardened steel die, that's as far as it goes.

Camming the press over past that point will not size the brass even .0005 more.



Well... That's exactly why I LIKE cam over? I mean, that's a good thing, right? What's the downside? Why avoid it?

Obviously, I'm talking about properly adjusted dies here. Not indiscriminately screwing dies down for good firm cam over "just because". I'm talking having them adjusted perfectly as the first priority, but very much preferring that there be a good firm contact of shell holder to die at that point. It's dead nuts consistent.

- DAA
 
Dave,
I think we're on the same page. The slight cam over you are doing for consistency isn't like cranking things down trying to change brass dimensions.
 
Originally Posted By: DAAOriginally Posted By: midwestpredatorWith ar15s you need a certain amount of shoulder bump for proper feeding. I just set my die up to provide the minimum amount of bump needed for feeding so I can be as easy on brass as possible. I don't know of any dies I have currently that need to be set down to the shell holder to get the correct headspace.



Good illustration of how application specific things always are. I've never loaded for an AR. My bolt guns, I don't FL size or shoulder bump until it's needed, which for some of them is actually never. It's not very often for any of them.

But, when I do, as it turns out - I didn't plan this, but of my current crop of regularly used bolt guns and the dies I have for them, good firm cam over gives about .002 shoulder bump. Kind of just lucky, kind of not, since the chambers are all custom and sized for the brass intended to be used in them.

I've got the Redding + thickness shell holders to take up the slack if needed. So I'll have cam over even if the die needs to be backed off. But, don't currently own a rifle/die combo that needs them.


Originally Posted By: midwestpredator
Btw...I'd like to know what exactly is defined by "cam over." My ram/lever will "cam over" by my definition unless I fail to make a full stoke of the lever.

What I mean by cam over is the shell holder making enough contact with the bottom of the die that you can't finish the press stroke without putting just a tiny bit of flex into the press. It feels like the eccentric on a compound bow letting off when you overcome the little bit of resistance and the press handle falls freely the last bit of travel.

- DAA


I would agree with your definition. So I get that same effect while FL sizing even without shell holder contact. Now it is obviously going to be less of an effect but I find that as long as I am bumping the shoulders the effect is there.

Maybe the big difference in your case compared to mine is that neck sizing only doesn't provide the resistance needed to get any real amount of resistance in the press stroke/linkage? I've never neck sized only with a neck size die. I've tried it with a fl die backed off to not bump but that's a whole other taboo topic it seems.
 
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Originally Posted By: DAAOriginally Posted By: fw707

When a hardened steel shell holder makes full contact with a hardened steel die, that's as far as it goes.

Camming the press over past that point will not size the brass even .0005 more.



Well... That's exactly why I LIKE cam over? I mean, that's a good thing, right? What's the downside? Why avoid it?

Obviously, I'm talking about properly adjusted dies here. Not indiscriminately screwing dies down for good firm cam over "just because". I'm talking having them adjusted perfectly as the first priority, but very much preferring that there be a good firm contact of shell holder to die at that point. It's dead nuts consistent.

- DAA

Now I'm not trying to argue with your method because I can see the logic but simply wanting to further the discussion....

When you say steel to steel is dead nuts consistent, is that length of travel going to be all that much different that the full throw or stroke of the ram? If the ram travel 4 inches and as long as the lever is ran for a full stroke would that not still be theoretically as consistent as when made to have firm contact with the die and shell holder?
 
When you grind a shell holder, where are you removing material from? And what is the result? I have rcbs (rc) presses all but one old used ones,I adjust my dies up or down to size neck or full length. I run rcbs,hornady(not my favorite),Redding,and Lee dies. I don't mix shellholder and die brands( only time I have damaged a case).
 
Originally Posted By: midwestpredator

I would agree with your definition. So I get that same effect while FL sizing even without shell holder contact. Now it is obviously going to be less of an effect but I find that as long as I am bumping the shoulders the effect is there.



Well, for me, what I'm talking about has nothing at all to do with the amount of sizing. I just take it for granted that we all are talking about properly adjusted dies for the amount and type of sizing required.

The phrase "cam over", unfortunately does get mixed up with "die adjustment". But I see them as two distinctly separate issues. Separate, but they do often conflict with each other.

When they do conflict, proper adjustment is obviously always the first priority. If the equipment ends up with a gap between shell holder and die when everything is properly adjusted, then so be it.

The reason I started this thread, is that it's my impression some of you see hard contact and cam over as an inherently bad thing, on it's own merit. It sounds like they'd take a situation where they are getting precisely the amount of sizing that they want with cam over and then grind the shell holder just to not have the cam over. That's what I'm curious about. What is the problem solved or avoided by not having cam over? What is the inherent issue?



Originally Posted By: midwestpredator

Maybe the big difference in your case compared to mine is that neck sizing only doesn't provide the resistance needed to get any real amount of resistance in the press stroke/linkage?

No, no, no... I don't care about cam over when neck sizing, a lot of my neck sizing dies aren't intended to have cam over. It's only when FL sizing or shoulder bumping that I see an inherent benefit to cam over.

That said... It's a pretty minor thing. Can get where you want to go by either route. But, it piqued my curiosity and it's actually something that hasn't been talked about a million times here already, so I thought I'd ask. And glad I did. Still haven't had my question answered, but that's okay.

- DAA
 
Originally Posted By: fw707Dave,
I think we're on the same page. The slight cam over you are doing for consistency isn't like cranking things down trying to change brass dimensions.

Ahh... I may be just on glue after all
laugh.gif
. I thought, just an impression, don't think you guys clearly said so, but I had the impression you preferred a gap between the shell holder and die and were avoiding cam over for the sake of avoiding it. And I was really curious why.

- DAA
 
Originally Posted By: midwestpredatorOriginally Posted By: DAA

...very much preferring that there be a good firm contact of shell holder to die at that point. It's dead nuts consistent.

- DAA

Now I'm not trying to argue with your method because I can see the logic but simply wanting to further the discussion....

When you say steel to steel is dead nuts consistent, is that length of travel going to be all that much different that the full throw or stroke of the ram? If the ram travel 4 inches and as long as the lever is ran for a full stroke would that not still be theoretically as consistent as when made to have firm contact with the die and shell holder?

Well.... So how much is "all that much" and how consistent is consistent, right?

I think for the big majority of us, we're talking small potatoes here. Not much difference at all. But, some. Probably not enough to make any difference in most rifles. But, still, the theoretical difference is there. And even that theoretical difference, can be minimized with good practices.

Lubrication and brass hardness being the two real obvious variables as sources for inconsistency. The potential for inconsistency being mitigated by cam over. But it's small stuff, it really is.

End of the day, not likely to make any difference to anyone. Bordering on how many angels can dance on the head of a pin type stuff.

But, just in case it maybe isn't clear how lube or hardness can effect sizing consistency...

That same little tiny bit of flex in the press that happens when you cam over. Well, that press flex can happen anytime there is enough force on the ram. With cam over, you use that flex to make sure you have a steel to steel contact that is extremely consistent.

With enough force on the ram, the press still flexes well before cam over. I'm sure most of us have seen enough press flex to be noticeable before the shell holder even touched the die.

So, you just have to take steps to make sure it flexes consistently from case to case to avoid these small sizing variables talked about. The two real easy ways to cause a press to flex before cam over and to have that flex be inconsistent, are by varying amounts of lube on cases and brass hardness.

A case with not enough lube, will take more force to push into the die and easily enough force to cause the press to flex. This is very, very common actually. So, without cam over, if you were to measure that gap between the top of the shell holder and the bottom of the die, you'd find it varies by a tiny bit from one case to the next if the lube isn't properly done.

Same thing with varying brass hardness. Not an issue for most of us, but for the mixed head stamp folks, it's common. But they aren't loading for precision anyway and would never notice these small variables in sizing operation.

Honestly, almost nobody would notice them except in extreme instances. It was a thread I read this morning about just such an extreme instance though, where I noticed the talk of avoiding cam over.

- DAA
 
Originally Posted By: DAAOriginally Posted By: fw707Dave,
I think we're on the same page. The slight cam over you are doing for consistency isn't like cranking things down trying to change brass dimensions.

Ahh... I may be just on glue after all
laugh.gif
. I thought, just an impression, don't think you guys clearly said so, but I had the impression you preferred a gap between the shell holder and die and were avoiding cam over for the sake of avoiding it. And I was really curious why.

- DAA

No, I don't necessarily prefer a gap.
A solid contact like you use would be fine with me-
But all of my dies are set up with a gap because I sent the shell holder plates from both my Co-ax presses to a gunsmith with a precision surface grinder and had .010 taken off the top surfaces.
It was either the dies or the shell holders, so shaving down the shell holders was the easy fix.
All my dies are Forster FL and I have them set up for a .002 shoulder bump. When my brass comes out of the dies my bump gauges show .0015 or .002, and that's as close as my cheap calipers can measure.
My loads always function just fine, and I have worn out a barrel with 100 pieces of brass.





 
I like to set my LCT's for what I consider "cam over," meaning I don't just "kiss" the ram cam stops, I push against them. Typically, I don't end up having contact against the shell holder - but when I have a physical dead stop at the bottom, confirmed by more than "sizing pressure" against the handle,I know the case in the die at the top end is no larger than the dimension allowed between the die and the shell holder base. It could be smaller, of course, but it could be so no matter what I did with the ram. In the LCT's, I like to know I've consistently pressed the bottom of the stroke such I have my best opportunity of pressing consistent "slop" out of the top of the system in the turret head. It's that one-in-twenty cases that want to stick in the last 1/10th of an inch or less, where my hand might not feel the difference in a slight stick and a kiss against the ram cam stops, and those 1 in 20 end up a little overlength. My hand ALWAYS can feel the difference between my "cam over" pressure and sticking case pressure, or "kiss the stops" pressure.

Stressing the press... I'm sure it does... I've loaded hundreds of thousands of rounds on one of my LCT's, and it's a $125 item if it ever gets sloppy (if Lee left me hanging). Even for my Co-ax's, they're far less expensive than the volume of ammo I have loaded with them - the press is a cheap part, no reason to cry if it decided to be relatively consumable. But since I've loaded somewhere over 2million rounds on various presses over the years without ever wearing out a press, I'm not complaining about press life.
 
Originally Posted By: DAAOriginally Posted By: midwestpredatorOriginally Posted By: DAA

...very much preferring that there be a good firm contact of shell holder to die at that point. It's dead nuts consistent.

- DAA

Now I'm not trying to argue with your method because I can see the logic but simply wanting to further the discussion....

When you say steel to steel is dead nuts consistent, is that length of travel going to be all that much different that the full throw or stroke of the ram? If the ram travel 4 inches and as long as the lever is ran for a full stroke would that not still be theoretically as consistent as when made to have firm contact with the die and shell holder?

Well.... So how much is "all that much" and how consistent is consistent, right?

I think for the big majority of us, we're talking small potatoes here. Not much difference at all. But, some. Probably not enough to make any difference in most rifles. But, still, the theoretical difference is there. And even that theoretical difference, can be minimized with good practices.

Lubrication and brass hardness being the two real obvious variables as sources for inconsistency. The potential for inconsistency being mitigated by cam over. But it's small stuff, it really is.

End of the day, not likely to make any difference to anyone. Bordering on how many angels can dance on the head of a pin type stuff.

But, just in case it maybe isn't clear how lube or hardness can effect sizing consistency...

That same little tiny bit of flex in the press that happens when you cam over. Well, that press flex can happen anytime there is enough force on the ram. With cam over, you use that flex to make sure you have a steel to steel contact that is extremely consistent.

With enough force on the ram, the press still flexes well before cam over. I'm sure most of us have seen enough press flex to be noticeable before the shell holder even touched the die.

So, you just have to take steps to make sure it flexes consistently from case to case to avoid these small sizing variables talked about. The two real easy ways to cause a press to flex before cam over and to have that flex be inconsistent, are by varying amounts of lube on cases and brass hardness.

A case with not enough lube, will take more force to push into the die and easily enough force to cause the press to flex. This is very, very common actually. So, without cam over, if you were to measure that gap between the top of the shell holder and the bottom of the die, you'd find it varies by a tiny bit from one case to the next if the lube isn't properly done.

Same thing with varying brass hardness. Not an issue for most of us, but for the mixed head stamp folks, it's common. But they aren't loading for precision anyway and would never notice these small variables in sizing operation.

Honestly, almost nobody would notice them except in extreme instances. It was a thread I read this morning about just such an extreme instance though, where I noticed the talk of avoiding cam over.

- DAA

I don't have an answer for your original question and I guess I was playing a little devils advocate.

You brought up a good point, one that I had not considered. I was only figuring the variance in ram/linkage in the equation and my point was as you stated, that the variance would be so small as to be undetectable by the vast majority.

Also, I couldn't agree more in that proper sizing per chamber would be the most important above all. At any rate, I think I may pickup a set of the Redding shell holders to play around with and see if I can measure any improvement in consistency vs what I have been doing.
 
I don't grind shell holders to avoid cam over I grind, shim or use oversized shell holders so my head space is perfect for that rifle when the die hits the shell holder. I adjust my dies so the hit the shell holder long before I would get into cam over situation. I can use the same die for multiple different rifles by using the shell holder for that rifle, no adjusting needed, just screw the die in until it hits the shell holder somewhere before the bottom of the stroke.
 
Many years ago when I had three different factory .22-250's at the same time I did something similar to avoid adjusting the die for each of them.

- DAA
 
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