CAM OVER

[Brians356]

Using a Rockchucker press, I try to set the cam-over consistently at 1/8 turn beyond first contact with the ram, with both standard or Redding competition shell holders. That 45 degs of rotation is easy to eyeball consistently enough.
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[Rustytigwire]

Past bottom and back confirms with certainty extent of travel. H'aint no more without moving metal. Linkage slop another discussion. Same is what matters.
I always think of this.

No i am not a rasta fan.

 

[Brians356]

Past bottom and back confirms with certainty extent of travel. H'aint no more without moving metal.

Metal "moves". Need proof?
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[Alex Wheeler]

Cam over is a way of preloading the press to absorb most of the slop and flex that may be in the system. You will see more consistent bump numbers with a preloaded press.

 

[B23]

Without a slight touch, and or cam over, generally the shoulder will actually be pushed slightly forward and the base to shoulder measurement will increase. Many have a hard time wrapping their brain around that notion, but if shooters would properly measure their brass when sizing, which I'm convinced the vast majority do not, you'll see what I'm talking about.

 

[Nature Boy]

Yeah, he's over. Still a free agent. No one wants to sign him. Excessive headspace

 

[Webster]

Cam over is a way of preloading the press to absorb most of the slop and flex that may be in the system. You will see more consistent bump numbers with a preloaded press.

Somethinng not mentioned. When we adjust for a specific shoulder bump does that mean when the shell holder is all the way up it doesn't touch the die. How else could you adjust bump. Always wondered about cam over. Actually I am not concerned with it. My rifle varmint rifle shoots under .350" without getting into a lot of details.

 

[Uncle Ed]

As long as the die is making hard contact with the shell holder with press camover any slop or give in the press is eliminated. And if you use Redding competition shell holders the press can still camover. And there is no air gap between the die and shell holder and you still control the amount of shoulder bump.

If you want to see a air gap between the die and shell holder then size a Lake City 7.62 case that was fired in a machine gun. Don't forget to use a good case lube and eat your Wheaties, you will get a good workout.

I bought my Rockchucker press in 1973 so there is more slop in the linkage with use and age. And the Redding competition shell holders let you control the amount of shoulder bump and still let the die make hard contact with the shell holder with press cam over.

 

[Alex Wheeler]

If your getting the correct shoulder bump, without cam over (this is common) the redding competition shell holders may help. If the gap is too much, you wont be able to get cam over with the correct bump.

 

[K22]

If you measure a fired case (spent primer removed) using a bump gauge and a caliper then adjust the die to set the shoulder back .001 to .002" (bolt rifles) doesn't that determine the degree of cam over / under required?

At least it's been my experience that adjusting a full length sizing die (up or down) does change the amount of shoulder set back. Also, in some cartridges if the shoulder is not touched the die can extrude the case actually making it longer. I've noticed this especially with the 243 Win and 308 Win.

I also found that the amount of cam over / under can vary with the brand of brass, the rifle, and the age (number of times resized) of the case. In the latter case I check three cases in the lot as the cases age to see if some adjustment is needed.

I use Skip's Shims (available at Sinclair) to make adjustments to the amount of cam over / under. Seems to work fairly consistent and they're not expensive.

German Salazar wrote a very comprehensive and informative article on case full length resizing but I think his blog is no longer active. It might be useful if it could be posted here if he could be contacted and permit the article to be posted on this site.

 

[LCazador]

Webster, if you do not want to accept cam over, then get the Redding comp shell holders or grind .003 off the top of a shell holder and set your sizing accordingly.

what ackleyman says^^^^

 

[J.d. Popkes]

Others obviously have figured out how to get dead nuts exact consistency with shoulder bump without cam over. I am not one of them. Consistent lube process and a little cam over and consistently running the lever is the only way I’ve found.

we’ve tested a few presses and they all flex a couple thou in one way or another depending on linkage configuration. Only way I can see is anneal and steel to steel. Measure 100 cases, all within 1/2 thou which to me is how hard ya push on the guage. My 2 ¢

 

[Brians356]

Webster, if you do not want to accept cam over, then get the Redding comp shell holders ...

Even with those one should be camming over for consistency.

Redding's instructions say "The shellholder should be adjusted to make firm contact with the bottom of the sizing die". I take that as a subtle hint.
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[J.d. Popkes]

Even with those one should be camming over for consistency.

Redding's instructions say "The shellholder should be adjusted to make firm contact with the bottom of the sizing die". I take that as a subtle hint.
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Yes sir. No reason for them if ya ain’t camming. That’s their reason for being.

 

[ronsatspokane]

So I have started to question the entire sizing process. Recently purchased a 6BRA. While fire forming Lapua 6 BR cases that rifle shot better than just about any rifle I have owned. I would have shot it in competition and likely done quite well depending on who showed up and what the conditions were. With other rifles I only neck size and they don't shoot as well. I know people with 6 Dashers who have the same report as far as the way they shoot while fire forming. Rifle shoots lights out. Given that the brass is, in effect, only a gasket, the question arises: Is brass sizing an old wives tale rooted in an era when few rifles would shoot 1/4 MOA?

Please discuss.

 

[bozo699]

So I have started to question the entire sizing process. Recently purchased a 6BRA. While fire forming Lapua 6 BR cases that rifle shot better than just about any rifle I have owned. I would have shot it in competition and likely done quite well depending on who showed up and what the conditions were. With other rifles I only neck size and they don't shoot as well. I know people with 6 Dashers who have the same report as far as the way they shoot while fire forming. Rifle shoots lights out. Given that the brass is, in effect, only a gasket, the question arises: Is brass sizing an old wives tale rooted in an era when few rifles would shoot 1/4 MOA?

Please discuss.

I’m not sure what your trying to say?
Wayne

 

[David Christian]

So I have started to question the entire sizing process. Recently purchased a 6BRA. While fire forming Lapua 6 BR cases that rifle shot better than just about any rifle I have owned. I would have shot it in competition and likely done quite well depending on who showed up and what the conditions were. With other rifles I only neck size and they don't shoot as well. I know people with 6 Dashers who have the same report as far as the way they shoot while fire forming. Rifle shoots lights out. Given that the brass is, in effect, only a gasket, the question arises: Is brass sizing an old wives tale rooted in an era when few rifles would shoot 1/4 MOA?

Please discuss.

I have no idea what dots you are trying to connect with your question.

 

[Brians356]

So I have started to question the entire sizing process. Recently purchased a 6BRA. While fire forming Lapua 6 BR cases that rifle shot better than just about any rifle I have owned. I would have shot it in competition and likely done quite well depending on who showed up and what the conditions were. With other rifles I only neck size and they don't shoot as well. I know people with 6 Dashers who have the same report as far as the way they shoot while fire forming. Rifle shoots lights out. Given that the brass is, in effect, only a gasket, the question arises: Is brass sizing an old wives tale rooted in an era when few rifles would shoot 1/4 MOA?

Please discuss.

I think I follow you. Is tight body to chamber fit overrated? Why not drastically resize cases, back to minimum? After all, what could be more drastically undersized than the 6 BR you started with, and shot so well?

I wonder if the energy consumed expanding the parent case doesn't alter the pressure rise curve to some advantage? It "flattens the curve" (Hey!) and that sometimes, somehow produces better accuracy than the improved case henceforth.
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[David101]

Perhaps you could replace the handle of non cam over presses with a torque wrench as the handle. You could then set the pressure you wanted and get the same pressure each time. I would suggest the type that have say a 1/2 inch square for sockets and the neck of the torque wrench moves or clicks when the correct pressure is achieved.

 

[dgeesaman]

I’m not sure what your trying to say?
Wayne

I think he’s trying to say that fireforming uses brass with huge clearances, as if the brass was grossly over-sized in a die. Yet fireformers can shoot very well at times.

My answer to that is: fireforming 6BRA involves brass that is still very well aligned by the fit at the neck/shoulder junction and/or the bullet jammed in the throat. So yes it’s not surprising it can shoot. Velocity might not be reliable but in short range there are plenty of shooters who shoot fireformers in fun matches.

David