rcbs full length die and cam over...

GW Hunter

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I'm helping a buddy load ammo for his 300 weatherby mag using his RCBS full length die. The die is set per the instructions to cam over. This is pushing his shoulder back further than wanted. If you back the die out to reduce the set back, does this affect the resizing process at the bottom of the case? Will you get a build up of brass at the belt? Thanks for any and all replies...
 
Cam over can be a broad process. I would back the die out until you get the desired shoulder setback, then determine if it still has firm contact with the shell holder.
Even a light cam over is still cam over.
Setting up a die with firm cam over on a belted case, will usually always size the case too much,
I would set it up to set the shoulder back .002" and not worry too much about firm cam over per instructions.
 
So is cam over more about the die and shellholder squaring up to each other?
Yes, it will ensure consistency.
The problem with belted cases, is true headspace is set off the belt, which is too much for case life. Depending on your chamber, camover may not happen with your current set up.
 
So is cam over more about the die and shellholder squaring up to each other?

Cam over removes any slop in the press and reduces variations in shoulder location.
Redding makes "Competition shell holders" with five shell holders that allows the press to cam over and push the case from .002 to .010 less into the die. You never have to adjust the die up or down for the correct amount of shoulder bump. And you just change the shell holders in .002 increments to adjust the shoulder bump and still have cam over.

Before this you used feeler gauges placed between the die and shell holder to reduce the amount of shoulder bump when adjusting the die. "BUT" with the feeler gauge air gap between the die and shell holder you will have no cam over and slop in the linkage. This varies with press design and age, my 45 year old Rockchucker has a little slop and the competition shell holders allows the press to cam over and control the amount od shoulder bump.

7FfXhJ7.jpg


The Redding competition shell holders lower the deck height where the base of the case rests to reduce the amount of shoulder bump. Meaning these shell holders do not push the case into the die as far as a standard shell holder.

k8hyF40.jpg


Competition Shellholder Sets
http://www.redding-reloading.com/online-catalog/35-competition-shellholder-sets

Now you can control headspace. The new Redding Competition Shellholders are packaged in five piece sets in .002" increments (+.002", +.004". +.006", +.008" and +.010"). Each shellholder has a distinct black oxide finish and is clearly marked to indicate the amount it will decrease case-to-chamber headspace. You can now easily adjust the shoulder bump to customize cases to your specific chamber.
 
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if you load hot ,the web can over expand in time or using brass from a different rifle ,that's where a collet die really helps, had a Vangard WBY for years in 300 BEE! great cartridge enjoy . redding prints 2 great examples of how to set up any FL-die for any magnum or non magnum case.
 
I'm helping a buddy load ammo for his 300 weatherby mag using his RCBS full length die. The die is set per the instructions to cam over. This is pushing his shoulder back further than wanted. If you back the die out to reduce the set back, does this affect the resizing process at the bottom of the case? Will you get a build up of brass at the belt? Thanks for any and all replies...
This is why neck-sizing brass makes life so much simpler...Especially with belted magnums, because it headspace off the belt, not the shoulder.
 
The simple fact is that cam over is NOT always desirable.
The easiest way to determine HOW MUCH sizing is required is to index your lock ring with 1/12 marks, each represent about .004" adjustment in height. Back the die out 1/2 turn from touching the shell holder and make a mark on the press and the die. Size a case, clean it, chamber it, if it is TIGHT to close the bolt, screw the die IN 1/12 as indicated by your lock ring indexes, repeat until a slight feel is felt on bolt turn down, then screw the die IN an additional 1/24 turn, this should give you around .002" shoulder bump.
I run a few Weatherby cases, I will tell you that this design resists sizing moreso than angled shoulders and can be a PITA to get right, sometimes you need to bump more than .002" to give reliable chambering.

Hope this helps.

Cheers.
:)
 
The simple fact is that cam over is NOT always desirable.
The easiest way to determine HOW MUCH sizing is required is to index your lock ring with 1/12 marks, each represent about .004" adjustment in height. Back the die out 1/2 turn from touching the shell holder and make a mark on the press and the die. Size a case, clean it, chamber it, if it is TIGHT to close the bolt, screw the die IN 1/12 as indicated by your lock ring indexes, repeat until a slight feel is felt on bolt turn down, then screw the die IN an additional 1/24 turn, this should give you around .002" shoulder bump.
I run a few Weatherby cases, I will tell you that this design resists sizing moreso than angled shoulders and can be a PITA to get right, sometimes you need to bump more than .002" to give reliable chambering.

Hope this helps.

Cheers.
:)
 
Thanks for the input. I'm familiar with the procedure of sizing a case to match a chamber but have wondered if not running the ram to cam over would not completely resize the case near the belt.
 
Thanks for the input. I'm familiar with the procedure of sizing a case to match a chamber but have wondered if not running the ram to cam over would not completely resize the case near the belt.
Unfortnately the die, whether used as described above, or FL sizing back to minimum SAAMI specs, is still sizing the body smaller, even down to the belt. It is a myth that the die doesn't or can't size the entire body, as it is evident where the sizing stops at the expansion line. The belt itself is part of the solid head and cannot be sized anyway.
This causes the head to shoulder dimension to grow, which we then need to bump back.
I have sectioned many belted cases, the expansion line gets closer to the belt on brass that is either thinner in the walls or thinner in the web. The worst culprit being Norma brass. It is often hard to distinguish where the expansion line is on Norma brass as the solid section of the case head ends right at the front of the belt, this can cause the bulge to happen if the chamber is loose in this area.
Whether you get the so called 'bulge' above the belt is partly due to your chamber design, brass brand you use AND sizing method.
I have not experienced the bulge in ANY of my belted magnums and I have/do run quite a few of them. To date, I have used 270 Weatherby, 264WM, 300 Weatherby, 340 Weatherby, 300WM, 338WM and 375 Weatherby. As well as 458WM and 458 Lott. Which are sized differently.

The only case I have trouble with is my custom 375 Weatherby, it has a very tight match grade chamber, I had to buy 3 different die sets and modify a shell holder by turning .010" off the top of it before I could get sized brass to chamber, as the chamber is .002" above minimum CIP spec, and most US dies are too long in head to shoulder length. Even with considerable cam over, the shoulder just wasn't being bumped back due to the cases lengthening during sizing. Feeler gauges under the case head worked, but it was fiddly and slow, hence the need to experiment with different dies. In the end the only set that worked were Redding.

If you think you are getting the bulge after a few firings, there is the belted mag collet die that can help, personally, I don't see any need for it, but each to their own.

Cheers.
:)
 
Unfortnately the die, whether used as described above, or FL sizing back to minimum SAAMI specs, is still sizing the body smaller, even down to the belt. It is a myth that the die doesn't or can't size the entire body, as it is evident where the sizing stops at the expansion line. The belt itself is part of the solid head and cannot be sized anyway.
This causes the head to shoulder dimension to grow, which we then need to bump back.
I have sectioned many belted cases, the expansion line gets closer to the belt on brass that is either thinner in the walls or thinner in the web. The worst culprit being Norma brass. It is often hard to distinguish where the expansion line is on Norma brass as the solid section of the case head ends right at the front of the belt, this can cause the bulge to happen if the chamber is loose in this area.
Whether you get the so called 'bulge' above the belt is partly due to your chamber design, brass brand you use AND sizing method.
I have not experienced the bulge in ANY of my belted magnums and I have/do run quite a few of them. To date, I have used 270 Weatherby, 264WM, 300 Weatherby, 340 Weatherby, 300WM, 338WM and 375 Weatherby. As well as 458WM and 458 Lott. Which are sized differently.

The only case I have trouble with is my custom 375 Weatherby, it has a very tight match grade chamber, I had to buy 3 different die sets and modify a shell holder by turning .010" off the top of it before I could get sized brass to chamber, as the chamber is .002" above minimum CIP spec, and most US dies are too long in head to shoulder length. Even with considerable cam over, the shoulder just wasn't being bumped back due to the cases lengthening during sizing. Feeler gauges under the case head worked, but it was fiddly and slow, hence the need to experiment with different dies. In the end the only set that worked were Redding.

If you think you are getting the bulge after a few firings, there is the belted mag collet die that can help, personally, I don't see any need for it, but each to their own.

Cheers.
:)
Thanks so much for the reply. I think I get it.... so basically the case gets fully resized even if you do not cam over...
 
I struggled with the RCBS cam over press for years and finally gave up in frustration trying to get consistency.... More trouble than they're worth in my opinion.
 
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