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Old 01-03-2022, 04:51 PM   #1
Stan R
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Default RCBS Rock Chucker Cam Over

Just got on older Rock Chucker from my brother. When the handle is pushed down it reached the top just before the handle is at the bottom. It then lowers just a little.

I have Lee Precision Dies (4 dies). I installed the dies per Lee's instructions.

When you raise the ram to the top it hit the dies then it take a lot of effort to completely lower the handle to the bottom. It take almost as much effort to lower the ram. I understand that this is called CAM OVER.

I noticed that the sized brass had a small line at the widest part of the shoulder. You could feel it with your finger nail. I was not sure that was correct. So I stopped.

Is cam over needed or can you adjust the dies to not have cam over and still do the sizing correct.

I decided to size all the brass because I mixed a batch from another 308 rifle.

I did order a length/head space gauge. that will be here tomorrow.

Any suggestions would be appreciated.

Thanks

Any suggestions would be appreciated.
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Old 01-03-2022, 04:52 PM   #2
Stan R
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Pic of brass





The one on the left is the cam over sizing


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Old 01-03-2022, 05:10 PM   #3
Mike D
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Just from the looks of what I can see it looks like you are pushing the shoulder way too far back. .002-.003 is all you really want in a hunting rifle.


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Old 01-03-2022, 05:29 PM   #4
Stan R
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The one on the left is with the over cam. The right is with the dies adjusted back some.
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Old 01-03-2022, 07:04 PM   #5
PantherCity
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Default RCBS Rock Chucker Cam Over

Looks like youíre oversizing, donít adjust the dies with cam over as your goal, a .002 shoulder bump should be your goal. You should set your sizing die with the help of shoulder comparator you ordered.

I would recommend you watch some of Pan handle precisionís YouTube videos before you go any further.


Also as a rule nothing should take a lot of effort, that means something is wrong.

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Old 01-03-2022, 07:19 PM   #6
Matt_C
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^^^^ agree with PantherCity. Watch Sam Milliard (panhandle precision on youtube. He's a master reloader and explains things so even I could understand him.
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Old 01-04-2022, 07:18 AM   #7
muzzlebrake
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Have you attempted to chamber one of these resized cases to see if the bolt will close easily? If they do chamber easily then load and shoot them but next time you load them back off the cam over and use the comparator as described above. If they won't chamber at all then you got a problem. If they do chamber but are sticky on bolt close, just shoot with 10-15% reduced loads to re-fireform the cases.
All dies and presses are not created equal. Some of my dies require a hard cam over to get a .002 set back and some require hardly any cam over to get the .002 set back. Same thing with my presses. Just depends on which dies in what press. I don't know how I got by for so many years without case comparator tools and a digital caliper. I do know that since I got all the right measuring stuff my shot group accuracy improved a lot.
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Old 01-04-2022, 07:35 AM   #8
Stan R
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I ordered the Hornady set that goes on calipers.

Huge learning curve.
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Old 01-04-2022, 07:59 AM   #9
SabreKiller
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Agree with the others that you've got too much shoulder pushback. Generally, you only want to set the shoulder back .002-.003 as mentioned above. I only set mine back .002 and use the comparator to check and adjust my sizing dies.

That being said, if you adjust the sizing die according to the instructions it will say to raise the ram to its highest point, screw the sizing die down until it hits the ram and then back off the ram a little and screw the die down and additional 1/8-1/4 turn. That should give you sufficient shoulder set back. Lock the die in place and you should be good to go.
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Old 01-04-2022, 08:22 AM   #10
M16
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Those of y’all saying .002 shoulder bump are forgetting that some of his brass was fired in other guns. He needs to size them down to where they will chamber in his current gun. He may not have to bump the shoulder at all. After the brass is fired in his current gun then bump .002-.003.
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Old 01-04-2022, 08:23 AM   #11
softpoint
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When you set your press and die to "cam over", you are sizing your cases to minimum dimensions. If you are sizing a batch of brass from unknown or several rifles, this is OK. It basically sizes back to factory ammunition specifications. I do this on cartridges like my .308's and .223's because they will be fired in more than one rifle. You don't need a lot of "cam over" effort, the Rock Chucker has a tremendous amount of leverage. (I have three mounted on my bench right now) Once those rounds are fired in your rifle, if you are reloading for that same rifle, you don't need to size them that far. Back off your die so it just bumps the shoulder, or sets it back a couple of thousandths, and you are good to go.
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Old 01-04-2022, 09:15 AM   #12
GregO
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If you are using the Lee FL sizing die (not collet), then you need to stop when the shell holder touches the die. Any additional pressure can deform the brass, exactly as you have described. There are literally hundreds of advanced techniques that you may or may not decide to employ as advance in your skill set. My suggestion is that you focus on the basics. Your goal should be to produce a quality/safe round that is just as good as a factory round and works in any rifle chambered for that round. Follow the instructions for the die, press, and every other piece of equipment that you are using. Once you have that down, you will begin the never-ending pursuit of perfection. (like everyone else that reloads) Be sure to use good data, verified by multiple sources. The quest for perfection starts with making small changes to your load and tracking performance (gains and losses). You will start with making adjustments to your components, brass, primers, powder, charge weight, bullets…(just like everyone else has.) You will quickly learn and advance your knowledge. When you have the basics down pat, then you can start looking at more advanced techniques and you will have a better idea of how, when and why. After that, the options are endless. There have been books written on just the topic of case prep, which is what you are asking about here. You can’t start out by knowing everything, nor would you want to. Start with the basics, and then decide where to go from there (and how far).

Last edited by GregO; 01-04-2022 at 09:35 AM.
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Old 01-04-2022, 09:18 AM   #13
muzzlebrake
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Quote:
Originally Posted by M16 View Post
Those of yíall saying .002 shoulder bump are forgetting that some of his brass was fired in other guns. He needs to size them down to where they will chamber in his current gun. He may not have to bump the shoulder at all. After the brass is fired in his current gun then bump .002-.003.
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