Cam over pressure ?

[Elroy]

Sorry the title is supposed to read "CAM over pressure". I tried to edit it but couldn't...When you set up sizing dies on a press that cams over is it necessary to get a hard cam over to completely full length size a case,or will a lighter cam over feel accomplish the same results. In my mind I am thinking that as long as the ram is stopping dead enough against the die to initiate cam over it is enough,but I want to be sure. Thanks

[BK7saum]

I very seldom have my sizing dies (rifle) screwed in enough to have a hard cam over. I bump shoulders 0.001-0.002" and this usually occurs with the die slightly off the shellholder. I don't screw carbide pistol dies in to cam over because it can crack the carbide ring.

So...I guess I'm saying that I don't set my presses to cam over unless I need it to bump the shoulder 0.001-0.002"

Brad

[BK7saum]

I measure fired cases with a comparator to get a number/measure of shoulder distance and set the die up in the press to so that the shoulder gets slightly bumped. That number being 0.001-0.002" less that the measurement of the fired case is all that matters.

[Bazoo]

I full length size most rifle brass so, I set it for a medium bump. I make sure on pistol dies with carbide rings that it doesn't contact the carbide. Some of them I've seen has the carbide recessed a bit so it doesn't touch.

[fredj338]

Once the press cams over 0.001-0.002", more isnt moving the die anymore, just stressing the press.

[Win94ae]

The cam over is so you know that the press has gone the total distance; whereas, it starts going back down.

Cam over, is cam over; it is either camming-over, or it isn't. There isn't a "pressure" to it.

[Elroy]

Thanks for the advice folks.

[Greg S]

BK7 hit the nail on the head!. Not all dies and chambers are created equally.

Brand new 308 generally runs SAMMI -.003 to .004. I shoot it in my 308 and it grows to SAMMI + .004-.006. I neck size first time and it comes out after firing at +.007. I re-size bumping shoulder back to +.005-.006.

First firing case grows .009-.010
Second and subsiquent reloadiings .002

If is was to go to SAMMI 0.0

First time .010
Second .006-.007. (may not get full expansion) for each subsiquent reloading.

If I turn my die down to get hard contact I can get SAMMI -.002 on this body die. I've had a set of 223 dies that I could get SAMMI -.006.

Brass is not cheap as it once was and using premium brass is upward of 70 cents to 1.xx +. Do yourself a favor and get some shoulder datum point measuring g adapter for your calipers or borrow one from a friend set up for your brass. Measure some factory, once fired and your reloads and see what you get. Never had a problem with an AR or bolt chambering a round and locking. AR picking ammo is .002 under my smallest chamber. Match AR is .002 under that specific chamber.



If I re-si brass out of a 308 that is SAMMI 0.0 + .007 my cases grow quickly yet re-sizing

[RU shooter]

When you can see no daylight between the die and shell holder with a case inserted is as far as it's gonna go wether it's "camming " over at the bottom of the stroke or not is dependand on how you adjust your die

[rbuck351]

I don't cam over at all. I set my dies so the neck gets sized just shy of the shoulder. I like to just feel the bolt close on a loaded round as in .000 to -.0005 head space. Once the case grows to a slightly stiff bolt closing then screw the die down just enough to get a slight resistance on the bolt. Lock the die ring and leave it. Minimum amount of sizing, maximum case life. If it takes cam over to chamber a round, I trim the shell holder just a bit. I have a 308 I built that has -.005 head space on factory rounds to keep the resizing of new brass to a minimum. I don't want loaded rounds sloppy in the chamber nor do I want them stretching any more than necessary. This requires keeping the chamber and ammo clean so may not be for everyone.

[jsizemore]

The only time cam over would be necessary is if you brass was loaded so hot that you had case head expansion.

[JSnover]

In my mind I am thinking that as long as the ram is stopping dead enough against the die to initiate cam over it is enough,but I want to be sure. Thanks

Correct. You don't want a 'hard' cam-over, it means you're doing something wrong.

[high standard 40]

Like Bk7 said. Sometimes you shouldn't cam over at all to full length resize. My brother recently did that for a newly acquired rifle and the result was excessive headspace. I size just enough so that a cartridge will chamber with slight resistance.

[Elroy]

Correct. You don't want a 'hard' cam-over, it means you're doing something wrong.

I appreciate all the good advice from you all..
The other presses I have owned were not cam over types. They just stopped dead,and I always set my dies at about a quarter turn down after they contacted the shell holder at full ram extension. I do the same on my new press,and it is too much. I realize the ram actually lowers slightly at the very end of the stroke, and that is were I was setting my dies as stated above, instead of at the maximum extension of the ram.

[robg]

size the case, if it chambers easy your golden no need to stress the press or yourself.

[megasupermagnum]

Every die brand is different. It may seem obvious, but it seems too many skip reading the directions. I use Lee dies almost exclusively, and I set to cam over lightly. This normally bumps the shoulder back more than needed, but I have yet to have a die what I would consider excessive. Most Lee rifle dies seem to bump back to near maximum SAMMI specs. Normally I see .001"-.002" bump stated. While this is likely ideal for accuracy and case life, I've found that if you don't watch it, spring back can be a problem on these small amounts, especially with an expander ball die. Even sizing back .005"-.006", which is typical of a Lee die set to cam over, I have never had a case head separation.