Home Forums Reloading Big Game Rifles Die adjustment and "cam rollover"

I think I have been using my press "wrong". Can someone splain how to adjust the "cam rollover snap" that should happen when sizing? I have not been utilizing that final rollover, and feel that my resizing has been a bit inconsistent because of it.

How much "snap" should be felt on that last bit of handle push, without causing the press frame to flex?

I have a older, made in US RCBS RC press. I was partial FL resizing some .358 brass last night, and realized what I was missing by not having that positive contact that rolling the cam brings. I think I am now doing it right. I am not mistaken on using that rollover, am I?

Another question: should that cam rollover be used to seat bullets too?

Sakoluvr,

I'd let the rifle tell you whether to "cam over" or not. By cam over I think you mean shellholder contacting the base of the die and then turning the die in some more. I've got a Simplex O press which is a clone of the RCBS RC. Now when you are FLS the press does flex and by turning in the die some more you are eliminating this flex. For most of my rifles I do not need to cam over to get the brass to fit the chamber reliably (but I do push the lever to the end of the stroke and technically it does cam over). In a Browning BLR .270 I definitely do need to "cam over" and by a fair bit.

But for certain dies eg Lee Collet you never want to cam over or you can damage the die.

For seating yes you cam over because that is the end of the stroke in that kind of press but you do not mash the base of the die into the shellholder which is what you do when you FLS (well sometimes). I put a sized case in the press and put the ram all the way up. Then screw in the seater die with the bullet seat stem screwed most of the way up.I screw the die in till I feel it touches the neck, then back it off 1/2 a turn. Of course if you want to crimp then its different but the dies usually come with instructions for that.

Hope this helps.

Hey here is Australia there are lots of Sako Lovers too! Got one in every length now.

Regards
JohnT

Not all rifles require the "rollover", let your rifle tell you how much sizing you need or measure it with any of the available tools. I load for over thirty rifles and don't use any type of "rollover" during sizing. I can't see any reason you would need that for seating bullets. Regular seating dies with the built-in crimper would present a real problem and the competition type seaters are not designed for any "rollover".Rick.

Thanks you guys. I thought the rollover was needed when FL sizing. I was loading for my BLR .358. I had neck sized only for the first 2 firings with zero problems, but realized I could not get away with NK sizing only for a 3rd firing in that lever action. The cases were pretty sticky when I tried a few rounds, so I decided to partial FL resize. I used Redding's competition shell holder to allow for the partial resize, instead of backing the die out. I allowed for some cam rollover, which I have not been doing before. I guess it is not a necessary function. BTW, the partial FL resize did the trick, and when I measured cartridge head space, it was within spec.

When I need the cam-over for FL sizing (not always, as the guys above have said), I adjust it using the press handle.

I'll screw the die in until it touches the shellholder on a fully raised ram. Now I raise the end of the press handle a half-inch and hold it there (I'll use a yardstick on the floor as both a measure and a rest by pinching it against the press handle.) Now screw the die in until it touches the shellholder again. Lock the die ring.

In use, you'll feel the lubed case go into the die until the shellholder touches the die, and then there'll be that last half-inch of handle travel that goes up and over top dead center with a kind of dull bump. Perfect.

Thanks Rocky. As an aside, I used Hornady One Shot for the first time last night. I like it! Lots less handling time of brass. It wipes off real easy and clean with a paper towel too.

Any time I used the "cam over" full legnth sizing it caused problems with excessive head spacing.

One cannot say "cam-rollover" causes excess headspace. A certain rifle may have a short or long chamber, or for that matter I have had fl dies that were too long. As others have said you need to size to fit the chamber. On the fl dies that were too long I simple ground a small amout off the bottom of the fl die so it allowed me to set the shoulders back & correct the headspace for that chamber.

Well that's obvious. I don't think PDS was saying that, just when "he" cam'd over with "his" dies, it caused excessive headspeace in his rifles. I've never ground down the FL dies but I have ground down a shellholder or two.

IMO, The best way to adjust a FL or Body die is just get the Hornady/Stoney Point Headspace Comparator thingy w/ inserts. Take a virgin case , fire it and measure it. Subtract .002" and that's where you want it sized. My .02...

OK, now I know where I read about "having the press linkage "pop over center". I just dug out an old book by George C. Nonte, Jr.


He says to turn the resizing die another 1/8 turn after it makes solid contact with the ram. The shell holder should bump the die, and you should feel the press linkage pop. He goes on to say that this places the press frame in tension, and eliminates the possibility of it stretching under the load of resizing and thus keeps the case from going all the way into the die.


More comments? Mule Deer, how about it?

It's not an absolute. The idea when you're sizing brass is to get it sized the way you want it. This is not always achieved by getting the case all the way into the die. Given three rifles chambered to the same cartridge, the same sizing die may need three different adjustments to achieve the same type of fit for the brass in the three different chambers.

mathman

A few decades ago it was de rigeur to cam-over when full length sizing. It's not necessary--even less so with partial full length resizing or neck sizing.......

Casey

I can't imagine a worse way to set-up on average....

Why cam over, though?

I picked up a .270 WSM last Fall. After shooting it a number of times I found the cases becoming increasingly more difficult to chamber probably due to the relatively sharp shoulder.
Eventually in order to not be throwing out perfectly good cases I set up my FL die with more and more rollover. I now seem to have found a setting that allows the cases to chamber easily so the reloads can be used for hunting without concern.
This is the only cartridge I have ever reloaded for which required this kind of set up in order to work smoothly.
Based on my experience I would suggest using cam rollover only as a last resort if your rifle shows it needs it.

My model 700 .270 wont chamber most factory rounds. I started reloading and quickly discovered that I had to turn the die 1/4 turn past the point of contact in order to fit the chamber. I was told that was the difference between full length and partial re sizing. TVC15

This is from his article on the reloading part of this site, it might help:

"If you've got a tight chamber, fired brass may not affect accuracy, but most of the time, fired brass headspaces more precisely and has straighter necks. After "fire-forming" brass in your rifle's chamber, set the dies so that the action closes on a sized case with just a slight amount of extra effort. Many methods can be used, including specialized tools such as Redding's "Instant Indicator" headspace comparator, or blacking the shoulder area with match or candle smoke. I usually just run the die into the press, with the ram up, until the die butts against the shell holder. Then I back it off half a turn and resize a fired case. Normally this lightly-sized case takes some effort to chamber, so I keep turning the die in, perhaps 1/20th of a turn at a time, and resizing the same case until the desired slight "crush fit" results.

I agree wholeheartedly with that excerpt. It isn't often that you NEED to size cases absolutely as much as the press/die allows - usually it works better to do as described. But if you keep adjusting and adjusting down and the sized case STILL won't go into the chamber without excess effort, then the cam-rollover technique is the penultimate step to take. If that still doesn't size enough, you'll have to grind something shorter or clean the chamber out a bit.

To the question asked above, cam rollover was more often needed several decades ago when press weren't as sturdy (and/or die tolerances weren't as good) as they are today. The press actually stretched from the force of shoving the case into the die. So to GET the case fully in, you had to adjust the press opening to be a whisker too small when it wasn't under load. Hence, the "die contact plus a bit" adjustment.

Point taken, however there are some of the same "less robust" presses in existence today as there were 30 years ago. Likewise, their are some of the same "heavy duty" presses in existence today as their were 30 years ago.

I think mildly snapping the cam over provides a positive repeatable stop to the ram. Obviously if you are partial FL sizing, this cannot be done unless you are using Redding competition shell holders, which vary in thickness thus "allowing" the ram to be raised further toward the die as the thickness of the shell holder decreases. I think they are a good addition to reloading tools because the die never needs to get adjusted, and the level of partial resizing is kinda exact, and can be tried in increments until the exact shoulder bump needed is achieved without touching the die (or buying micrometer adjustment FL dies).

Still learning here, and love talking out loud to you more experienced reloaders. I really appreciate everyone's feedback.