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Thread: Setting up sizing dies and 'cam over'

  1. #1

    Setting up sizing dies and 'cam over'

    Hi Everyone. I'm new to reloading and just picking up my bits and pieces to get started, so apologies if this has been discussed before on a similar post. Just wondered what 'camming over' is in relation to setting up the sizing dies in the press. Is it necessary and why? I've read that some die manufacturers recommend it and some do not. Not sure so would like some advise please. Thanks.

  2. #2
    Quote Originally Posted by Bukshooter View Post
    Hi Everyone. I'm new to reloading and just picking up my bits and pieces to get started, so apologies if this has been discussed before on a similar post. Just wondered what 'camming over' is in relation to setting up the sizing dies in the press. Is it necessary and why? I've read that some die manufacturers recommend it and some do not. Not sure so would like some advise please. Thanks.
    If you take a look at your reloading press from the side you will see the linkage pins all align at the Top Dead Centre of the stroke, some presses allow linkage movement past TDC this 'over centre' movement enables the 'camming' effect.
    It is also a great way to damage / wear your press link pins and arms by being heavy handed in setting up your dies.

    Contact the shell holder means contact, you do not need to to feel a high resistance as you go over centre on the ram stroke, some people contact the die just enough to 'feel' the 'contact' so that psychologically they know that they have completed a stroke when the lever arm has stopped.

    I have a Lee press that physically is stopped from going over centre, it is perfectly usable and produces great ammo!
    My four other presses 2xRCBS, Corbin and C&H all have this 'camming effect' I avoid camming as I want my presses NOT to break or wear out!

    If you step back and think about the process of resizing a rifle cartridge, once the case is fully in the die (Full length sizing) and you have contact with your shell holder what does applying more pressure achieve? Are the dies and shell holder soft enough to allow you to push the case in some more? Are the dies dimensionally so unstable that you need to do this?
    Last edited by j0e_bl0ggs; 04-03-2012 at 07:45. Reason: addendum

  3. #3
    There are always going to be different views on camming over.

    My view is quite the opposite to Joe Bloggs. I do not see anything detrimental to the press in camming over. There is no additional wear area by having the press do this and I can confirm this, by never having had a press wear out in 30 years of reloading. My Lee press does not cam over and my RCBS does.
    (The only breakage with a press I have had, was with my Lee press and it was the linkage that failed. It was quickly repaired with parts easily available from USA).

    Provided the cases are properly lubed and the die correctly seated, there shouldn't be any undue resistance creating problems for the press.
    Camming over will maintain a better consistancy of sizing & bullet seating depth/cartridge overall length, as, once the ram has reached TDC, no amount of additional lever pressure will change anything, including the bullet seating depth because the ram has cammed over and is past TDC.
    Where the ram gets to TDC and does not cam over, as on a Lee press, additional lever pressure will make a difference to seating depth, perhaps shoving the bullet a few extra thou. into the case mouth/neck.

    Just depends how picky you want to be over your seating depth as to which method you view as more appropriate. For absolute cartridge OAL consistancy, I'd pick the RCBS camming over - every time.
    Last edited by deeangeo; 04-03-2012 at 10:15.
    Blaser K95 Luxus Kipplaufbüchse .25-06Rem. Zeiss 8x56, 110gn Nosler Accubond = Game Over!

  4. #4
    Needs a reply;

    Quote Originally Posted by deeangeo View Post
    There are always going to be different views on camming over.

    My view is quite the opposite to Joe Bloggs. I do not see anything detrimental to the press in camming over. There is no additional wear area by having the press do this and I can confirm this, by never having had a press wear out in 30 years of reloading. Then you do not know what to look for or on the other hand reload very little I have seen worn out presses in my 35+ years of reloading - Not Mine I hasten to add and I am an engineer so know what to look for (having made a few presses in my time).

    My Lee press does not cam over and my RCBS does.
    (The only breakage with a press I have had, was with my Lee press and it was the linkage that failed. too much stress because of over camming?
    It was quickly repaired with parts easily available from USA).

    Provided the cases are properly lubed and the die correctly seated, there shouldn't be any undue resistance creating problems for the press.
    Camming over will maintain a better consistancy of sizing & bullet seating depth/cartridge overall length, as, once the ram has reached TDC, no amount of additional lever pressure will change anything, including the bullet seating depth because the ram has cammed over and is past TDC.

    Flawed logic here you contradict yourself, "no amount of additional lever pressure will change anything" This is the point, no additional camming helps The amount of 'camming' is what does the damage to the press - tell you what, measure the frame deflection and correlate that to consistency of sizing and bullet seating.
    I mentioned in my reply about the psychological need for camming, thank you for pointing this out.


    Where the ram gets to TDC and does not cam over, as on a Lee press, additional lever pressure will make a difference to seating depth, perhaps shoving the bullet a few extra thou. into the case mouth/neck. Hmmm then your setup is poor, why would you want to try 'additional lever pressure' when the lever comes to a physical stop?

    Just depends how picky you want to be over your seating depth as to which method you view as more appropriate. For absolute cartridge OAL consistancy, I'd pick the RCBS camming over - every time.

    I am picky about my bullet seating depth but feel no need to abuse my presses.
    Consistency is about setup nothing at all to do with camming, unless you use it as a crutch to try and achieve it, it's just not necessary!.
    Hope this clears it up a little! And I hope no offence taken.
    Last edited by j0e_bl0ggs; 04-03-2012 at 14:03.

  5. #5
    Camming over doesn't change anything.With your dies set up properly, one is as accurate and consistent as the other. As was said; once the ram makes it to the top of the stroke, you're done, no matter what press you're using. I have seen some reloaders set their dies so that the shell holder mashes hard into the bottom of the die and they require a great deal of effort to get the ram to go past TDC. All it did was put wear and tear on the press. I have a Pacific 007 press that cams over. It is no more accurate than my RCBS A1 (heavy, pre Rockchucker) or my assorted Lee's and Lyman, which do not cam over. ~Muir
    Last edited by Muir; 04-03-2012 at 15:51.

  6. #6
    Firstly, no offence taken at all.

    My view is quite the opposite to Joe Bloggs. I do not see anything detrimental to the press in camming over. There is no additional wear area by having the press do this and I can confirm this, by never having had a press wear out in 30 years of reloading. Then you do not know what to look for or on the other hand reload very little I have seen worn out presses in my 35+ years of reloading - Not Mine I hasten to add and I am an engineer so know what to look for (having made a few presses in my time).
    I'm not an engineer, but happy to say I haven't had a press wear out either.

    My Lee press does not cam over and my RCBS does.
    (The only breakage with a press I have had, was with my Lee press and it was the linkage that failed. too much stress because of over camming? No, it was a breakage of a cast part that Lee on later models redesigned & made with pressed steel.
    It was quickly repaired with parts easily available from USA).

    Provided the cases are properly lubed and the die correctly seated, there shouldn't be any undue resistance creating problems for the press.
    Camming over will maintain a better consistancy of sizing & bullet seating depth/cartridge overall length, as, once the ram has reached TDC, no amount of additional lever pressure will change anything, including the bullet seating depth because the ram has cammed over and is past TDC.

    Flawed logic here you contradict yourself, "no amount of additional lever pressure will change anything" This is the point, no additional camming helps The amount of 'camming' is what does the damage to the press - tell you what, measure the frame deflection and correlate that to consistency of sizing and bullet seating.
    I mentioned in my reply about the psychological need for camming, thank you for pointing this out.

    Once the ram has cammed over & passed TDC there cannot be any further ramming pressure. All upward thrust has ended.There is no additional lever pressure.

    Where the ram gets to TDC and does not cam over, as on a Lee press, additional lever pressure will make a difference to seating depth, perhaps shoving the bullet a few extra thou. into the case mouth/neck. Hmmm then your setup is poor, why would you want to try 'additional lever pressure' when the lever comes to a physical stop?
    No I'm completely happy with my set up, however, inconsistant (Variable) lever pressure will indeed affect bullet seating depth, so, unless and until the user is careful and consistant in use of the lever/ram, ariations will easily occur. I agree, one should not need or want to exert any additional leverage when the ram is at the top of it's stroke, but especially for the inexperienced, it's easily done.

    Where the ram gets to TDC and does not cam over, as on a Lee press, additional lever pressure will make a difference to seating depth, perhaps shoving the bullet a few extra thou. into the case mouth/neck.

    Just depends how picky you want to be over your seating depth as to which method you view as more appropriate. For absolute cartridge OAL consistancy, I'd pick the RCBS camming over - every time.

    I am picky about my bullet seating depth but feel no need to abuse my presses.

    Consistency is about setup nothing at all to do with camming, unless you use it as a crutch to try and achieve it, it's just not necessary!.
    I didn't say I wasn't picky about the seating depth...or indeed the quality of ammunition I reload. However, I'm quite content my presses are not abused...I need them to keep making my ammunition & am sure they'll last me my lifetime.

    Muir makes a valid point in his post..either method is fine.
    Last edited by deeangeo; 04-03-2012 at 16:00.
    Blaser K95 Luxus Kipplaufbüchse .25-06Rem. Zeiss 8x56, 110gn Nosler Accubond = Game Over!

  7. #7
    JB/Deeangeo/Muir thanks for your posts and info, I think I've got my head around how the camming works. I havn't got my press yet (set my sights on the Redding ultramag soon) but speaking hypothetically....when you pull down the press lever, the ram travels on the upward stroke until it hits TDC (call this position A). At this point the lever hasn't stopped travelling and can go a little further until it stops, right?. Does the lever travel past the TDC position cause the ram to into a backward stroke? (call this position B)? If it does then at which position do you set your die against the shelholder, position A or B?

  8. #8
    I set mine at the full travel position, so cammed over on my RCBS.
    As other have said, no signs of wear and tear for me.

    As an engineer I see the camming action as a positive........
    If the lever cams over, provided you do actually cam it over each time the pressure used for each load will be the same.
    Yes the press will be under stress, but the same each time, and the press was designed to take it.
    With a press that does not cam over, just comes to a stop you can keep pressing and it will keep piling the pressure on, so unless you have
    a properly calibrated and certificated arm, each load you do will come under a different amount of pressure, does that matter, probably not (within reason).
    But with a cheaply made press, and a user who doesn't know his own strength something will break, usually the press.

    Neil.

    Cammed and camming, should really be "over centre" but didn't want to confuse anything.

  9. #9
    At TDC of the stroke, the ram cannot be raised further by the cam.
    At this position, the cam is at it's highest point under the ram and the shellholder should be 'gently kissing' the sizing die.
    The job is done.
    Once the cam moves beyond this highest point, the shellholder is coming off the die and all pressure is easing.

    Finding the correct position for the sizing die is a small matter of trial & error but tested easily with a correctly sized case sliding into the breech with the bolt locking down in a slick, easy movement.
    With the bullet seating die, the same principal applies (Die set up different of course), giving pretty consistant cartridge OAL's measuring using a comparator guage.
    Works for me.
    Last edited by deeangeo; 06-03-2012 at 07:09.
    Blaser K95 Luxus Kipplaufbüchse .25-06Rem. Zeiss 8x56, 110gn Nosler Accubond = Game Over!

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