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Thread: Press cam over

  1. #1
    Boolit Master Bazoo's Avatar
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    Press cam over

    I have a C frame Lyman spartan, it cams over instead of having a solid stop. I always set my dies so they just barely miss the shell holder and cams over. I've not had any problems.

    Is there any disadvantages to the cam over design that im not getting?

    ~Bazoo

  2. #2
    Boolit Master
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    I've never considered it a problem. I use my 46yr old SPARTAN as a secondary press & I size/decap on it. Use it sometimes with the Lee bullet dies. Just FLIP the handle around to raise the ram on the upstroke. Unbolt the press, reboot it upside down and fix a fat piece of hose to drop the bullets into a bucket at my feet.
    That press is a faithful old friend.
    Happiness is a Warm GUN & more ammo to shoot in it.

  3. #3
    Boolit Master
    mdi's Avatar
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    Never saw a reason nor a need to make my press go "over top dead center". None of my presses will and the one that might, uses the shell holder as a dead stop for F/L sizing...
    My Anchor is holding fast!

  4. #4
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    I don't now, but I have in the past. Do what works for you.

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  5. #5
    Boolit Man metricmonkeywrench's Avatar
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    Haven't really bought into to the cam over school of thought. It takes some tinkering but I set my dies so that when the ram is fully raised and with a shell in the die to get no gap between the shell holder and die. This takes up all the slack in the press and linkages. It is verified with dental floss as a check. I have done this for both rifle and pistol with no issue.

    There are some carbide dies that do not recomend camming over as it may loosen or crack the insert.
    Last edited by metricmonkeywrench; 05-13-2018 at 05:13 PM.

  6. #6
    Boolit Master

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    I set up my dies to bump the shoulder of my bottleneck cases 0.001-0.0015" whether the press cams over or not is irrelevant to me. On some dies, that does occur, but it is rare. On pistols, I dont allow carbide dies to make hard contact with the shellholder at all
    Last edited by BK7saum; 05-13-2018 at 04:45 PM.

  7. #7
    Boolit Master DonMountain's Avatar
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    If you don't have a cam-over type of linkage on a press, how would you ever know if you pushed the handle down far enough to set the headspace dimension correct for your rifle? It seems that if you set the die to bottom out on the shellholder, how would you "feel" this point if you happen to have a shell casing that was fired in another rifle? It would be like trying to seat primers by feel instead of a precision set stop for depth. Feel just doesn't get you there precisely. The cam-over point designed into all of the presses that I own is there for a precision point that is used to set your dies appropriately without having to rely on "feel" to get you to the bottom of the stroke.

  8. #8
    Boolit Master Bazoo's Avatar
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    Thanks for the replies. DonMountain, I hadnt thought of that.

  9. #9
    Boolit Man metricmonkeywrench's Avatar
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    Cant speak to other presses, I have a RCBS RC-II and there is a positive stop on the linkage when the ram is in the full up position. There may be a little overtravel on handle but to use an automotive term the ram reaches Top Dead Center and can travel no further up unburdoned. The die is now screwed in until contact is made with the shell holder. A case is inserted and run up into the die. Clearance between the shell holder an die is checked and the die adjusted accordingly to get 0 gap between the shell holder and die. This should accont for the slop in the linkage and any spring in the press but not put any stress on a carbide ringin pistol dies. Thie die is now set and locked down for full length sizing for either pistol or rifle.

    If the goal is neck sizing only or a specific shoulder setback for necked brass then the process is diffrent.

    Either way there really is no feel needed once the dies are set just run to the stop, which should give you a repeatable case dimension which is the goal. The feel I'm looking for are soft sizing which may indicate cracked brass or signs of lube problems on bottle necked brass.

    Is there something I'm missing if I don't put extra stress on my dies ir press?

  10. #10
    Boolit Master DonMountain's Avatar
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    Quote Originally Posted by metricmonkeywrench View Post
    Cant speak to other presses, I have a RCBS RC-II and there is a positive stop on the linkage when the ram is in the full up position. There may be a little overtravel on handle but to use an automotive term the ram reaches Top Dead Center and can travel no further up unburdoned.

    Is there something I'm missing if I don't put extra stress on my dies ir press?
    I have an RCBS AmmoMaster press and at first look I thought that maybe it had a mechanical stop also. But with a much closer look at the linkage and how its designed it also "cams over", although it is almost indistinguishable from just hitting a mechanical stop. The "cam over" only lowers the ram by a few thousandths of an inch where my Hornady-Pacific presses appear to be much more noticeable at several thousandths of an inch. The "little overtravel" you mention is the cam-over occurring before hitting the mechanical stop.
    Last edited by DonMountain; 05-15-2018 at 03:14 PM.

  11. #11
    Boolit Master
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    Bazoo,

    The disadvantage as I see it is the high likelihood of over sizing your brass which in turn leads to short brass life.

    RCBS, Hornady and lee along with possibly others instruct a person to set a full length sizing die down far enough for the press ram to cam over center at the top of the stroke.

    Hornady, with the addition of a "foot note" with their instructions seems to be the only one that has a clue as per the realities of life and manufacturing tolerances.

    They indicate that in some rifles/actions, settimng the full length dies as instruction can lead to excess head space. As such, that will lead to shorter case life and less hand load consistency.

    With a platform such as a semi-auto, especially with something like an AR where 100% reliability is very important, brass life is secondary to reliability.

    However with most bolt action or single shot rifles, the dies should be adjusted so that brass fired in YOUR rifle is sized the minimum amount needed to allow that brass to smoothly rechamber in YOUR chamber.

    This would not be an issue in a perfect world without the need for manufacturing tolerances, but in our real world and in most situations it is best to set your dies for your rifles chamber, sizing the minimum amount possible.

    It is possible/likely that if you owned more then one rifle chambered for the same cartridge the best way would be to have a full length sizing die dedicated to each chamber.

    This doesn't mean that you can't follow the die manufactures instructions and make usable ammo, just that doing so is MANY times not optimum for best brass life and load consistency.

    Crusty Deary Ol'Coot

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BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
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