Reloading press question

[Kerf]

Rather than hijack and distract in another thread topic, here’s a new thread.
I came across this quote from RC: “I would bet your sizing die is not screwed down all the way and 'bumping' over center at full ram travel.If it isn't, you are not pushing the shoulder back where it belongs.”

So, is “bumping over” normal operation; should it occur on every stroke?
I had a much used press that began “bumping over” and I assumed the press was worn out from use or abuse. (I think it was the only reloading press within a half days drive and there was always someone in there using it. Probably a couple hundred K on it.) I thought the pins in the linkage were shot or the head was sprung and stretching with each resizing. I never trusted that press after it began doing that and eventually used that as an excuse to buy a new press, or three.
I don’t think the presses I’m now using are bumping over, not really sure.

kerf

 

[jwrowland77]

I know the press I have, when the resizing die is kissing the shell holder, I can lower my handle, and it'll stop when it touches it, then when I give just the slightest pressure, the handle seems to break over a certain point, and I know I'm getting a full resize.

 

[Sunray]

"...is “bumping over” normal..." It's not really a bump. It's when the ram is all the way up, if you put it up a bit more, the ram comes back down. S'ok. If there's a noise, the die needs a slight adjustment up because the die is thumping the shell holder. The shell holder should just kiss the bottom of the die with the ram all the way up.
"...assumed the press was..." It's very difficult to damage modern reloading kit. If it's RCBS kit, they'll fix any of their kit regardless of who bought it new with a phone call. Their life time warranty is on the equipment, period.

 

[rcmodel]

Let me chime in.

Yes, bumping over is common in some brands of presses, (RCBS Rock-Chucker for instance) and it is necessary to get full-length sizing of bottle-neck rifle cases.

It is not a matter of the ram going all the way to the top, and starting back down though.
It is the point when the linkage snaps into prefect vertical alignment and is exerting full 100% force to the ram.

Other brands of presses use a positive handle stop, and do not 'bump over'.

But they still need to 'bump' at full travel to FL size bottle neck rifle calibers.

Otherwise, linkage pin slack, and frame & linkage stretch & compression will not allow the shoulder to be pushed back where it came from.

If you just screw the sizing die down to contact the shell holder with no load on it, the press frame flex will open up the gap when under full pressure sizing a case.

Carbide handgun dies should not be adjusted that tight, as it is possible to crack or loosen the carbide insert in the die.

rc

 

[Kerf]

I think rc nailed it… Who would’a guessed?
“If you just screw the sizing die down to contact the shell holder with no load on it, the press frame flex will open up the gap when under full pressure sizing a case.”
Thinking back, that press (Pacific Tool) was used exclusively for straight walled pistol cases until I started reloading 30-06 with military surplus cases, and that was probably when I started noticing the bump over situation. That military brass was really heavy and stout, 4-6grs heavier than commercial, and that was probably what was causing the bump over.
Thanks for all the helpful advise, everyone. Thought maybe I was doing it wrong.
kerf