Advice Needed on New Press.

[boomtube]

"Slop doesn't matter. It's just a matter of closing your eyes and clicking your heels together three times. Of course, holding your mouth just right doesn't hurt either. "


Win, from your "tongue in cheek" response I assume you disagree that a modest amount of looseness in a press ram fit IS determentail? If so, I would ask why/how?

Seems IF a tight ram-to-press fit were in fact helpful to accuracy the serious BR croud would be using rigidly fitted presses and wrench installed dies; they don't. Instead, they use un-threaded "hand dies" and push their cases in and out of them with light arbor presses sitting loosely on the bench top.

Are they be wrong to work that way; would they do better if they used tight cast iron presses and firmly installed dies as some of us try hard to do? Or, might they be right and allowing their cases to freely enter the dies with NO external interferience - meaning a lot of "slop" - actually IS a good way to achieve more concentrict, better aligned ammo? And, if so and within rational limits, might the same broad principle for a floating alignment of cases in the dies also be helpful for the rest of us?

 

[Winchester 69]

I reiterate:

When the ram is aligned with the die and held in a tight bore, all of its force is likewise directed. In a loose bore, the ram will want to misalign when it meets resistance, simply as a tendency to reduce the resistance. Oppose two fingers linearly and push them into one another. As the fingers deflect off-axis, resistance is reduced. The ram wants to do the same thing. Let's consider that the ram is cocked in its bore. Realize that the force into the die is reduced somewhat. The ram's full force is on the axis of the ram. Think of the ram and its force as the hypotenuse of a right triangle. The leg of the triangle that is aligned with the die represents by its length the force being transmitted into the die on its axis. The other leg of the triangle represents by its length the amount of lateral force that is being resisted by the die, and any brass that is in it, at a right angle to the die. That is the force that is deleterious to to the straightness and otherwise dimensional integrity of a shell case. The greater the deflection, the larger the proportion of the ram's force that is transmitted laterally.

Compliance in the shell holder allows the brass to align itself in the die, but the lateral force remains.

Your description of the functioning of hand-dies doesn't concur with that in the Precision Reloading & Shooting Handbook, 10th Ed. (Gravett & Sinclair).

 

[Chas1]

Is it possible the BR guys worry less about slop since in most cases their not sizing big cases like the 300 rum where more force is needed as opposed to smaller cases so less force...less deflection??

 

[flashhole]

Flashole, if you're still reading this, I just gotta ask, why two UltraMag presses?

I like working with a single stage press and I will set up multiple presses to do individual steps w/o having to change dies. I also do a fair amount of resizing and it's real handy to have different dies set up to finish a case completely in lieu of batch processing. The Ultramags are really good for this. I bought both of them on eBay back when you could get a good deal on eBay and people weren't paying more money for used reloading equipment than you have to pay for new.

 

[Winchester 69]

Is it possible the BR guys worry less about slop since in most cases their not sizing big cases like the 300 rum where more force is needed as opposed to smaller cases so less force...less deflection??

Almost. Less ram force OR less deflection --> less lateral force. If the brass isn't affected, fine.

How much slop is there in a Harrell or Sinclair press?

 

[Chas1]

Winchester 69, How much slop is there in a Harrell or Sinclair press? I have no clue. Just asking the question I did cause I don't know and was wondering.

 

[Winchester 69]

Winchester 69, How much slop is there in a Harrell or Sinclair press? I have no clue. Just asking the question I did cause I don't know and was wondering.

I've never laid eyes on one either, but others imply that these presses aren't tight as they're preferred by BR'ers. I can relate what Zediker has had to say about the Harrell:

The ram is centered, straight, and has very close fit (just enough for the ram to stroke).

What I've said before is that compliance in the ram/bore is not an appropriate means of compensating for a misaligned frame.
.

 

[Clark]

I bought a Forster Co-ax press a couple years ago.

My other presses are jut gathering dust now:
RCBS Rockchucker press
RCBS partner press
Lee reloader presses
Dillon 550B progressive press
Lyman All American press

 

[Moman]

Just an update on the press situation. I spent quite a bit of time looking at the press and besides the lateral ram movement, the ram also rotates counterclockwise when at the top of its stroke. I found a lot of movement at the toggle block and bow washers as well as the right support arm. I'm pretty sure this is what is leading to excessive runout, especially the ram rotation.

I called RCBS and explained the problem. They are sending out a new ram, toggle block, bow washers, and pins for toggle block and support arms. You gotta love a company like that.

 

[Chas1]

Sounds like some good customer support on the part of RCBS. Let us know how it works out for you.

 

[boomtube]

I reiterate: ...In a loose bore, the ram will want to misalign when it meets resistance, simply as a tendency to reduce the resistance. ... Think of the ram and its force as the hypotenuse of a right triangle. The leg of the triangle that is aligned with the die represents by its length the force being transmitted into the die on its axis. The other leg of the triangle represents by its length the amount of lateral force that is being resisted by the die, and any brass that is in it, at a right angle to the die. ...The greater the deflection, the larger the proportion of the ram's force that is transmitted laterally.

Compliance in the shell holder allows the brass to align itself in the die, but the lateral force remains."

Okay, let me go through it briefly.

All you say is true but you omit one critical factor - the leg of the triangle you mention is so close to nothing at the point of ram travel as to mean nothing. to the cases. At the point the side force comes into resistance the stiffness of the case is easily able to withstand that tiny residual lateral force from the very slightly off-set toggle. Ergo, ram looslness is largely irrelivant to acccuracy.

 

[Winchester 69]

The deviation in the business end of the ram increases proportionally to the amount of extension. What the brass experiences is determined by the force exerted by the user and the amount of deviation. At what point does it not matter?

 

[Moman]

Sounds like some good customer support on the part of RCBS. Let us know how it works out for you.

Yeah, hopefully this will take care of it. If not, I have a Co-Ax on backorder but don't think I'll need it.

I understand what you guys are saying for the most part. The more I studied the Co-Ax type press, maybe a little play is o.k. My biggest concern with the ram is that when the press handle is lowered, there is excessive play in the toggle that allows the ram to physically rotate counterclockwise when viewed from the top. That can't be good. As far as the lateral play in the ram, I'm not sure how much that is contributing. When I mentioned it to RCBS, he was concerned enough about it to send me a new ram.

Anyway, the parts are on the way and I'm hopeful this will take care of it.

 

[Clark]

Thread about RCBS Partner pressed with loose rams:
Wanting to Upgrade Reloading Press for Live Varmint Rifles - Benchrest Central Forums

One of the best shooters in the Gulf Coast Region of the NBRSA, Jackie Schmidt, reloads with a rack of RCBS Partner presses that have had their rams turned down to produce more radial clearance, slop if you will

Another thread about RCBS Partner pressed with loose rams:
Brunos Press - Benchrest Central Forums