Free Float Press Shellholder

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Re: Free Float Press Shellholder

Postby buckeye43210 » 12 May 2018 10

Fyodor wrote:Yes, but the spring clip is insignificantly weak in comparison to the ram force. So if it isn't concentric, and it will free float to the correct position with the O-ring, it will free float with the spring clip, too. The clip isn't limiting the range of movement. it just gives a little more resistance.


I won't go through the math at this time, but the force of the spring clip is orthogonal to the force of the ram. Therefore, the horizontal force of the spring clip is significant relative the horizontal component of the vertical ram force...
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Re: Free Float Press Shellholder

Postby Macd » 13 May 2018 12

Geewiz buckeye, now my head hurts. :p

My take, and I may be wrong, is if there is sufficient play in the shell holder's fit in relation to the slot in the ram it should be able to orient to the centre and the angle of the die. In other words if the die is not perpendicular to the slot the case should move the shell holder to the proper orientation as it enters the die. The fly in the ointment, in my experience, is often the shell holder is a tight fit and is limited in its ability to reorient. This exacerbates any other misalignment such as die axis to ram axis or the slot or die base to the surface of the shell holder. Add a tight fitting case rim and things just get worse. I believe the spring should not grip the shell holder but just loosely keep it in the ram slot. As soon as the play that allows self adjustment is removed from the equation then alignment tolerances become critical. This makes manufacturing much more difficult and expensive.
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Re: Free Float Press Shellholder

Postby Fyodor » 13 May 2018 12

buckeye43210 wrote:Therefore, the horizontal force of the spring clip is significant relative the horizontal component of the vertical ram force...


You forgot, that if it was like that, even an air bearing would be immovable, because the vertical ram movement has no horizontal component at all.

But there is the shell that has some angular degree of freedom. A slightly canted case acts as a tilted plane type lever with a brutal gear ratio. That vertical component gets translated to a manyfold horizontal force.
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Re: Free Float Press Shellholder

Postby EdgeOfEden » 19 May 2018 17

While interesting to read, I'm not exactly sure why this is being debated when there is already demonstrative evidence that a free floating shell holder aids in reduced bullet run out while seating. How many measurements have to be done before we are convinced? It's like debating on whether or not the Bernoulli Principle can explain why an airplane flies, when in fact it flies. If the Bernoulli Principle is false, the plane doesn't go up. As a layman, I can be happy knowing the airplane will fly even if I don't understand why. Likewise I don't have to understand the various geometric forces on the case and shell holder to know that a free floating shell holder does indeed lower bullet run out. A press that has perfect alignment likely won't benefit much, but if the ram axis is slightly off (for whatever reason), a free floating shell holder will make a difference.

Why do you think so many spend big bucks for the Forster Co-Ax and some are now thrilled to have the less expensive MEC Marksman? Again, for the average shooter, this difference will likely mean nothing, but for the long distance shooter every advantage matters. I'm content just to add an O-Ring to my Lee Classic Cast Breech Lock when I start loading for my 6.5 Creedmoor bolt action. :)
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