K&M and 21st Century arbor press

[jimcasey01]

Need some advice on the differences in use re: K&M Arbor Press with Force Measurement and the 21st Century Hydro Bullet Seater. I know one uses hydraulics and the other springs and washers. In use, can someone explain the advantages one has over the other. Thanks for your help in advance, Jim.

 

[TonyR]

I've had both and am using the 21st Century now. Both do the job well. The 21st Century is much easier to change for different cartridge lengths. For example, I use mine for a Dasher and a 280AI which require different heights on the column. The K&M is easier if you plan to travel and want a press that breaks down. It disassembles with an Allen wrench and lays flat. Can't do that with the 21st Century because of the plumbing.

 

[Jeff Von Rosenberg]

The 21st century actually gives you psi seating pressure. Had both don't have K&M any longer!

 

[jlow]

Well, apart from what TonyR already said, there is a price difference - $250 for the 21st Century and $170 for the K&M. For the K&M price, you don’t get a dial indicator but if you are like me and have a few lying around, it ends up being cheaper.

For the job they do, I don’t think there is really any difference. As to reading, your dial indicator will give you those numbers so as they say “no difference..” since the numbers are not so important as any potential difference between rounds.

 

[DeltaBravo]

Okay, I'm considering upgrading to one of them. What, exactly, is the importance or relevance to 100/200 yard benchrest shooting? How much, if any, improvement can I expect to see accuracy-wise?

I currently use the 21st Century arbor press (old model) and cannot really 'feel' that much difference other than "easy" "less easy" - so spending another 200+ bucks has to have some really great value on the paper.

Thanks!

Dennis

 

[TonyR]

I only shoot F-Class and uniform neck tension is very important. As jlow said, the actual value doesn't seem as important as having all rounds close to the same, so either tool gives a workable value. Uniform seating force seems to mirror uniform neck tension at least in my reloading process. I found the K&M very useful when I was trying to improve my reloading process. Now I use the 21st to check for my mistakes.

 

[jlow]

No expert in this but I will give you my take on this “seating force” or what I call “entry force”.

What I think happens is when you start pulling that handle down, force is applied via the bullet on the case. The case mouth starts to open up and at some point, the bullet slips in. What you are looking for is a couple of things. One is at which force level does the case mouth open and let that bullet to slip in and two, how smooth does all this goes down.

When the bullet slips in, things should goes fast and the force goes quickly real high as you are now just cranking down on the handle and not the bullet. So what you should feel in this overall process is ideally a slow and even build up of back pressure and then it jumps. Where it jumps is the number you are looking for.

This seems pretty simple but I think a lot of factors plays into it. For example:

The neck opening, how wide is it (i.e. neck tension)? How thick is the brass at the neck? How concentric is the hole because it affect whether the bullet is entering straight (easier) or cock eyed (harder). How good is your seater die because it affects the same thing. How soft is the metal at the neck (i.e. degree of work hardening)? How smooth and chamfer is the opening as if it is not and it catches or scratch the bullet, you will know it.

Of course, the shape and concentricity of the part of the bullet that enters the neck affects things. How smooth it is? What is its diameter?

So all of this gives you one number and one feel and if you are able to properly control all of the above, what you will get is a consistent “entry force” number and overall feel.

 

[jimcasey01]

I wish to thank all who responded with their input and wisdom.
Jim