A plug for the K&M arbor press with force measurement tool.

[jlow]

Been using this now for a couple of years and generally like it. Today I had an interesting experience using it. I have been reloading my 223 rounds with Nosler 77 grain CC bullets in Lapua neck turned/annealed brass (3x fired) but ran out of bullets after the last outing and so had to open a new box. After weight sorting the bullets I started to reload for my next outing.

As soon as I started to seat the bullets (K&M press with a Wilson seater), I noticed that there was a different in the seating force. My normal average seating force is around 60 lb (61 lbs ES 11 lb N=27). This time it was more like 50 lb (50 lb, EX 15 lb, N=22).

I measured 7 bullets from each of the two lots (had a few left which I did not mix with the new stuff) with my Mito digital micrometer and found that the old lot had an average diameter of 0.22408” (SDEV = 0.00007”) whereas the new bullet lot had an average diameter of 0.22380” (SDEV = 0.00008”), not complaining since there is really only a 0.00029” difference between the two which obviously came out of a different machine. Still I was pleasantly surprised to see how sensitive the K&M was in its ability to pick up such slight difference.

 

[mikecr]

Was there any lube/wax on the new bullet jackets?
Since you're comparing friction really, it seems more likely direct than indirect for such a large change.

 

[artbosco]

Tried it a few years ago. Didn't like it. Sent it back. Use the standard K&M arbor.

 

[tenring]

Tried it a few years ago. Didn't like it. Sent it back. Use the standard K&M arbor.

I did the same thing. Too inconsistent

 

[Erik Cortina]

Tried it a few years ago. Didn't like it. Sent it back. Use the standard K&M arbor.

I did the same thing. Too inconsistent

Was it the press or your brass?

 

[jlow]

Mikecr – No lube/wax on the new bullet jackets. I don’t think friction is the only thing the K&M press is measuring. The proper use of the tool entail the measuring of the pressure point just when it jumps from static to actual full seating of the bullet. The Nosler like the SMK of the same weight is a boat tail bullet and I am pretty sure that this would be the point after the bullet starts to expand the neck and just when it gains full entry into the neck i.e. just before the bullet rapidly slides down the neck. So although friction plays a part, a big part involves the pressure required to expand the neck fully to the diameter of the bullet bearing surface.

I can understand why a lot of people give up on the press since that was also my initial impression i.e. it is hard to use and difficult to like. However, once you figured it out (and of course assuming as Erik pointed out you can reproducible brass prep), it is quite easy and reproducible and as mentioned earlier, quite sensitive to slight changes in friction, neck softness, and bullet/neck diameter.

 

[mikecr]

quite sensitive to slight changes in friction, neck softness, and bullet/neck diameter.

It is friction you're measuring, the force in overcoming it, with all else inferred out of this(given that they affect it). Not that there is anything wrong with it, just that you need to understand that anything affecting friction to bullet seating affects your readings. With this there can be false indications w/regard to inferred neck tension(bullet grip).

I use a similar system. But mine's electronic, using a FlexiForce sensor above expander mandrels(built into Sinclair's expander die). http://www.tekscan.com/flexible-force-sensors
This eliminates bullets from expansion measure, which is desirable, because bullets make terrible expanders.
Mandrels are consistent in shape and hard and friction is less variable with them. I also pre-expand necks prior to seating anyway.

It would be hard to see, but maybe the transition between boat tail length and bearing has changed between bullets. This could increase friction in seating.
Or, maybe you are seeing ~.0003 bearing difference. I'm just trying to rule out other possibilities.

 

[1shot]

To all posters on this thread, this is about as perfect a post/response I have read in 6-7 years. I say this because I was going to contact K&M and ask to exchange my current standard arbor press and upgrade to the high $$$ model tomorrow. Now I'm re-thinking the entire game plan because of lot of very good, useable, logical data from not just one but several posters. On one side of the coin, my post has nothing to do with the OP or his subject., however on the other side, there is a wealth of USEABLE knowledge freely given by several posters.
Well done gentlemen.
Lloyd

 

[jlow]

Mikecr - I agree friction is part of it but if you don’t think the other factors are involved, image seating a flat based bullet instead of a boat tail and the difference in feel and forces involved.

I don’t think anyone would say that this is a direct measure of neck tension. However some of the same factors I listed are in fact directly and indirecty involved in neck tension. For example, the opening of the mouth of the neck which is of course not involved in the release of the bullet. However, since it is affected by how soft the brass is i.e. degree of annealing and how smooth the two surfaces are, the same factors are also involved in neck tension.

Your system is indeed more pure in measuring the neck without the influence of the bullet since you use a mandrel but keep in mind that when you finally seat the bullet and if the bullet has differences in diameter/smoothness you cannot take into account it’s influence on the final neck tension. What you are doing is in fact taking the system apart and measuring one of them independently - that is good. However, since you are not doing the same with the other part i.e. the bullet, you are missing half of it.

1shot – glad to be of help.

 

[6BRinNZ]

Jlow - did you notice that the seating depth was less with the reduced force?

 

[jlow]

No, from previous experience using the Wilson and other brass but the same bullet, the slight change (or even significant differences) in seating force does not affect seating depth. The Wilson is very consistent (within 1 thousands) and remains this way. The key is of course a steady movement all the way as you pull down the handle.

However, the new bullets did initially seated deeper but not because of the seating force but I think because of slight difference in the shape of the ojive. If I remember correctly, the bullets seated 4 thousands deeper.

 

[6BRinNZ]

No, from previous experience using the Wilson and other brass but the same bullet, the slight change (or even significant differences) in seating force does not affect seating depth. The Wilson is very consistent (within 1 thousands) and remains this way. The key is of course a steady movement all the way as you pull down the handle.

However, the new bullets did initially seated deeper but not because of the seating force but I think because of slight difference in the shape of the ojive. If I remember correctly, the bullets seated 4 thousands deeper.

Thanks. I would have thought that a significant force change would slide the bullet further into the seating stem and thus it would finish at a different depth (higher). Where I detect the extra force I don't notice this occurring as a constant, so was curious what the results were, where detailed force and depth measurements were taken.

 

[jlow]

OK, I see where you are coming from, but unfortunately I did not see this.

As mentioned in the last post, these new bullets seated with less force but they actually ended up seating 4 thousands deeper which I think is in the wrong direction. My guess is what you theorized might be true but at least in this case, the difference in ogive shape was significant enough and had a greater influence that I could not detect the other effect.

FWIW, these new bullets also had a different bearing surface length. This is somewhat expected since their ogive shape is likely slightly different - they were about 20 thousands shorter 0.4900" vs. 0.5096".