K & M Arbor press with "seating force measurement gauge"

[BigKev]

Gentlemen,

Having read several posts regarding the use of a K & M Arbor press with the "seating force measuring gauge" I have a question. Is there an "optimal" measurement that one is looking for ?? meaning have those of you that have one and or have used one to further fine tune your loads is there a "specific" seating measurement / pressure you're looking for ?? I realize that each gun is different with regards to neck tension or does one simply use the same set up that's been utilized in a standard press and then translate it to the K&M's readings in an attempt to hold "group" tolerances to what was found ??

 

[normmatzen]

Just got my force senser up and running.
Seated the first 35 rounds with it and found that with the bushing die I use for 6BRX, The initial "start" pressure is 20-25 lbs for 2/3 of the cases and 15 lbs for the remaining 1/3.
I shot the 20-25 lbs group and the es improved 10% and the SD 14%.

I will try the small group later.
I also noticed the final seating pressure was 125lbs for all bullets. I wasn't expecting this?

Now, I prep my cases by ultrasonically cleaning so there is nothing on the neck interior but shiny brass.

I will continue to research this issue! I will try a looser bushing as well as a group sized with a LEE custom collett die.

 

[brian427cobra]

First off I got a elcheapo Habour Frieght Dial on mine, 45 pounds is my majic number.

 

[searcher]

Using the K&M press w/guage really opened my eyes as to how little of a difference neck thickness, carbon in neck (or lack thereof resulting in no lubrication) and annealing vs. non-annealing affects the seating pressure. I think you will find that you will just pick an arbitrary resistance reading on your guage just a little lighter that most of your seatings fall around and use it as the "standard" you are trying to get the non-conforming cases to. I use this primarily as a new brass tool to get my cases to all seat as close to the same as I can. I'll tell you - just because they are the same measurement in thickness (per my ball micrometers and various measuring tools), you will still see variations in seating pressure that can be adjusted for by using some 400 wet/dry paper on the necks till it gets to where you want it. Each time you test it and it is still too much seating pressure, you need to resize and sand again. If I don't get it right in three tries, I anneal the case before proceeding again. Pain in the ass but only go to this extreme for new brass to be used in matches - not practice. Alternative is to shoot every load over the chrono and sort brass by FPS - then work on the necks in same fashion. This method is even more of a pain - but even more accurate when all said and done. Downside is obviously more range time and wear on the barrel, decreased brass life, component usage, etc. I lent the press to my neighbor and he found that by simply not chamferring the inside of his case mouths properly - it was creating big problems for him that he did not previously know existed. You can just look at the readings while seating your bullets as you always do and see right off how uniform your seating really is.

 

[johara1]

There is no magic number, the one that works with the bullet and the set up you use. Mine at present is between 30-32 is what i shoot for, last year the way i was set up was 24-26. So it is not a given, the gun shoots good now and it it did before with a different bullet and different neck tension. You got to learn to dance with it........ jim

 

[jlow]

So searcher, do you know what specifically is changed when you adjust the necks with the 400 wet/dry paper. I know you are trying to get consistent seating pressure but what I am more interested in is what physical difference in the necks you think is affecting seating pressure and how that is changed by the sanding?

 

[jlow]

Wayne, be kind! I was trying to be serious! :

 

[johara1]

WOW........... jim

 

[pmarauder]

I think Tom uses nose grease on his bullets to get his seat force just right...... Just a little goes a long way....

 

[jlow]

Well you are better at pretending than I am,...I am proud of you
Wayne.

LOL!

 

[searcher]

jlow: I sand the exterior neck of a case with wet/dry when I find the case seats with more difficulty than the "standard" measure of force I am looking for. I find that carefully taking off a very little at a time and rechecking along the way - you can get all of your brass to seat very nearly the same. I believe it provides improvement at 600 and 1,000 for sure. I do a simpified version with wider tolerances accepted on my point blank cartridges. Again, I don't think any of this is needed to be competitive. I am always striving for the one hole at 600 - a lifetime journey...

 

[searcher]

jlow: after re-reading your question, I probably should have added that despite the micrometer showing a certain neck thickness, VERY small deviations in neck thickness (too small to try to attempt fixing with your neck turner) cause seating pressure differences that are inproportionate with what one would think it to cause. In my own experience, I have found that neck turned brass - no matter how close you get them to one another in thickness - are not perfectly the same. This technique helps to fix that - if one were so inclined to want to do so. I had read of another top F-class shooter doing this to his brass and it made sense so I tried it. It works for me as well. Sorry if I led anyone to believe this fixed other case ailments.

 

[jlow]

Searcher – thanks for your reply and detailed info.

So you are sanding the exterior neck? A little confused here since that does not touch the bullet. Would you be meaning the exterior surface on the inside of the neck? However, your second answer would seem to imply the exterior since it deals with neck thickness. Right now my neck thickness variation after turning hovers around 0.0002” (ES for 17 pieces of brass last time I measured) and that translates to about 1.4% max variation for a 0.014” thick neck (Lapua 308).

Don’t have the K&M tool (yet…) and so hard to figure out if there are significant variation, don’t feel it at least on seating but feel of course is not quantitative.

 

[searcher]

Yeah - I'm sanding on the EXTERIOR of the neck. When you size the neck, the measurement variance gets, as we know, pushed to the inside where contact with the bullet is made. If we take a little off the outside, then size, the inside will be changed to a smaller diameter. Regardless, I keep tweaking them this way with the sandpaper, resizing, annealing when necessary and re-seat them until they are in the same range of seating pressure that I have defined as my parameter. At this point, I'm no longer relying on the micrometer for neck thickness. I'm relying on true seating pressure instead. Afterall - it isn't the thickness variation that causes the seating variation - it is the resulting pressure variation. On that thought - we can go by pressure alone - which is the whole purpose of the K&M press, right?

 

[searcher]

Jlow: I re-read my post after sitting down and relaxing and realized that I made a good goof on my example. Once you take material off the outside of the neck, size the neck, the inside of the case neck would not be of a smaller dimension - I think you get the drift though. I type faster than my mind works most often now...

 

[pmarauder]

I think you guys may be barking up the wrong tree. there are other things going on with the inside of your case necks that are more important than one micron of brass thickness...

 

[bozo699]

I think you guys may be barking up the wrong tree. there are other things going on with the inside of your case necks that are more important than one micron of brass thickness...

Amen!!!!!
Wayne.

 

[pmarauder]

You do have to admit though Derek ,...after a hard days work it's good to laugh!
Wayne.

Yeah, but you cant fault a guy for trying...... Consistency is a formula of many different things. You have to assess the value added processes against the non-value added ones. Believe me, I have done them all.
The paper at 1000 yards can be brutally honest sometimes!!

 

[jlow]

Searcher – thanks for the additional info. I agree with you that the sanding will changed the neck thickness and may affect neck tension without changing internal dimensions. However, I have to admit that I am skeptical of the effect of removing the small amount of neck on neck tension but I am no expert and am always still open to the idea that I could be wrong. In the end, if it works for you, you got to do it…. One question I have for you is how do you remove material from your neck in a consistent manner across it’s surface?

The reason that I have not gone the route of the K&M “Seating Force Measurement Gauge” is that it requires you to buy not only the gauge but the stand and also the seating die, so that adds up to quite a bit but I may still make the plunge – LOL!

The other reason is I am not 100% sold on the idea that equal seating force = equal neck tension. The reason is currently I am pretty happy with the consistent feel of my seating force but I’ve had to pull more than a few bullets from rounds that I ended up not shooting (pressure signs) and I am always a bit surprised by the inconsistency of how hard it is to pull those bullets. Granted, I did not measure the force for the seating and that could be my failing but that at least is my uneducated opinion.

 

[searcher]

Yeah, this isn't for everyone. We all question the techniques of others at times. If we didn't, we might all be doing it wrong! As for how I sand down the necks, I get a piece of 400 wet/dry (1/2 sheet) and fold it up until it is about 2"X2" which makes for a pretty stiff backing. I chuck the case into my drill press directly (or 1/2" DeWalt drill sometimes) put on low speed and run the paper over the neck in a uniform manner, using constant, equal pressure. I start at the mouth, work to the neck, then back. Trial and error will show how much to sand to get close to your objective. I don't worry about getting right up to the shoulder as I don't seat my bullets that far in. This all sounds far more tedious than it really is. I can prep 100 pieces of brass in about 1 1/2 hours because you are not going to do any work on about 25% of them and only a handful will require more than one or two attempts to get it right. I know some people who test all brass over the chrono to spot ones which could cause them problems. That takes just as much time - plus wear on the barrel. And yes, there is more going on in the neck than thickness, yet I do strongly believe in unform bullet seating = uniform tension. When I get a flier, I now tend ot look at other potential causes