After a bunch of testing I figured out my old beam scale is basically garbage.   It an old Lyman D700. plastic beam etc, pivots not really square to the beam, etc.  I finally figured out it was just off.  I have loaded with it for years, but mostly large rifle running ladder tests etc to dial in a load.  It didn't really matter much until I started trying to load pistol.

I probably overcompensated and I ordered a tuned scale from Scott Parker a while back and finally got it late last week.   I am amazed at how much better this scale is than my old POS.   Scott sent me a tuned Lyman D5 scale (which is an Ohaus 505).  The parallax is much better.  The scale damps out much better, I can see the arm move with the slightest addition from the trickler.  I ran all my check weights over it and it agreed with all of them, and agreed with the electronic scale.  

I checked weights that were on 5 grain increments using the large poise alone, and then with the large poise with the small poise set on 5. I noted no detectable difference at all.  My old D700 would not do that - I believe the small poise was off by .2 or .3 pretty consistently.

I use a Dillon "Eliminator" beam scale. Can't be any happier with it.

Scott does great work, have "tuned" 10-10 scales from him...and no complaints here...

How much does it cost?  I tried googling but I must be doing something wrong.  I can't find much about his services.

I didn't think he was still tuning scales. His facebook page hasn't been updated in a couple of years.

I noticed that as well.  I sent him an email though and he does still do it.

found this,  interesting read and may help

http://bulletin.accurateshooter.com/2016/02/more-beam-scale-tips-from-scott-parker/

very interesting, I never knew that you could tune a balance beam scale.  Is there anything that a DIYer can do themselves to the scales?

I am interested in this subject, too. From my minimal research, the DIYer can make sure the knives are sharp with no nicks or irregularities and make sure the agates are clean and oil-free. You can also adjust the yoke and hanger so that it hangs "true" and in a fashion that the pan stays level at all positions.

I am positive that Scott has a few more tuning tricks he uses but if you are going to have you scale professionally tuned those are some things you can do yourself.

Scott's work is phenomenal. I had him tune an old Redding scale a while back and the thing is brilliant. It took him a few weeks, but it was worth the wait!

If I recall, this is a side business for him and he's something along the lines of an aerospace engineer.

Scott made an excellent point, if you are looking for precision, you need to eliminate variables and electronic scales have lots of variables, voltage, certain types of overhead lights, cell phone frequencies etc.

In his words "Everyone has access to laboratory grade gravity".

I highly endorse Scott and his work.

I'm a great believer in beam scales: Here's a Redding No 2 I've just rebuilt:

https://www.youtube.com/watch?v=np2XyJlN3Js

and here's my 502 in action:

https://www.youtube.com/watch?v=dnVOoGd1bDU

Nice Work