I started this thinking I could improve accuracy with better dies, but now I think that maybe I need to work on consistent powder drop, COA and bullet tension.
I believe you are correct and have some ideas in this department.
Most all of this is based on my experience as a mechanical design engineer, my knowledge of reloading, and understanding of physics. Obviously, to get to the nitty-gritty you'd need an apothecary scale capable of 0.01gr accuracy (or better), which I do not own. This because the industry standard is to test and measure to 10 times greater accuracy than you actually need. We desire accuracy to 0.1gr, thus we'd need to test and measure to 0.01gr accuracy. (Maybe one day !)
The basis for all my understand is this... Due to the need for speed in handgun reloading, we are using
volumetric powder measures, but
what we really desire is precise powder
weights. The link between
Volume and
Weight is
Density. So if you want consistent Volumes to deliver consistent Weights, then the place to start is with
consistent Density. This is intuitively obvious, even to a casual observer, and needs no mathematical proof.
• There are a lot of tweaks you can do to any powder measure,
but the ones with the greatest impact are therefore going to be the ones that work toward gaining consistent density. In this one respect Mike Dillon might be a reloading genius, because the latest model Dillon powder measures have the cam actuated powder bar return. The end result of this design is that the powder bar provides the exact same vibration no matter how slow or fast you operate the press.
One source of consistent Density is gained by consistent vibration. Now there are better volumetric powder measures on the market, but you need to operate those presses at a consistent rate, to obtain consistent vibrations, so that the PM delivers consistent weights. But for me, who likes to stop every once in awhile and check things out, this design is simply the ultimate.
Now this snap-back action can be sticky on new Dillon powder measures, so adding powder bar return assistance always helps. To this end you can use rubber bands or the old-style Dillon spring. You're not trying to hammer the PM to death, just add assistance. I add a 5/8" length of wire to the old-style Dillon return spring to get good results.
• The second thing that delivers consistent density is the Powder Baffle. This works by
not allowing the height of powder inside the hopper to pressurize powder entering the measurement cavity.
Consistent fill pressure delivers a more consistent Density. A baffle is so simple and cheap, I can't believe every PM on the planet isn't fitted with one. (Instructions to build your own are
HERE.)
AdditionalAfter you get the vibration and pressure corrected, there are other smaller steps you can take to add finesse and accuracy in adjustment.
• One of the large killers of accurate powder measurement is static cling. If there is a lot of static present, the powder may simply not want to fully release and drop...
especially on all-plastic powder measures. This is generally reduced by wiping the hopper and other internal PM parts with anti-static clothes dryer sheets. Static is typically brought on during very cold, low humidity weather. So the levels present in Vermont are not going to be same as those in Louisiana.
• Adding a squirt of powdered graphite into the hopper helps lubricate the internals. If your powder is black, then it is likely already covered in graphite to do this same lubrication. But a squirt of graphite once a month never hurts.
• Adding a large knob onto the Dillon PM helps by making adjustments easier and small tweaks more precise.
• Using modern powders with known good flow characteristics.
Sport Pistol is greatly preferred over
700X.
BE-86 is greatly preferred over
Unique.
• Starting with the powder hopper at least 1/2 full also seems to help. This also means you need to get get a funnel and work out a process to empty the hopper after loading.
And other things.
