Thanks guys.

I had the same issue w my Dillon, but I find if I tap the powder bar 2x between each load with the back of my hand (lightly), it's more consistent. Silly, but works.

I have read somewhere that Sierra says that a +/- .03 variance in powder charges doesn't matter at all. I used a RCBS Uniflow in the past and my charges would sometimes be off 1 grain, now I use a Harrels and the only time that I check my charges now is when I open a new keg of powder.

I have a couple loads that are pretty specific, and +/- 0.3 grains does make a difference. I can also show you loads that adding an extra 0.3 grains would make it too hot to shoot, too.

Jason, I wouldn't want to go over any listed max load myself, but I'm sure there are plenty out there that do, but it's their head if they want to take it off that's up to them (sadly it's usually someone standing around that catches some flying object), I was standing next to a guy when his blew up, caught some powder burns on the arm, he loaded a 06 case full of what he thought was slow burning rifle powder, surprise it was fast burning pistol powder). About the +/- .03, it's whatever the person putting the loads together wants to do. I have 2 loading manuals Nosler#6 and Speer#14 that list their loads that are ending in a .0 or a .5, realizing that the manuals are put together mostly for hunting loads, even the load data that competitors use has to come from somewhere. Just my .02.

Here are a few things I did that helped the consistency on my Dillon 550. I upgraded to the new linkage. My Dillon is over 30 years old. The new linkage is more positive, less prone to sticking and moves the powder bar consistently.
I fasten a couple of fabric softener sheets to the outside of the powder tube with rubber bands—helps with the static.
I don’t leave powder in the measure for extended periods. Unless I’m using it there is no powder in it. I always throw a few charges when I start up that go back in the measure and the same when I refill the measure. Because I’m not sizing and priming when I’m charging and seating (read comment below) my rhythm is consistent. The feel to the process is smooth and the upset to the powder in the measure caused by cases that resize hard is minimal. In other words, there is no inconsistent bumping and jarring of the press and powder measure that affects the powder column. Mt Medic, I think this relates to the same issue you noticed when you rap on the measure.
Lastly and I think this may be the one improvement that gave me the best results----I polished the inside of the powder drop assembly (from the plate down, including the inside of the cartridge specific tube---I forget the part name) with fine (600 and finer) grit cloth and then finished it with polishing compound. When you examine these parts you will notice casting lines and machining irregularities that “grab” or hold powder. Polishing these out really helps the powder flow easy. This pretty much eliminates any “bridging” or sticking of powder grains or flakes in the assembly.
I use Rel 15 and load quite a lot of 223 on it and find that it is pretty consistent now—generally within one to two tenths on the 223 and Rel 15. It is more consistent with other powders and cartridge cases----it rarely varies much at all in a 44 mag with Blue Dot and I use it full progressive with the 44. But the carbide dies promote a smooth sizing process and I believe this helps. Plus the tube diameter that the powder flows through is larger.
TAC, IMR 8208 and any of the Accurate ball powders meter well and are consistent. I’ve even used it with 4895 with good success.
I have the adapter for it and have a BR-3, but my BR-3 doesn’t do a whole lot better when I tested it, so I don’t bother. If I want charges right on the mark, I use a Chargemaster so every load is weighed.
I’ve shot the loads ran on the Dillon against loads with weighed charges and loaded on a Bonanza (same dies) and out to 600 yards I can’t tell a bit of difference. But to clarify, the Dillon is not used as a pure progressive for my rifle cartridges, I use it in stages, something like this----tumble dirty cases, lube then size and de-prime on the Dillon, tumble to remove lube, trim on Gracey, vld chamfer, prime on Lee hand prime, finish loading on the Dillon.
Yeah, I know, sounds like a process and a half, but I believe in doing it that way, so I do it.

Dillon's answer to my question. I haven't tried it yet.

First, dump the powder, remove the powder bar, and clean off the bar with alcohol, do the same with the inside of the housing. Then re-grease the rails on the connector body collar where the measure slides on it.

Thank you,

Dillon Precision Products, Inc