I know you are supposed to weigh every ten throws or so. I just loaded my first 60 rounds last night for testing next week and weighed every throw for now. I cycled a pound or so through the measure before I started and I kept the measure fairly full all the time, only 60 rounds so I didn't use a lot to start with.

When I get a load that works good and I go into batch reloading, how much can a throw be different and not cause any accuracy issues?

I got the RCBS RC Supreme Master Reloading Kit with the
5-0-5 Powder Scale
Uniflow™ Powder Measure

Stays fairly close but off by + or - .1 every now and then. Is this acceptable? I can't seem to find anything on this in my three reloading manuals.

This all depends on the charge. As you get more powder your error/deviation reduces. A .2gr change on a 10 gr is 2%, the same deviation on a 20 gr is only 1%. etc..... Then when you get to some of the pistol loads which only have 5 grs or less the same deviation jumps to 4%.

Then your scales are only a ±.1 gr. So that is the best you can expect. But there are ways to cut this down by doing multiple dumps weighing each dump then avg.

There are some high accuracy scales that will give a 0.02gr.

Kevin,

You won't notice any difference because there will also be a variance in the weight of the bullets and the cases.
Stick with Ball Powder as it meters more smoothly then extruded powder and will produce more consistant loads.
If you have access to a chronograph you can work up a few batches of rounds weighing the bullets and sorting them bases on weight then do the same for cases and test accuracy and velocity for each group.
A benchrest shooter will notice a difference but you won't see it in a pistol unless it is a competition quality one.

In a single sitting I will get good consistency with either +0.1 or -0.1 in a reloading session, but not + AND - 0.1. For example, say I'm loading 4.6 grains of Bullseye. I am okay with an occassional 4.7 if I'm in the middle of the range (ie, not near max pressure). But I would get a annoyed if I was getting 4.7's AND 4.5's. That's a little more than I would like.

Now as long as your pressure is okay with the upper end of the powder weight (ie +0.1), you can check accuracy by loading up 3 batches of 20 rounds batch and weigh each charge. One right at what you want, one batch -0.1 less and the third batch +0.1 to see if you notice any accuracy differences between them.

To do that the right way, use 4 targets. Put two targets up with one on top of the other. Shoot your first batch. Remove the top target and label it and set it aside, leaving one target up with holes in it. Put a fresh target on top of the existing one. Shoot it with the second batch. Remove the top target, label it, and put up a third fresh target. Shoot.

Now you have three target with one batch per target and a conglomerate target to look at. You can see which weight has the most spread, see if the groups move around, and see if the conglomerate is still acceptable.

Since each powder / cartridge / pistol is a system unto itself, you may find it makes no discernable difference. Or it could make a big difference. If not accepatebl, an option is to try a different powder that meters better in your Uniflow. I don't have a uniflow (that I use), but some others can probably tell you what they find flows well for them. WST and WSF and BE seem to work great for me in my Hornady.

hope that helps... have fun and be safe.
rod

ps, be careful about throwing 10 charges and weighng that to see if the average is what you want. That could mean you are throwing +0.1, -0.4, +0.1, +0.2, +0.5, -0.6... etc and the average is close to or dead on... yet you have wildly different charges.

With a Hornady powder drop, I have found the charge weight accuracy has the most to do with powder type as well as the volume of powder in the cylinder.
For example, with ball or flake powders like AA #7, HS-6, Win 231, (pistol) or AA #2230 I do not have to adjust the micrometer setting, and can remain extremely consistant if I keep the volume within 2" of what I started with. With extruded cylinder type powders like R-22 or Varget, I weigh every charge as I have found variations of 0.1 grain or greater (depending on cartrige).

In handguns @ handguns distances to 25yds, you can have variations as much as 0.5gr & still have great accuracy. Stretch the distances to 50yds & for rifles, 0.1gr variations are still fine. Anyone thinking they can accurately measure to 0.05gr & have it matter are kidding themselves. As PR said, variations in bullet & case volumn can be as much as a combined 3-4gr.

What powder are you using?

I have been using a Dillon 550 since 1984, and the powder measure that comes with it.....

I have noticed SUPER CONSISTENT THROWS w/ HP38/Win231.......appx 5.4 w/200SWC in 45acp

Unique worked pretty well for me in 45Colt

Accurate Arms #7 (9mm), #9 (41mag, 30 carbine), H110 (357 & 45Colt) are ball powders and meter excellent WITH ULTRA CONSISTENCY No problems w/ AA #2 or AA #5 either. (45Colt)

I have loaded many thousands of rounds of 223 that shoot thumbnail sized groups from my AR15.
AA 2015BR was awesome.

BLUE DOT (38+P) was somewhat more erratic; a smidge light for a few throws, and then a heavy throw.