I'm not familiar with the term "charge bar". I just use the metering insert that came with my Hornady Lock N Load powder dispenser. I bought the one pound of red dot last summer when I started reloading. It was all I could find. It's been fine other than the inconsistent drops with red dot. Only other powder I have used is 7625 and it's dead on every time. I've loaded about 1000 rounds with the red dot and once it's all gone I'm gonna try the Hp38 I have. I heard it meters very well.
HP 38/Win 231 is a ball powder or flattened ball powder that does indeed meter very well.
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I have both the regular rifle rotor and the smaller pistol rotor for my Hornady lock and load measure and it's worth the additional money to get both. The smaller pistol drum is more consistent due to it's smaller diameter - there is less area and volume that is swept as it rotates, so there is less powder to get pushed one way or the other.
I also like the vernier inserts as they make it much easier to adjust the measure to a known charge weight when switching between calibers (although theoretically you could get a separate insert for each load and never change the adjustment between powder lots).
The pistol drum is pretty small in diameter, which improves the consistency, but it also limits the capacity and limits the number of rifle cartridges and powders where it may be useful - as well a limiting the utility with some of the larger magnum pistol cartridges when using bulky powders.
For example, I tried it with BL-C(2) for some .223 loads and found it maxed out at around 22 grains - 3 or 4 grains short of what I needed. It is however great for .22 Hornet loads.
Yep. Smaller drum. My reloading experience is pretty new, but the 7625 drops perfectly every time. Red dot is dead on maybe 50% of the time. The other 50 it's off. Maybe 40% off by a grain of two that I fix with the trickler. But 1 out of ten drops is usually way off. I'm talking a grain of more. That would definitely cause a squib, shooting 2.1 grains when the minimum is 3.0.
One thing I noted with the Lock and Load measure is that it needed SERIOUS degreasing.
When I initially bought it, I gave it a normal degreasing and then discovered that the charges were very inconsistent. Breaking it down, I noted a fair amount of powder was still sticking inside the measure. There was some turn over from charge to charge and the amount that stuck each time varied by a few tenths of a grain on average - as did the powder charge it dropped.
Consequently, it got re-degreased with 90% alcohol, acetone and mineral spirits in three separate operations before it finally stopped holding on to powder flakes. Ball powders were a little more consistent before the thorough degreasing, probably because they were more resistant to sticking, or perhaps just produced a more consistent coating once all the surfaces were covered.
Given your report of only 50% accuracy, and some truly huge discrepancies now and then with flake powders, I suspect that you may have a similar issue with the powder sticking in the measure below the rotor.
You might try aggressively degreasing it with a brush and mineral spirits and see if that improves the consistency.
One trick to prevent the shiny bits from rusting is to given them a coat of neutral shoe polish, or car wax. It will go a long way to helping prevent any rust on the surfaces with no risk of getting oil contamination of the parts in contact with the powder. The same thing will work fine with the exterior surfaces of your reloading dies.