Powder measure bushings

[Willbird]

I was making some bushings for my Star loader tonight, it has a 1/2" powder slide, the bushings are thus 1/2" od and .495" tall .

anyway I hit on a bushing size that throws BOTH 7.0 Green dot and 10.7 grains of Blue dot. which are both listed as max loads for 158 grain boolit by alliant.

some of the other sizes I checked and made working up to that were giving me the idea that it was going to be close to working out that way.

and according to the Lee manual .88cc of green dot is 7.0 grains, and .88cc of Blue Dot equals 10.8 grains, so that confirms it.

I used a .390 drill but with the nylon bushing in a 3-jaw chuck the hole came out a triangle. will have to try the 1/2" collet next time.

Bill

[Willbird]

More research reveals that the .88cc is the auto-disk cavity they say to use, the actual volumes would be.

.8834cc for 7.0 of green dot

.9255 for 10.7 of blue dot

I have two lots of green dot to check bushings with and they show about .3 grains difference, one is pretty new and the other is more than 30 years old, the older stuff throws heavier for a given volume.


It is quite interesting seeing what a given powder measure setting or bushing size will throw in differant powders. Mr. Harvey Donaldson was an advocate of a certian powder volume in rifle ctg. causing the accuracy, he would set a powder measure for say 219 donaldson wasp and lock it, then change powders for differant bullet weights to still end up with the same volume.

Bill

[fecmech]

Hi willbird--I have bushings for my old CH Auto Champ that are .485 tall. According to my notes .390 throws 10.0 Blue Dot and .405 throws 11.0. As you probably know page 3 and 4 of the instructions for the lee auto disc measure give you a great chart for figuring what a bushing will throw in a given powder if you know what it throws in another powder. I have about 20 bushings for my Auto Champ and notes on what most of them throw. I'd be happy to share any sizing info you need. Nick

[Willbird]

Hey Nick, I cooked up a spreadsheet for excel to calculate what a bushing will throw if you input the height of the bushing, the vmd of the powder and the cavity dia. PM me and I will send it to you to play with.

Bill

[NVcurmudgeon]

FWIW, When my RCBS Uniflow measure is set for C.E. Harris' widely recommended load of 16.0 gr. Alliant 2400, it also throws 9.0 gr.Green Dot, which is becoming a favorite low velocity load.