Thursday, September 12, 2019

Vectan A0 and GM-3 smokeless propellants

This data is from my loaders, with the manufacturing "lots" I bought, with my bushings, weighed on my scales. If you want to try Vectan powders you need to follow best reloading practices. If you don't know what they are, don't reload.
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GM-3 upper-left corner. A0 upper-right corner. Unique bottom-center. It is useful that the powders look different.

Executive Summary: I will be running smaller powder bushings in my Lee Loadall-2 with the two Vectan powders than I did with Unique.

GM-3 in the 12 Gauge
I planned to run 22 grains of Unique in the 12 gauge with 1-1/8 ounces of shot. With my lot of Unique and my set of bushings, that was the "171" bushing. I have run as high as 25 grains of Unique and been below book-max.

The the lot of GM-3 powder I purchased also threw exactly 22 grains of powder with my 171 bushing. From the Graf Reloading supplied Vectan Reloading data, the vast majority of hull-wad-primer combinations listed a max of a tiny whisker above 20 grains.

Mindlessly switching powders without verifying data (recipes) and weighing charges would have resulted in a 10% over-charge from my modest Unique loading and a 25% over load if I was using the hotter Unique load.

---The 155 bushing (approx 2.5 cc) threw 20.3 grains of GM-3. That is where it is going to stay.---

AO in the 16 gauge, one oz
The sixteen gauge is set up with the 148 bushing and, for my lot of Unique, throws a charge of 18.5 grains. Again, this is not a max load.

The AO throws a charge that is 10% heavier than my lot of Unique. AO is a slower burning powder and the 20.3 grain charge is slightly below max according to Graf's data but will be noticeably warmer than what I am shooting with the Unique. Since most of these loads are destined for a lightweight, single-shot, I intend to install a smaller bushing to reduce the AO loads.

AO in the 20 gauge, 7/8 oz
The 20 gauge reloader is set up with the 134 bushing and throws 17.5 grains of Unique. Again, that is for the lot of Unique I bought. Yours may differ.

Based on the AO throwing a 10% heavier charge than the Unique, I expect the 134 bushing to throw charges of 19.3 grains.

The Vectan data has several hull-wad-primer combinations that list 17 grains of AO as the max and one H-W-P combination that lists 15.8 grains as the max. Obviously 19.3 grains is much more than 17 grains and I need to use a smaller bushing if I don't want to have to pay much attention to hull-wad-primer combinations.

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