On an earlier thread there was a good discussion on how to tune for accuracy. The question was asked with the stipulation that you started with a predetermined mold and a predetermined powder. What I'm asking is how do you narrow the field down to the two, three or four powders to start working up an accurate load with a given mold.
In the aforementioned thread Bud suggested:
I have prejudices;
- Reloder #7 powder.
- VV N-335 powder.
I asked if I could start a thread following his perspective about using "prejudices" and he agreed. A few other folks suggested looking at match reports.
I don't have enough time in the saddle working on cast accuracy with any rifle so all I had was match results and the last two Lyman cast reloading manuals. Specific to the match results i took a look at the CBA's 2021 Nationals and I thought it might help the conversation.
- I would be hesitant to put the farm down on this information because out of context some of this information may be misleading.
- Approximately 6 out of every 10 shooters were using a .30 bore.
- Of the 23 shooters that shot a .30 bore there were 13 different powders used. If you exclude the 30 BR the remaining 12 shooters shot 9 different powders. Obviously the variety of powders can be explained by case capacity. Amongst the 23 thirty bore shooters the case capacity ranged from 35.6 to 68 grains H20. Powder charge volunteered on the equipment list ranged from 15 to 27 grains.
- The average velocity of those shooting the 30 bore was 1823.
- If you pulled the data from the 30 BR the average velocity was 1685
- If you looked at just the 30 BR the average velocity was 1973.
- The average bullet weight for all .30 bores was 197.
- The most popular powder for those shooting .30 bores less than 1650 was IMR4227 (3 of 7 shooters)
- The most popular powders for the 30BR was Varget and N135 (6 of 11)
- With the .223 Remington there were three different powders use by three shooters with the bullet weight running from 75 to 85 grain.
- Likewise each of the three 6mm shooters (PPC & CBA) shot different powders.
- With the PBB and the 32 Miller there were 4 different powders used by the 6 shooters.
My observation is that if you were running the same mold that the top 1st or second place finisher used there (not a bad place to start) you would have a better chance of using the match data to help guide you. But with the large number of variables found in cast benchrest (cartridge, mold, bullet weight, powder) there's a case that can be made for personal prejudices or as some call it "experience".
Just my two cents. As I've said in the past, every day i finding gold nuggets of knowledge laying all over my reloading bench, at the range and on this forum. I'm pretty sure that cast accuracy is something that will keep me busy the rest of my life.