Powder charge weight variation

[ratbuster]

I'm getting ready to load several thousand 17 Hornet, 20 Vartarg and 20 Practical rounds for high volume ground squirrel shooting coming up this spring. All my load development involves carefully measuring powder as accurately as possible. For high volume reloading I would like to avoid the time it takes to measure the powder for each round if feasible. Last night I threw Accurate 2200 from a RCBS Uniflo powder measure 20 times and then measured them with a digital scale capable of a resolution of .02 of a grain. Throwing 13.5 grains the standard deviation was .02 and ES was only .06 of a grain. These varmint cartridges have a small amount of powder, especially the 17 HH. Would one expect appreciable vertical stringing with a Std Dev of only .02 grains? That amounts to less than 2/10ths of one percent (.0017) of the total charge.

I will test this by loading up 20 thrown measures vs. 20 actually measured and comparing results but I am curious what others have found.

I also tried the same test with H4198 stick powder and it was 10 times worse with half the throws than the A2200 ball powder so 4198 will definitely be measured for each case.

 

[joshb]

That's why I love the ball powders for volume reloading. Very slight variation in thrown charges. I usually do 22~ grain loads for 223. Did 500 Friday afternoon. I check weight a lot during the first 100 rounds and fly after that, checking every 50th round. It's usually spot on. Just don't double tap. I think you're fine, but I'm not a "top shooter". I do pretty good, though.

 

[Shaggy357]

There have been many many many studies done on volume vs. weight when throwing powder charges. Powder is just one variable in the equation on accuracy. Bullet weight, case capacity, primer burn rate, primer depth, bullet seating depth, etc also play a role. Why hold any one variable to a standard higher than the whole of the others?

I load for silhouette shooting. For me, a box is 100. I usually sit down and load 2 or more boxes at a time. Stick powder gets weighted and trickled to within .1 grain. With ball powders, I load them on the Dillon 550. I set up the press to load one round. Confirm every die is set and confirm powder drops clean. I may drop 3 or 4 charges to confirm total of all weight. For example, if my charge is 10.0 grains, I will drop say 4 charges. If my scale says 40.0, I am ready to go. If I am off by more than .1, then I reset the charge and try again. Once I have set up and do one complete round perfect, I try 5 in a row. If the charges drop the same, I run with it. There is nothing to change in the set-up unless I do it, so I run until something changes. If I add more powder, I recheck the charge. If I am going to leave the room, I clear the press and start all over when I get back. I have 38s, 357s, 9mms, etc that I have loaded 1000 in one sitting. 8 pound kegs are great for running long runs without having to work up new loads.

I have a Lyman #55 measure that I have used to load high volume on the single stage press. Charge handle always starts in down position. Up, tap-tap, down. Check the load until dropping perfect. Once set, these powder measures work great. I drop a charge for about 30 rounds in a reloading tray, then seat the bullets. You can get really fast with a little practice.

Good luck.

 

[Lapua40X]

IMO what you have will work just fine. In your place I wouldn't over think it. When round counts get into the thousands and you focus on fine tuning only one or two aspects of the reloading process the chances of it making a great deal of difference in MOA isn't worth the effort. If your vertical stringing (or other group factor) varies by a .016 MOA you're error at 300 yards amounts to about .046 MOA and squirrels are rarely stationary targets. I'd suggest you just load 'em up and watch for the little critters to become active. Then just go out and enjoy yourself.

 

[Dusty Stevens]

A chargemaster would be my choice for that particular application

 

[BigBlueandGoldie]

A chargemaster would be my choice for that particular application

I was thinking the same thing. I have a Harrel's powder measure and I get horrible consistency with RL15 and IMR4350. Maybe ball powders would be better, but I also think a chargemaster would be better in this case.