So I've had to switch powders and need to redevelop a 45acp load. This means a lengthy chrono session. Just wondering how many rounds to chrono for each load.
Just wondering what everyone thinks is a good number.
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So I've had to switch powders and need to redevelop a 45acp load. This means a lengthy chrono session. Just wondering how many rounds to chrono for each load.
Just wondering what everyone thinks is a good number.
Not a whole ton of exp here with that, but i would venture you could see in 20 or so rounds...I know with my handloads when i test new batches its only 20 or so, but like i said im no pro...
Could get away with more or less id imagine, but for me reloading for target plinking i do i dont get caught up in that too much
For me it's 5, maybe 10 at most, *IF* the machine catches the shots. You get a pretty good snapshot of your loads after 5 in my experience.
I wrote *IF*, because of my experience with Shooting Chrony. I had two, one bought in 1995 that got most of the shots, and I liked it pretty well. My second was a total POS after a couple years, was nearly all err's/no reads, read about 6% fast (yes, it was totally unfolded) and had a catch zone above the eyes about the size of a baseball. The company would not honor their warranty, and were snotty... Using a CE Pro Chrono Digital now, and love it. Nearly 100% reads in all lighting conditions, huge shooting area, light and speeds jive with other chronographs, and it's made in the USA to boot.
I do 10 rounds per load. gives me enough data to make a decent estimation of what I need to do
I try to do 10 rounds for each charge weight and I vary charge weights by 0.2 grains to 0.5 grains depending on the range between starting and maximum.
You are asking a statistical question. Obviously the larger the sample size up to a point the more accurate the average and standard calculations will be. You have to ask yourself what you wan the data to tell you. Are you shooting precision rifles at 1000yds , pistol plinking at 15yds or hunting rifle minute of lungs at 100yds
Load development.. 3-5 rounds each until I reach my target speeds.
Once I think I have the load, I will load up 20 rounds. 10-15 will be chronoed. 5-10 will be used to test rapid fire cycling.
If I am doing this for a major match. my Low average will make PF.. For local stuff that don't chrono ammo, My average will make PF.
Depending on the powder being used. I will chrono rounds that are at some of the temp extremes. Putting a mag in the freezer/cooler and warming up another in the sun until it was almost to hot to handle, then chrono to get the best/worst cases.
I've had major PF loads make minor when they got to warm. So when I chrono, I will record the outside temperature as a reference.
If I readjust my press/powder measure, i will chrono it again to make sure it is consistent with my previous data.
I also take samples and weigh a handful of bullets, 10min, but I've gone as high as 85 bullets. And I will factor that into the averages as well. I've seen advertised 180gn bullets weigh as low as 174gn and high as 181gn. I see variances like that mostly with lead rounds. Some of your quality jacketed stuff won't vary that much. Zero bullets have been pretty spot on with their weights.
Rifle, there is no PF for the matches I shoot. So I just use the most accurate load I find. 3-5 round groups at 100yd, then again the 20 rounds, 10-15 through chrono, and rest test rapid firing/cycling.
For handguns I prefer strings of between five and ten shots per load. I go to Teacher's Distribution on Excel if I get concerned about the spread. That's just my bad old habits though.
A lot of Chronographs today will do your Statistical work for you on the spot. I like to go for average loads with the best shot to shot consistency.
The most important thing is to take good notes. Sorry to even mention it but I've seen guys who don't bother to record their data.
I am starting to work with center fire rifle after a long time of not doing it. I'll be working in much more detail on environmental factors that would influence accuracy.
Always good advice. I have a spreadsheet where everything is recorded. Plus I'm using a ProChrono Digital with the USB interface. So I export the results to a file for further evaluation. Especially since the ProChrono only allows for 9 strings of 99. Each load needs it's own string.Quote:
Originally Posted by GeneCC