OK... load #1 does NOT mean that is the mean velocity of the load. The mean velocity of the load might be 2525, or 2575. Which is it?? We can’t tell with only one round.
If statistics are not in out favor, load #1 could be 2575 and #2 could be 2550, so it appears that load #2 is SLOWER than load #1??
"There is a decrease!!"
Or load #6 could be 2650, and load #7 could be 2725.
"There has been a radical JUMP in velocities, therefore there is a radical jump in pressure, or some other irregularity"??
The point is, you need a larger pool of samples, and 5 rounds is an absolute minimum to get an “idea” of what’s going on, and 10 rounds per load is MINIMUM to get truly accurate velocity, ES, and AV data.
Three shot groups are adequate for getting mean velocities to run ballistic drop programs.
One shot “groups” are not meaningful.
In the data above…
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I tried a ladder test today with new 7 RUM. I was using Retumbo starting load at 88gr working up to 94 gr by .4 at a time.
Do you typically do this test at 300 yrds? Problem was that most the shots went into two groups with very little vertical spread. Here are the results:
I think shot 13 did not register. I was thinking shots 4,5,6 and 12,13,14. What would you suggest?
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Now analyze the data...
#2 and 3 are LOWER than #1??
#4,5,6 are 80 fps Faster than #1,2,3, and are the same velocity - hello??
# 7 and 8 are the same and only 16-ish faster than 3,4,5??
#10 is slower than #9??
#16 is the same as #15?? but both are 50 to 85 fps faster than 11,12,14???
What does this tell you... by the very nature of statistics, absolutely NOTHING! This pool of data has no information other than the gun shoots bullets and they come out the front. You can NOT draw any information from one shot ladders.
The reason is… the ES is much larger than the increments, so they overlap in both directions.
I appreciate you feedback, knowledge of statistics, and scientific background. I see the problem with the string of velocities that I posted. What do you think would cause this spread? Trust me I do not want to get in a ******* match being somewhat new to this site, but in your process of selecting a perfect load you do not account for any human error. Or I am I supposed to think that you would never miss a wind call or pull a shot. You might reject the perfect load based on human or environmental error. How scientific is that?
We each have our ways of loading for a new gun but in the past I have wasted to much powder and bullets trying to develop a load by throwing stuff at a wall and hoping something sticks.
I shot a 16 shot ladder. picked one load and shot .38moa at 300 yards. Without the information form the ladder I would have been wasting my time picking something out of the blue.
Like I said thanks for your response and I will probably load multiple rounds per weight next time to get some averages. It thinks that is reasonable advice.
If you are not using uniform brass, you will get velocities to go up and down on a ladder. You essentially have 2 variables in your test 1) amount of powder 2) interior size of the case.
To eliminate the case issue, I always try to run ladders with once fired brass that has been prepped (uniformed, primer pockets, flash holes deburred etc.) and then sorted by interior capacity (brass weight).
By using brass that is very uniform, you are eliminating one of the variables. Your velocity spread should be smaller and the nodes easier to see.
If some is good and more is better, then too much is just right.
My mind is a raging torrent, flooded with rivulets of thought, cascading into a waterfall of creative alternatives
Need your help guys...
I want to sort my cases by weight, and I have a strange situation.
270.5gr - 3pcs
270.8 - 10pcs
272.0 - 8pcs
273.2 - 9pcs
273.0 - 3pcs
274.5 - 4pcs
276.0 - 3pcs
Do you thing is a god ideea to group togheter the cases with the same grains (270.5 with 270.8), and 273.2 with 273.9
so on ... In another words not exceding more then 0.9gr.
I know the best groupyou can get with cases on the same weight, but I have to manny on this way.