Some chrony data and questions

[Shrinkmd]

New toy at the range, and it seems to have worked well, so far.

I was shooting my 1911 gov't model, with some factory and handloads.

Wolf 45acp: (40 round sample, was 50 but somehow they didn't get saved)

High: 808
Low: 755.7
E.S.: 52.3
Ave.: 783.6
S.D.: 12.6
95%: 4.1

200 gr LSWC, WCC 98 Match Cases, Federal LP, 4.6 gr Bullseye, 1.242 (100 rounds)

High: 823.7
Low: 773.3
E.S.: 50.4
Ave.: 803.2
S.D.: 8.5
95%: 1.7

then, some very mixed 45 ACP 230 LRN, Wolf LP, 4.5 Bullseye, 1.265 (100 rounds)

High: 810.2
Low: 731.1
E.S.: 79.1
Ave.: 771.4
S.D.: 13.6
95%: 2.7

and finally, same exact load, but all in CBC (magtech) cases (42 rounds)

High: 787.7
Low: 733.3
E.S.: 54.4
Ave.: 760.7
S.D.: 12.1
95%: 3.9

The amateur scientist in me is impressed by the difference in the federal primers/match cases load. Obviously, I would have to test the federal primers against wolf or other brand to see if the standard deviation difference is the same.

And now I forget my other statistics. How do I do a T test to figure out if the difference in standard deviation or extreme spread between different loadings is actually significant?

Other question is, should I be loading those 200 LSWC a little hotter? Is 800 fps the accepted average velocity? It looks like power factor would be 160,000 so they might be a bit short if you wanted to make 165,000 no? It looks like my 230 hardball loads are well over the line.

Once you start chronographing your loads, do you ever shoot without one again? More junk to bring to the range...

 

[Bailey Boat]

A chrono will give you some interesting data, it's how you use the info that counts. You can become obsessed with it and not see the forest for the trees.
I've been using one for years and wouldn't do load development without one but....... I'm mainly after velocity and accuracy, what else REALLY matters??????

 

[Jim Watson]

I am probably further from my statistics classes than you are and can't help with that,

But if you need Major power factor for IPSC or IDPA, you are going to have to bump that 200 gr load up somewhat. Even the high end does not reach f-165. You need at least 170 for a little safety margin, maybe more.

 

[Shrinkmd]

Additional question

I won't start a new thread, but here is an interesting question:

When I set my powder measure, I was advised on a video to weigh ten charges together to get the average for the load. Poor little scale is only accurate to 0.1 grain so they say, but if you weigh out ten charges, in theory you can see what your batch average is. So in theory, even if the individual charge says 4.6, a batch made up with a ten charge weight of 46.1 gr should be different than one which weighs 46.6 gr, even if the scale mostly reads 4.6 for both at the individual level.

Does this make sense? Has anyone experimented with making changes at this level of fineness and seeing it reflected in the average load velocity? Of course, these tiny changes in pistol data probably don't matter, as they all likely shoot better than most people's hold. But I am getting much, much better at pistol (reloading does indeed equal shooting more, and not saving money, so to speak).

 

[Marlin 45 carbine]

good report and questions, I don't compete formally so have nothing to add except I'd be suspect of Wolf primers. I have used MagTech with good results - the cheapest primers I could find besides Wolf. and MT brass is good too.

 

[mongoose33]

Two-sample T-Test for means:

I calculated it out for the first two data sets; very significant at p<.001.

I also calculated it out for the smallest difference (771.4 and 760.7). Also p <.001.

All the rest of the differences are also significant.

Remember, though, that just because something is significantly different doesn't make it a practical difference.

Further, you also have to ask how the rounds performed in terms of accuracy. Sometimes lighter loads are more accurate, depending on what you are looking for.

In this case, you have the highest velocity and the greatest consistency round-to-round with the Match Cases sample.

 

[Shrinkmd]

Thanks for the calcs. I see my old biostatistics book up on the shelf squinting at me.

Next time I load up some rounds, I will prepare two batches of the 200 gr LSWC, identical except for Wolf LP vs Federal LP primers. That will make for some interesting data. I also might make the rounds a little stronger, go for about 830 to 850 fps.

 

[Radaray]

I agree with Bailey Boat. Don't get too engrossed with chrony data. It's great for load development, but don't get too carried away with SD and ES, especially if the rounds are accurate.

As for velocity, load for what you will be using them for. Don't need very much to put holes in paper, but if you are loading to make power factor, load them up some.