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Interesting thanks Welshshooter, both for doing it and taking the time to explain everything. Good to see it is possible to get lower spreads with due care and attention. I have worked with box and whisker plots before, but to be honest was being lazy which was why I went with means and SDs. It is interesting that the IQR is increasing with load. Perhaps what I'll do next time is prepare 15 of 42gr as I have done for this test, and then 15 where I weight each load individually. I'd up the numbers a bit from this test as I get the feeling the difference will be quite small.

I have found that the RCBS powder thrower can give varying results with N140. I drop a charge slightly under my desired charge and tip it into my scale pan then trickle the difference in. Try weighing ten charges and see the difference between them.

jmc67 wrote:I'd be interested to know what type of spread people get in their home loads (and what type of routine they have to follow to get the spreads they see)?

My long distance load is 185gn Berger Juggernauts with 46.5gn N550 in a Lapua case. This gives me 2650fps and good consistency at 1,000 yards.

I use a Lyman 1200 DPS powder system (checking against a beam balance) for developing batches for testing but it's too slow for the quantities I use in competitions so I load those with a Redding powder thrower. That gives me a 28fps ES over 10 rounds which I'm happy with.

Forgot to add Welshshooter, you asked about the powder measure I used - it's the Lee perfect powder measure. I set it up and check it with a Lyman beam scale at the beginning of my reloading session, but do not recheck unless it gets close to emptying and I have to refill.

Looks like 30fps isn't horrendous then. Obviously I need more practice so will just have to make more :)