Ok lease help me and make sense of this please

[Utectok]

So here are four shot strings all shot on the same afternoon same rifle same load?? There was some minor temp powder difference during the day about three degrees. The last load was the 22 shot string with a sd of 12.. the gun was shot at a steady pace but lots of breaks and chats so maybe 10-15 shots at a time and never cooked it .. very variable all day till it settled at the end. I’m a bit mystified ?!
I guess I shot maybe 80 rounds in the day? The strings are time stamped
It’s a new load as I dropped a grain to avoid sticky bolt lift but it was testing at around 3120 with an sd of about 12 before I shot these rounds

 

[ColinBr]

May I ask if you have shot this load previously and have the recordings?

I was also out on the same day and noticed and bit of a difference between then and a previous day in regards to speeds.

 

[Utectok]

Here is an old test of the same load

 

[Utectok]

Oh the 1 June testing was new virgin brass so not anything to do with that

 

[ColinBr]

Ok so nothing major in regards to differing speeds on different days.

Could neck tension variation be the issue? IE new brass or a few times fired brass.



I was getting a 75ft/s decrease in speed compared to the previous outing, using the same ammo.
To be fair though yesterday was very muggy in comparison to the previous time shooting.

 

[Utectok]

Ok so nothing major in regards to differing speeds on different days.

Could neck tension variation be the issue? IE new brass or a few times fired brass.



I was getting a 75ft/s decrease in speed compared to the previous outing, using the same ammo.
To be fair though yesterday was very muggy in comparison to the previous time shooting.

Wow that is a lot of difference

 

[ColinBr]

Wow that is a lot of difference

Yes a big difference and yet little difference in accuracy

 

[Utectok]

I mean all those shots were same day is 70 fps lost in one day unusual? Also the sd was all over the place till the last longer string (last of the day)

 

[Utectok]

Yes a big difference and yet little difference in accuracy

When I lost speed I was dropping of the plate by 3 tenths

 

[ColinBr]

The unit also had an update prior to me heading out yesterday so maybe to many factors to start worrying to much

 

[ColinBr]

When I lost speed I was dropping of the plate by 3 tenths

Were all the brass in the same condition, as in amount of time's reloaded or last time annealed?

 

[Utectok]

Were all the brass in the same condition, as in amount of time's reloaded or last time annealed?

All the brass was virgin on the 1st June

 

[enfieldspares]

I've only one question. What was the group size each string? Extreme spreads, highest velocity, lowest velocity are interesting and can tell us something is not as consistent as we thought but the only really important result is what was the group size?

 

[Mungo]

Here is an old test of the same load View attachment 367937

I don’t see anything strange there at all.

I can model it for you if you want. Your underlying variation is just bigger than you think it is.

 

[scotch_egg]

What was the powder out of curiosity?

 

[Ronin]

Also shows that a small sample of anything does not equate to accurate representation of actual charge - larger sample - larger ES - SD

 

[Utectok]

What was the powder out of curiosity?

N555

 

[Ronin]

N555

Temp sensitivity ,,,

 

[Mungo]

I mean all those shots were same day is 70 fps lost in one day unusual? Also the sd was all over the place till the last longer string (last of the day)

SD is quite sensitive to sample size, especially if your sample size is under about 20 and your 'true' SD is quite large. I suspect your true SD is nearer 45, possibly as much as 60.

 

[Utectok]

SD is quite sensitive to sample size, especially if your sample size is under about 20 and your 'true' SD is quite large. I suspect your true SD is nearer 45, possibly as much as 60.

If I add all those shots together do you think I will have something statistically worthwhile? Sd wise? (60 shots)
I mean I’m thinking I’ll probably crack on and shoot some deer as sd matters little in the sub 400m world I mostly live in… but I do like the odd poke at long range steel hence the results. Sometimes I wish I’d never bought a garmin lol