The smallest sd and es I’ve chrono’d

[V00D00]

And it didn’t group.

 

[43.6N]

Wow.

How many shots? And what cartridge/bullet/powder?

 

[V00D00]

Wow.

How many shots? And what cartridge/bullet/powder?

3

 

[Andouille]

I've chrono'ed some seemingly impossible SD and ED numbers (very low, very high) and odd velocities (ascending, descending, etc), and while it's tough to wrap my head around how they happened, the answer is usually that there were " too few shots" to show a statistically valid distribution.

Three shots wont tell you much other than you have high ES, or potential for low SD. But if the group is poor, then there's no point in shooting more to prove an SD. I have a rifle that has a load SDs in the teens over 50+ shots but just wont group under 2". Probably time to switch bullets...

 

[Castle Rock]

This one did well on target too
6.5 cm, 140 Bergers H4350

 

[TradLife406]

Of course your sd/es will be low with only three shots.

It is funny back when I had the gram I'd post my 10-20 shot sd's in the teens. Guys would be like dang man that's horrible. Well not really since I was actually using a more valid sample size.

 

[wapitibob]

Lost me at chrono.

 

[RME]

I'd post my 10-20 shot sd's in the teens. Guys would be like dang man that's horrible. Well not really since I was actually using a more valid sample size.

I see that type of thing happening more and more as larger samples are becoming more common. It will take a while for all this to work itself out.

 

[hoooogan]

This was by far my best recording. Same charge but different jumps. Forgot to turn it on both times, so I missed 3 shots out of the 20. But combined 11.2 spread with high 3 SD over 17 shots.

 

[Mtslackcountry]

I have a rifle that shoots 1/4 minute 1 shot groups

 

[V00D00]

If I’m 3 shots in and the group is already +.75” I don’t keep shooting. I’ll move on the the next. I’m not trying to waste time or componets. But even three shots that sd and es is respectable.

 

[Harvey_NW]

3 shot group. Looked like a node when I shot a ladder.

Username checks out.

 

[solarshooter]

3 shot group

There's your problem.

Looked like a node when I shot a ladder

No wait, THERE'S your problem.

If I’m 3 shots in and the group is already +.75” I don’t keep shooting. I’ll move on the the next. I’m not trying to waste time or componets. But even three shots that sd and es is respectable.

What if the next 7 fall inside those first 3?

What if the first 3 are in 0.5" and the next 7 go to 1.5"?

How will you know what the true group size is in either situation?

 

[V00D00]

There's your problem.


No wait, THERE'S your problem.


What if the next 7 fall inside those first 3?

What if the first 3 are in 0.5" and the next 7 go to 1.5"?

How will you know what the true group size is in either situation?

I see your point for sure, but it’s the second time I shot it. The first time it was over an inch thought I may have pulled something so I reshot it. Over an inch again. Doesn’t matter if the next 100 go in the same hole at that point

 

[mt100gr.]

I have a rifle that shoots 1/4 minute 1 shot groups

.257 cal?

 

[solarshooter]

I see your point for sure, but it’s the second time I shot it. The first time it was over an inch thought I may have pulled something so I reshot it. Over an inch again. Doesn’t matter if the next 100 go in the same hole at that point

What is your expectation for accuracy? I like to state it in terms of X group size for Y number of shots. For instance, a 1.5" 10 shot group would be my minimum acceptable threshold and my expectation for a medium recoiling cartridge through a factory barrel on a properly set up gun with a decent optic. For a higher quality custom barrel or lighter recoiling cartridge I would expect more like a 1" 10 shot group.

If you really want to cut through the noise, start working with mean and sd shot radius on a 10 shot group.

Until you start using these more concrete metrics, you won't have any real baseline or expectation to compare against. Just a chain of small groups followed inexplicably by larger groups, constant questioning and tweaking of the load, coming up with new theories, tests, and random variables to blame for the perceived inconsistency.

When you start testing with larger samples, all the noise goes away, the guns always do the same thing, and you can see simple differences between low and high quality guns, low and high recoiling cartridges. No voodoo or black magic. No neck tension or action torque or barrel temp or bullet length sorting. It actually sucks as a reloader, because you stop tinkering with stuff and doing experiments and just turn into an ammo mass production facility!