Thread: 223 - unusual results

A few weeks ago I tested a cobbers 223 - a nice wee Sako 75. As I recall it's never been a reliably "good shooter" but perfectly OK for hunting.

I had some Belmont 62gn ammo that wasn't up to much in my 223 so commenced with it.

After 5 shots I happened to look at the chony and holy cow, the ES was really low, so I kept going to 15 rounds. For the 15 the ES was 14.9 and the SD 4.7, As far as my experience goes that about the best ever result I've seen or any 223 ammo including reloads.

The group however, a distictly average at 44mm (at 100M) so - thoughts (apart from poor shooting haha) on how such a low ES translates into that sort of group?

Read up on barrel harmonics

If barrel harmonics are unrepeatable/variable shot to shot then the poi suffers regardless of how exact each velocity is

Haven't you watched the Hornardy #50 podcast. Harmonics are so yesterday.

Greetings,
ES and SD are poor indicators of accuracy especially at short range as you discovered.
GPM.

Originally Posted by Tentman

Haven't you watched the Hornardy #50 podcast. Harmonics are so yesterday.

ES and SD are what you work on after you have tuned the load to the barrel, they are in the info stack at the end that shows you why you have that 4 inch group at 1000 yards

https://dsiac.org/articles/random-er...er-dispersion/

Velocity consistency is only one of many factors. You could have 15 rounds with identical Velocity (hypothetically) and if the bullets are poor quality with COG offset due to inconsistentjacket thickness for example, they will have relatively high dispersion. Or if the bullet experiences principle axis tilt on it's journey down the bore. Or... etc

None of these are "harmonics".

All the theory is nice but really it's most practical to look at results measured with a decent sample and take pragmatic actions. You can speculate about what a theoretical cause for poor precision is but you can't change it, just get different ammo

Originally Posted by gimp

https://dsiac.org/articles/random-er...er-dispersion/

Man that's an interesting article - quite a bit to digest in there, might take an evening or two to fully understand!

Was it 62 gr FMJ ammo? FMJ often shoots poorly compared to HP or SP.

Also, what twist rate is the Sako?

Originally Posted by gimp

Velocity consistency is only one of many factors. You could have 15 rounds with identical Velocity (hypothetically) and if the bullets are poor quality with COG offset, they will have relatively high dispersion. Or if the bullet experiences principle axis tilt on it's journey down the bore. Or... etc

None of these are "harmonics".

All the theory is nice but really it's most practical to look at results measured with a decent sample and take pragmatic actions. You can speculate about what a theoretical cause for poor precision is but you can't change it, just get different ammo

Yeah. I'm gonna pull the 62s and try some Vmax 60s - I'll keep a close eye on the 3harmotics for those who worry about such things!

It was SPBT, probably Hornardy. Twist is 1:8.

What's the user's requirements for performance? What size target do they want to reliably hit, out to what range?

And what's the mean radius you measured with those 15rd?

The barrel could be touching the barrel channel in the stock?

Originally Posted by tikka

The barrel could be touching the barrel channel in the stock?

Checked that, and bedding. All looks OK.

Originally Posted by gimp

What's the user's requirements for performance? What size target do they want to reliably hit, out to what range?

And what's the mean radius you measured with those 15rd?

He's quite happy just going hunting and knocking animals over and will be completely oblivious to the fact that I find this combination "interesting" !