Normal Velocity Deviation?

[Roosterstraw]

What is a normal velocity deviation in factory ammo? Out of 8 shots with Hornady ELD-X there was a deviation of 31fps out of the same box and averaging 2978fps measure with a garmin.

In a different box (same lot #) it was was averaging in the 2950’s which is about 25fps difference.

 

[JF_Idaho]

I think in same lots 40-50fps ES seems pretty normal.

I posted recently about 2 different lots of 6.5cm Precision Hunter having a 140fps spread between them. 2560/2700

 

[Roosterstraw]

140fps seems pretty high.

 

[LAhunter4962]

The ELDx bullets are claimed to be for long range precision hunting but every independent test I’ve read on them shows SD numbers in the teens. Which would be okay out to maybe 400-500 yds but there’s a lot of good factory loads that have those same specs, Barnes Vortex Ammo is one I know of with SD’s in that range as well. The only “factory” ammo I’ve ever seems get better then that is actually Sako’s new line of ammo. I got a chance to shoot some at an event sponsored by Sako just before they released the ammo to the public and if memory serves they were getting SD figures of 8-10. If you want ammo to consistently get 10sd or lower you’re gonna have to look into reloading

 

[Roosterstraw]

The ELDx bullets are claimed to be for long range precision hunting but every independent test I’ve read on them shows SD numbers in the teens. Which would be okay out to maybe 400-500 yds but there’s a lot of good factory loads that have those same specs, Barnes Vortex Ammo is one I know of with SD’s in that range as well. The only “factory” ammo I’ve ever seems get better then that is actually Sako’s new line of ammo. I got a chance to shoot some at an event sponsored by Sako just before they released the ammo to the public and if memory serves they were getting SD figures of 8-10. If you want ammo to consistently get 10sd or lower you’re gonna have to look into reloading

I would be happy with the ELD-X SD in the teens. I’m getting much greater than that though. 31 SD seems excessive. That’s just out of one box. Throw the other box in there and it’s up to 50+.

 

[JF_Idaho]

140fps seems pretty high.

Went back to the data I have written

ES 149 FPS

Average Per Box
2576

2688

Lot #s
3240075
3230674
(Did not have the data which was which)

 

[ColeyG]

Here are the MVs I got using the factory PH ammo when I was setting up to start reloading .300wm and 6.5cm eld-x trying to match the factory MV.

.300wm 200gr factory precision hunter, eld-x
-2866
-2841
-2869
-2865
-2829
-2836
-2833

Avg2848
Tikka T3x with 24” barrel



143gr eldx factory precision hunter, 6.5cm
2646
2637
2617
2612
2620
2642
2587
2628

Avg 2629
Out of a kimber mtn ascent with 22” barrel.

 

[SDHNTR]

All depends on the barrel. Could be 40-50 out of one barrel, then try the same ammo in another and it could be twice that. If you care about SD and ES better take up handloading.

 

[LAhunter4962]

I’ve yet to see any factory ammo that will consistently have SD figures even around 11-12 much less 10 or less. Most “high quality” factory ammo (hornady, Barnes, etc…) will be around 15 fps or so on SD

 

[The Guide]

I would be happy with the ELD-X SD in the teens. I’m getting much greater than that though. 31 SD seems excessive. That’s just out of one box. Throw the other box in there and it’s up to 50+.

Are you talking about ES or SD? Because an SD of 31 would have an ES of over 100 FPS.

Standard Deviation is a calculation of the bell curve of the shot string and a statical estimate of where any given shots velocity will be above or below the median of the shot string velocity average.

ES is the highest speed minus the lowest speed.

Jay

 

[Roosterstraw]

Are you talking about ES or SD? Because an SD of 31 would have an ES of over 100 FPS.

Standard Deviation is a calculation of the bell curve of the shot string and a statical estimate of where any given shots velocity will be above or below the median of the shot string velocity average.

ES is the highest speed minus the lowest speed.

JayView attachment 767690

My bad, referring to ES

 

[Rotnguns]

Are you talking about ES or SD? Because an SD of 31 would have an ES of over 100 FPS.

Standard Deviation is a calculation of the bell curve of the shot string and a statical estimate of where any given shots velocity will be above or below the median of the shot string velocity average.

ES is the highest speed minus the lowest speed.

JayView attachment 767690

Has it been established that the velocity for the shots in a string is normally distributed? I've seen lots of posts about this on other forums, but the sample size of only a few shots seems very small to me. Wonder if anyone's done a probability density study using more than thirty shots? I found a very interesting article from Lake City regarding variation of velocity from different barrels over time; they also included a histogram of charge weight variation of some of their ammo (they tried to fit a normal curve to it, but for at least two of the cases, it's very questionable).

https://ndia.dtic.mil/wp-content/uploads/2018/armament/LustoStubler.pdf

 

[Pharmseller]

When working up a load my goal is ES less than 25 fps.

If you plot the trajectory using various velocities you don’t see much of an impact shift until you get farther than I will shoot.





P

 

[SDHNTR]

I don’t sweat an ES under 50 ish at all. Plenty of studies have been done. That’s not what will make you miss.

 

[mlevimadden]

How many shots are you guys taking for your ES? I feel like there is a big difference between a 3-shot strand with an ES of 40 and a 20-shot strand with an ES of 40.