What is an acceptable standard deviation for rifle hand loads vs factory rifle loads ?

[Remtac]

Went out testing two new loads today with the new G2 chronograph.

First was cal .243 with H-4350(42g powder) 95g Berger VLD target
Standard deviation was 10.8 feet per second .




Second was cal .243 with reloader15 (38g powder) 95g Berger VLD target
With a standard deviation of 7.9 feet per second .

 

[benchracer]

Generally, the goal is 10 fps or under. I have found it very rare for factory ammo to test under 20 fps. Most factory ammo has MUCH higher SD's. Either of the loads you list should work, provided they shoot well.

 

[Greyfox]

Acceptability depends on the size of your target and maximum range you intend to shoot. For my medium sized game hunting with a 6.5x284 at 2975FPS, a SD of 6.5(ES of 20 FPS)is more then sufficient to make a vital area hit at 1000 yards. That amounts to about a 5" window. I strive to get my handloads to half of that to give me a better margin of error, or the occasional 1200+ yard shot at a coyote.

 

[Remtac]

Generally, the goal is 10 fps or under. I have found it very rare for factory ammo to test under 20 fps. Most factory ammo has MUCH higher SD's. Either of the loads you list should work, provided they shoot well.

yeah they both grouped ok one was .413" the other was about .5" both at 100 yards

 

[Kansaswoodguy]

I like to get my SD's in the single digits with most bolt guns that's usually not a issue, it's tougher to pull off with gas guns but can be done.

 

[toddc]

SD is a meaningless number for me. ES is not. ES needs to be in single digits hopefully. SD takes too much math anyway.

 

[Mike 338]

Could someone explain Standard Deviation to me in laymens terms?

 

[MudRunner2005]

Is that an app for your iPhone that bluetooths to your chrono?

 

[Remtac]

Is that an app for your iPhone that bluetooths to your chrono?

yes it is

 

[Remtac]

SD is a meaningless number for me. ES is not. ES needs to be in single digits hopefully. SD takes too much math anyway.

To much math ? The app for my chronograph calculates it for me , here is a standard deviation calculator so you don't need to do the math .

Standard Deviation Calculator

 

[Remtac]

Wow from a 10 feet per second standard deviation to 5 fps standard deviation is only a 1.2% difference in probability of hit on a 20" target at 1000 yards vs the 20fps standard deviation to 10 fps standard deviation