Standard deviation.

[NF1E]

As of late, I have been loading .223 ammunition for precision shooting. Never paid any particular attention to SD. Well, over the last couple of weeks I have been doing a bit of checking on the results of differing variables. Powder is loaded to within .02 gn which is the size of a kernal. Bullets used are Berger 73 gn bt target and have not been sorted by weight. Primers are BR-4s and I have been told that other primers should lower the SD even more. I did not notice any measurable difference in point of impact at 100 yds. Each group tested was 50 rnds, or 1 of my range boxes. Thought some might be interested in those variables.

New Starline .223 50 cases sized and loaded with 23.5 gn of Varget. SD 20+
" " " 50 cases sized, and weight sorted to 1 gn with 23.5 gn Varget. SD 12+
" " " 50 cases sized, weight sorted to 1 gn with flash hole de-burred loaded with 23.5 gn of Varget SD 6.5+


Whatta Hobby!

[pdog06]

The shrinking SD should tell you that you’re headed the correct direction.
If you’re only shooting at 100yds and not seeing a change in POI then I guess it really doesn’t matter. However if you shot those same loads at say 300 or 400 you would likely see the change.

With the 6.5 and 12 SD, we’re you still using new unfired cases or were they 1x and 2x fireformed cases. That alone coulda made a difference

[NF1E]

All were new and only had a carbide tapered mandrel applied to equal the neck tension. Groups with the rifle used were all in the 1/4" range which would be my wobble factor off a rest. Whatta Hoby.

[Fuj']

My dedicated match brass has four firings on it. At that point, the carbon in the neck is built up
pretty good, and is key to me in bullet release. I did tests years ago, and proved to myself, neck
tension and bullet release really helped with the SD's.....Are you annealing and using any type of
inside neck lube ??

[NF1E]

Yes, I anneal with a Giraud machine. After neck sizing with bushing die, I use a tapered carbide dedicated expander to set neck tension. Whatta Hobby!

[charlie b]

Fuj, does the annealing 'mess up' the carbon layer in the necks?

[Fuj']

Fuj, does the annealing 'mess up' the carbon layer in the necks?

It does not. Just does not get hot enough to disturb carbon. I then use a very soft nylon brush to
swipe the inside of the necks after cooling to knock out any powder soot.

[charlie b]

Thanks.