What is an acceptable Extreme Spread?

[johara1]

How much do you full length size a case shoulder and base? How much do you set the shoulder back ? What kind of clearance do you have on the loaded round? how much neck tension do you use? Do you trim and point bullets? do you weigh primers? I tune at 100 yds. for 600 and 1000, to me repeatable low ES and sub .1 groups are what I look for... jim

 

[Billy 30-06]

Your barrel may not like the lot of Varget you're using. I would try using a different powder like IMR 4064. My barrel gets much lower SDs with 175gr SMKs using IMR 4064. My load with the 175gr SMK does quite well @ 1000yds. The same lot of Varget does quite well with a different bullet like the 185gr Juggernaut. For shooting @ 1000yds you may want to try some Juggernauts. They have a noticeable edge over the 175gr SMK.
Billy

 

[JimSC]

change one thing and everything changes.

 

[BenPerfected]

change one thing and everything changes.

I agree, especially the weather.
Ben

 

[lawrence97]

A single 100 yard 5 shot group can be very tight with a high ES and SD and it can also be a very large group. That is why making a choice based on one tight group is wrong. 20 shots with a decent ES/SD is best and several 20 shot strings gives more meaningful data.

Small samples are a poor choice, large samples tell you what things will look like in the long run. I’d rather have a consistent 1/2moa vs a random 1/4 moa.

To answer your question “what is an acceptable extreme spread?”

I’d say find what shoots with consistent/acceptable accuracy out of your rifle and that ES/SD is what is acceptable!

 

[johara1]

Yes....SOOOO many variables in both technique and materials! Examining the end result(s) is usually what tells you what/how to do things---what is working and what isn't......and the end result is GROUP SIZE on the target. This all would be easy---like using a cookie cutter---if every batch (lot number) of brass or power or bullets (Or any components) was always exactly all the same as all the others previously used, but that is pretty much NEVER the case and one has to experiment to find the "happy combination" any time anything is changed. Also, a lot of people expect that what other folks are doing is GOING TO WORK for them in THEIR rifle, but that almost never happens! Yes, a lot of the time what was previously used or what someone's buddy uses can be a very good STARTING POINT, but is not usually the BEST (discoverable) combination or technique. Sometimes one lucks out and just continuing to do the same thing and/or using the same components does happen to be the "happy combination" that gives the best (or, at least, ACCEPTABLE) performance, but often adjustments one way or another are required AFTER a period of some testing and evaluation. It CAN be a tedious (and sometimes expensive in terms of time, barrel life/wear and actual component costs) process, but is usually interesting!!

If you use the same reamer and dies, 20 different barrels shoot the same load. You only have waste one barrel hunting the perfect combination. There is never acceptable combination, never be satisfied that it is good enough....... jim

 

[243Mendoza]

Here is good short lecture on why statistician prefer standard deviation over MAD (read the comment and not the video)
https://www.khanacademy.org/math/cc...statistics/cc-6-mad/v/mean-absolute-deviation

 

[johara1]

A single 100 yard 5 shot group can be very tight with a high ES and SD and it can also be a very large group. That is why making a choice based on one tight group is wrong. 20 shots with a decent ES/SD is best and several 20 shot strings gives more meaningful data.

Small samples are a poor choice, large samples tell you what things will look like in the long run. I’d rather have a consistent 1/2moa vs a random 1/4 moa.

To answer your question “what is an acceptable extreme spread?”

I’d say find what shoots with consistent/acceptable accuracy out of your rifle and that ES/SD is what is acceptable!

I look for at least four 5 shot groups in a row with low ES. The reason for four 5 shot groups is to see if the group is moving around due to barrel heat, plus seeing the shape of the group and I will want .1 groups at 100 yds. from all of them.... jim

 

[Ned Ludd]

ES gives you some idea of how much vertical variance you can expect on a target for a given load at some specified distance. SD gives you some idea of how the shots will group due to variance around the average velocity (i.e. variance from the mean). Neither one is perfect, and both provide only limited information, as neither one tells you anything about the behavior of any individual shot. As we also know, velocity variance is not the sole contributor to group spread. I personally pay more attention to ES, simply because if the ES is somewhere around 10 fps or so, I know the SD will be a single digit number and 10 fps ES is not enough to cause unacceptable vertical on a target at 1000 yd.

 

[M14AMU]

Neck turning gave us the "most bang for the buck" in consistent velocities. Consistent neck tension is crucial!

For some folks....it takes a long time for them to learn this one fact!!

Annealing and 'dwell time' with an arbor of .3075" helps prior to seating and the use of an Inline seating tool!

 

[SGK]

For those in need of a calculator and understanding of the statistics https://www.autotrickler.com/stats-calculator.html