Top three things to reduce ES and SD

craigp40 · #1 09-28-2006, 08:01 AM

What are the top 3 things you guys do when trying to reduce extreme spread and standard deviation? I've got a rifle that is shooting some pretty decent groups, but my ES and SD are quite high. Granted, I don't have the best chronograph, so maybe that's the problem... But for now, let's focus on reloading techniques.

papa45 · #2 09-28-2006, 08:12 AM

Do't mix components.

Don't mix batches.

Weigh every powder charge exactly.

Hired Gun · #3 09-28-2006, 08:35 AM

One shot groups really cuts it down. [img]/ubbthreads/images/graemlins/grin.gif[/img]
Seriously, using a powder that fills the case as full as possible. Even slightly compressed is very good for ES. Even neck tension. I stay well away from the lands to avoid pressure spikes from that and I use magnum primers in everything.

craigp40 · #4 09-28-2006, 11:23 AM

I do almost all of those, except the mag primers. HG, do you really notice a difference (accuracy and chrono results) using mag primers over standard? The cartridge I'm working with is a custom 7-08, but I haven't tried mag primers yet.

Hired Gun · #5 09-28-2006, 01:06 PM

Yes, I find a solid ignition much more consistant than a marginal one. I chronogrph everything. I even use CCI-250's in my 22-250.

goodgrouper · #6 09-28-2006, 05:58 PM

When doing load development, there will most likely be a low end sweet spot and a high end sweet spot in the pressure curve with large extreme spreads and deviations inbetween. Then once you go beyond the high end spot, the SD and ES will begin to get larger again. Almost all powders will exhibit this trait but some will yeild better accuracy than others while running through the testing.

It all boils down to a huge variety of things that determine how the internal ballistics will turn out, but all you will need to do most times is change one or more of the four components if the accuracy associated with the good deviation nodes is unsatisfactory.

6BR4ME2 · #7 09-28-2006, 06:09 PM

It all boils down to you and what the gun will shoot on paper. Too often ES and SD are not what will give your most consistant load ...and this will vary from yardage to yardage also...so it sounds like you allready have a good load now only go up or down 3 tenths of a grain and see if it opens up or gets better. The load your using now is a great place to start then test it. Almost all bullet powder combinations have two accuracy "nodes" usually at the high end of pressure and velocity and the other at a lower node ...so good luck and try it ...