Extreme spread?

I agree with almost everything you said UncleNick.

There are several good articles out there on primer performance, one of the best is This one by Laurie Holland.


http://www.targetshooter.co.uk/?p=1471

Since I read Hollands article I make the final step of a load a primer test like this

https://imgur.com/a/aNCjhDO

The only thing you said I disagree with are the tools sensitive to seat primers correctly. In one of his primer articles Holland expressed his fondness with the old style tray Lee. I have one as a standby but don't care for it.

Some think the magazine fed primer tools can be dangerous. Perhaps they can but with my left hand issues This is what I use most of the time these days

http://rcbs.com/Products/Priming/Tools/Automatic-Priming-Tool.aspx

Last evening priming new Lapua cases for the first time I could feel the primer seat in two stages using that bench primer. The goal now is good enough case prep so I always get that two stage feel. Between primer feel and seating feel you can tell when a case is past it's accuracy peak

One test everyone can do no matter how they prime is just run your finger over the primed case. You want feel the primer slightly indented below the case when you run your finger over the primer. You can use the depth gage part of your caliper to see if they are uniform also if you want
 
If you have a load that you are trying to tune up/improve, the easiest thing can sometimes be changing primer brands and working up again.

If you are tuning a load you will notice a range where the case fill ratio is the happiest.This will net you the lowest ES's with that primer/powder combo (sometimes this correlates with your accuracy node)

It is thought that it is a powder type, primer type & bullet weight vs. case fill ratio that makes up the majority of extreme spread.

Your developed load should be in the middle of a accuracy range of at least .3 tenths. Fretting over 1 tenth variations in powder to get your load shooting is not the best load choice. Choose a different range or a different primer/powder combo.

Getting below 25 fps goes into cartridge type X vs X type case design, as well as perfect bullet release. Perfect bullet release has much to do with bench rest style case prep and chamber dimensions etc.
 
The load that produces the smallest SD and ES gives the smallest groups is the one I'm looking for. Large SD and ES usually produces large groups.
 
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