Understanding Primer Seating Depth, How much "crush" is good.

[justinp61]

What is he going to lose by checking, if it will shoot in the 1's and 2's?

My rifle is a varmint gun, bring out to the fields to shoot rats. If someone has a rifle that's only capable or .5 MOA, or their shooting skills are not at a place where it would make a difference, as other variables would have more of an impact, then yes, primer seating depth is not important in that situation.

As Shakespeare said, "The lady protesteth too much!"

I suppose there is nothing to lose and all to learn. My varmint rifles will average .5ish moa with me shooting them and have at times shot bragging groups. I'm confident that if I shot ten bulls, three shots the average would .5ish moa. We don't have pd's here, if we did, I'd probably put more effort in my load development. My longest kill on a groundhog with my 12lb Savage mdl12 FVSS 22-250 is 470 yards. That summer I killed nine from 416 to 470 with it. I built a LH pack around groundhog/coyote 22-250 on a Savage action that I've killed out to 432 yards with. I have confidence at those yardages with both rifles.

For me reloading is a hobby that feeds another hobby, I too like to experiment. If I hunted prairie dogs and needed a .25 moa rifle, I'd probably try different primer seating depths too. In all honesty though I don't think I could shoot the difference. It would be interesting to shoot ten three shoot groups with your current load to establish a solid baseline. Then do the primer seating depth development to find the sweet spot. After that shoot ten more three shot groups and compare the results with the first test.

Test, then post your results.

 

[RegionRat]

Kid, just going to point out a few concepts to keep in mind in the hope that it helps.

I normally send notes like this privately but I'm putting this here since beginners often read these threads and launch into load experiments without your experience. This is more for them than it is for you.

When testing OFAT (One Factor At a Time), it is still important to remember that the noise and randomness of all the other variables are cruel and those do not take the day off and stay out of the way.

Use only the control load you know the best over many outings and weather types. Flags and understanding weather are important factors, so plan to run control tests each session.

Be careful with the humidity variable when you work with open powder. It is easy to blame primers for issues caused by the other components, so make sure you have enough stable material (batches) for the whole test.

When you are testing something like primer seating, the ignition contribution is still only a part of the RSS (Root Sum Squared) in the results.

It takes a gross change in ignition for a small sample to show a difference. A small change in ignition takes a huge sample to detect.

Primers work "good" over a wide window, so do not expect a dramatic effect unless you attempt what is called a Taguchi Test where the levels are doped to extremes to see if there is anything in them at all.

Using your "tightest" system to run these tests is important since you almost have no chance to "see" primers as an independent variable unless they are gross. Distance will show first, then as the level gets gross you will see it at Hot/Cold and closer.

Making sure your bolt and firing pin system is in spec is mandatory. Many ignition problems begin in the gun rather than the ammo. Fix these first or you are wasting your efforts.

Good Luck and in for the range reports.