Primer Seating

[jepp2]

Interesting short article: https://www.reloadingallday.com/post/does-primer-seating-depth-matter

I read the article. I guess I have a different perspective than the writer. These are my view, and I'm sure others have their own views and some are more accurate than mine, maybe most.

The article infers that 3 shot groups are adequate to decide the load potential of the rifle given the variables. In my load development I only consider 3 shot groups adequate in telling me if a load will not shoot. I want to see repeatable 5 shot group sizes before I consider the accuracy potential.

The article also suggests that 3 shots are adequate in having a sound statistical base for measuring differences. I consider 10 shots the bare minimum before I start to have any confidence on the ES and SD for the load I am shooting.

I have a guy that I shoot with occasionally. In addition to always boasting about his rifles accuracy and always discounting shots he calls flyers, his claim is about the best group his rifle ever shot. Claims like "this rifle will shoot 0.25" groups all day long at 100m. It shot one group one time that actually measured 0.327". Humm. I referred him to this info that Sierra discusses group size and flyers.

http://bulletin.accurateshooter.com/2021/06/how-to-evaluate-flyers-during-load-development/

 

[Steve Blair]

I bought an RCBS bench seater around 1980 and have used it since. I like it because I can lean on the handle and put my weight on it while standing. Works for me.

 

[Joe Maisto]

Ideally, you would touch anvil to pocket bottom and then preload an additional 2-4thou(crush).
With uniformed pockets this should put cups at or below case head. If you don't provide this sensitizing, or if you over-crush to squish priming compound from between anvil/cup, you can hurt reliable & consistent firing.

Your tool is adjustable and sensitive to contact of anvil to pocket bottom. Or so you think.
You could measure a bunch of primers for unseated/loose height and group them.
Then you could take measurements of touch -vs- touch +.002", creeping into tool setting.

The ONLY tool that directly sets primers at desired crush is the indicated K&M.

All of the tools Mr. Ken Merkle created left nothing to be desired.

 

[Straightshooter1]

Would the accuracy one primer depth gage be a more precision tool to get an accurate repeatable reading?

I have this gauge and I find I get accurate repeatable readings. What I like most about it is the speed by which I can take many measurements quickly and dependably. One can even use it to measure the height of a primers before it's seated using the instruments zeroing anvil to place the primer on.

Then then increase or decrease depth in sucession to monitor results?

This tools makes it a breeze to do this, if this is what one wants to do.



For those who are not familiar with this tool, this is what that tool looks like:

 

[mikecr]

In my load development I only consider 3 shot groups adequate in telling me if a load will not shoot.

I agree, but I view 3sht testing as useful in some areas. I use 3shts with adjustments in full bullet seating testing to get my coarse optimum CBTO. Then that's what I go into powder development with.
On occasions where I've done primer swap testing, 3shts was enough between them to see consistency or lack of.

What's really difficult is cold bore ACCURACY development, where result must be considered with each single shot. No averaging or statistics, just raw truth in capability.
You would of course shoot cold for 5 or 10 shots with a couple hours between. You have to find out that it's real. But if any ONE shot leaves your need, you're done with that particular test. It failed.

No matter how good your gun shoots, try this simple test, and you might learn something about it:
Put up a 3/4" dot at 200yds, pull your gun out of it's case, drop it on bags or bipod and shoot one shot into the dot. Then wait & take a single shot on the dot 2hrs later, then 1hr, 30min, and 10min.
Regardless of precision(grouping), did you hit the dot with each of 5shts?

 

[JFrank]

Im still working on the 21st century primer tool.

 

[mikecr]

 

[jepp2]

I agree, but I view 3sht testing as useful in some areas.

I think we are in agreement. Haven't done the cold bore test except with my hunting rifles prior to use.

I sometimes shoot a 1 shot 10 load increments ladder when I'm just trying to get an initial read on how close my QuickLoad calculated velocities are to actual. But I consider them just a rough velocity measurement for pressure determination (along with the other many pressure indicators).

 

[One Eye Pete]

The Accuracy One primer depth gauge truly is a great tool as is their bullet seating depth checking tool. Both tools give accurate repeatable readings.
The one thing the primer depth gauge taught me is that when loading 100 rounds it is damn near impossible for me to get all the primers within .001 no matter what priming tool I use.
I honestly do believe that the bullet seating depth checker has more of an effect on accuracy and I can usually get those within .001

 

[PopCharlie]

I use a Sinclair primer seater and primer pocket uniformer. The uniformer cuts the pocket to .124 depth. I seat them from .002 to .003 depth. The 205m primers seat to .003. 450s seat to .002. Br4s seat to .002 to .0025. The primers measure .120 to .121. I don't measure every case or primer. I did all the measuring when I got the uniformer a few months ago. I do check a few cases in each batch to make sure they are what I expect. I only do this to be consistent. I have noticed better ES. Accuracy is not any better. However, that's because of my less than stellar shooting ability.

PopCharlie