Primer seating depth and accuracy

[mrobles3808]

Let me have it! Does a relatively expensive primer seating tool such as K&M Precisions with indicator produce better ammo? I have had succes with rcbs and Hornady hand primers, just going off of feel. Can measuring primer seating depth shrink your groups or is this splitting hairs?

 

[BurnOut]

I'm going to caveat this my saying that I /think/ that precise primer seating is done in an effort to ensure uniformity. I would think that in all but the most extreme circumstances, the difference that would be seen on target is within the margin of error for most shooters; that is to say that, for example, on a good day, I can put up fairly consistent half MOA groups, so anything that would fall within that range isn't going to be noticeable to me.

That said, I recently purchased the 21st Century primer seater, and have decided that the rear of the primer should be as close to the rear of the case as possible (without being proud of it; so flush, or just baaaaarely recessed).

As always, I reserve the right to be wrong...

 

[bruddah]

My opinion:
As long as the primer is seated deep enough and fully seated to the bottom of the pocket, you're done. If you feel a fancy priming tool will make that happen for you, then go for it.

I use the RCBS hand priming tool myself, and don't really see how a different product would do any more and better.

 

[MtnCreek]

I uniform pockets and seat till it bottoms out and then apply a little more pressure to seat the anvil against the cup. The reason for most failures to fire for handloads is not seating the primer fully.

 

[Marksman10x]

I used the Sinclair tool for years. It is pretty good, but so is my Dillon 550 that has been modified to properly seat primers. The ammo, including the seated primer, is just as good as when using the Sinclair priming tool and size/seating on a single stage. So to answer your question, I think as long as the tool you are using gives consistent, repeatable, quality results, then you likely will see no improvements down range by switching to a more expensive tool.

 

[Marksman10x]

Here is a link to a terrific article that discusses how to modify the Dillon 550's primer seating depth (and a lot of other good stuff as well) for those that might be interested

 

[Milo 2.5]

I'm going to caveat this my saying that I /think/ that precise primer seating is done in an effort to ensure uniformity. I would think that in all but the most extreme circumstances, the difference that would be seen on target is within the margin of error for most shooters; that is to say that, for example, on a good day, I can put up fairly consistent half MOA groups, so anything that would fall within that range isn't going to be noticeable to me.

That said, I recently purchased the 21st Century primer seater, and have decided that the rear of the primer should be as close to the rear of the case as possible (without being proud of it; so flush, or just baaaaarely recessed).

As always, I reserve the right to be wrong...

This is an interesting topic. One thing you said sticks out, "flush with case head". Is it just me or does newer brass have deeper pocket cavities? Norma, Lapua, etc.., I'm finding a uniforming tool wont even touch till 2+ firings.

 

[bruddah]

This is an interesting topic. One thing you said sticks out, "flush with case head". Is it just me or does newer brass have deeper pocket cavities? Norma, Lapua, etc.., I'm finding a uniforming tool wont even touch till 2+ firings.

The primers should be flush, or BELOW the surface of the case head. Usually they are a few thousandths below.

 

[orkan]

The primer should be below flush, with full contact on all prongs of the anvil. I prefer .002 to .004 of crush. My tool of choice is the CPS, obviously.

Primer seating uniformity most certainly has an effect on velocity spreads.

 

[arm017]

The primer should be below flush, with full contact on all prongs of the anvil. I prefer .002 to .004 of crush. My tool of choice is the CPS, obviously.

Primer seating uniformity most certainly has an effect on velocity spreads.

Could you quantify the variability you would expect on primer seating variability. Say flush vs. .004 deep?

 

[orkan]

With a hand primer, you can end up +/- .003 very easily. The depth ES is more severe the tighter the primer pocket is. With quality tools that have adjustable depths, the variance is much less.

With the CPS we have measured within .0005 average. This is due to the mechanical hard stop in the tool which makes it impossible to exert more force than necessary.