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Marks on primers from seating

Dolomite

Silver $$ Contributor
I started seating my primers deeper .005 and noticed the seater stem marks on the primers. I’m using an older 21st century hand primer seater.

This doesn’t happen if I seat the primers .002.

My question is am I affecting the primer ignition in anyway? Does this hurt accuracy?

My accuracy is sporadic so I thought I need help from others who have more knowledge.

Cci450 primers. Seating .005 below flush.
 

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When primers are seated to the bottom of the pocket, they can be flush with the case head to .008" below (SAAMI)

Primers are seated by feel, not measurements.

Your primers will fire.

Some reloaders uniform the depth of the pockets with a tool.

The instruction for your seating tool only work with uniformed depth of the primer pockets.

"Adjustments/Setup
Your new priming tool comes fully assembled. All you need to do to begin using it is ensure it is adjusted properly. Primers should always be seated against the
bottom of the primer pocket with care taken not to mash them. To adjust the seating depth, turn the knurled head (Figure 1 – E) clockwise as far as it will go then
back it out 25 clicks. This will put you very close to a proper adjustment. Next, seat a primer and note the depth and feel. If the primer needs to seat deeper, turn the
knurled head clockwise. If the seating feel tells you the primer was fully s±eated before the end of the stroke, turn the knurled head counterclockwise. Each click of the
knurled head will adjust the seating stem .001”.
 
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Dolomite said:
I started seating my primers deeper .005 and noticed the seater stem marks on the primers. I’m using an older 21st century hand primer seater.

This doesn’t happen if I seat the primers .002.

My question is am I affecting the primer ignition in anyway? Does this hurt accuracy?

My accuracy is sporadic so I thought I need help from others who have more knowledge.

Cci450 primers.
Click to expand...
The primer seater that you are using seats primers based on some dimension that you decide that you want them to be below flush with the case head?

Danny
 
I’d back off the amount of stroke on the 21st Century primer tool, {one click is supposed to be .001”} as you obviously are bottoming out the primers and then compressing the center even more as there is no more place for the primer to go.
I would worry that you may have a primer go off if you get enough compression and it is certainly not doing any good to the primer to have that distortion in the face.
You are also putting a lot of expansion pressure on the pocket itself and that may lead to premature failure as well.
I too use Peterson 6BR cases and a 21st Century tool and though I have a primer pocket truing tool I have found that it is unnecessary as the cases are already to specification and no material was being removed.
I just seat the primer {450’s} to the bottom of the pocket and that is still below the face of the case by one or two thousand and means that my head space is not effected by the primer standing proud of the case base.
That consistency alone is going to have more effect on accuracy than getting more primer depth and most likely by distorting your primers you are adversely effecting their ignition and therefore the burning rate of your powder in turn affecting your ES/SD and ultimate accuracy at the target.
 
If pockets are uniformed. It is possible to seat to a very specific crush. Not just below surface. In the OP, case he isn't sure where he is at, but is crushing to the point of primer indentation. Too much. Or You could use K&M primer seater and measure and seat for each specific case. There is an easier way, however much more costly. Primer seating Ignition could be a factor. It pays to be exact imo.
 
I don’t know about the depth measurements but seating Federal 210’s into new Hornady 6.5 Creedmoor brass is the closest thing to giving birth a guy can get. My primers have those marks and Ive never experienced any firing or accuracy issues. It’s just extremely hard to seat them.
 
Dolomite said:
I started seating my primers deeper .005 and noticed the seater stem marks on the primers. I’m using an older 21st century hand primer seater.

This doesn’t happen if I seat the primers .002.

My question is am I affecting the primer ignition in anyway? Does this hurt accuracy?

My accuracy is sporadic so I thought I need help from others who have more knowledge.

Cci450 primers. Seating .005 below flush.
Click to expand...
The seating stem tip must not be smooth. You couldn't get the marks you have with a smooth stem tip.
 
I am betting you have some shaved off brass in your seater stem edge?
Clean the seater stem and back off pressure or
Are you using the proper seater stem? There should be one for lg rifle,lg pistol and one for sm rifle,pistol

Looks like you are using the small and rotating case and pressing @4-5x? With too much pressure
 
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I use the small rifle stem and yes rotating brass and seating again. It appears the stem face is smaller than the actual SRP. There is no brass in the stem shaft area, I double checked. I'm going to adjust the seating depth till the indentations are gone.
 
Dolomite said:
I use the small rifle stem and yes rotating brass and seating again. It appears the stem face is smaller than the actual SRP. There is no brass in the stem shaft area, I double checked. I'm going to adjust the seating depth till the indentations are gone.
Click to expand...
Why don't you just do it the correct way: ditch that depth adjustable tool (which is probably expensive), then seat each primer by feel to the correct depth of each pocket and be done with it. Secondly, get a primer pocket uniformer and use it. That way, all of your pockets will start to get to the proper and same depth as each other.

Danny
 
Houston, I think we have a problem! I used a 21st Century and do not get the marks you have when seating. I've seen that mark when crushing the primer and that is far more than .005 below flush. Do as @Alex Wheeler suggested, seat until you "feel" the primer bottom out then if you must "crush" it just a tad and you can do that with the adjustability of the 21st Century primer tool.
 
I think the first question is why the change to go 0.003" deeper? Then, how deep are the primer pockets, vs. how tall are the primers from bottom of cup to anvil, and bottom of cup to top of cup? As others have said, you're probably way past full crush - your spent primer cups will be curled inward, or crushed if so.
Have you seen a difference in ES/SD with the change in primer depth, change at the target? Better? Worse?
 
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64Rambler said:
I think the first question is why the change to go 0.003" deeper? Then, how deep are the primer pockets, vs. how tall are the primers from bottom of cup to anvil, and bottom of cup to top of cup? As others have said, you're probably way past full crush - your spent primer cups will be curled inward, or crushed if so.
Have you seen a difference in ES/SD with the change in primer depth, change at the target? Better? Worse?
Click to expand...
I was wondering the same about how deep the primer pockets are??? That's one of the first things I look at before seating primers in a new batch of brass. I'd expect his Peterson brass pockets are ~ .120" deep. CCI 450 cups are at .113" tall and my CCI 450's are just over .120" tall overall. Given the cups are .113", there should be plenty of room too seat them .005" below flush. But, given those numbers, .005 below flush is a lot of "crush", though there's still .003" to go to get the cup to the bottom (assuming the bottom of the primer pocket edges are square and not rounded).

I've also got a 21st Century hand primer and I've never had any seated primers look like that. . . even when I've over done it (where I might see the the primer slightly flattened rather than those marks).
 
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