Primer seating depths

[scott/r]

I've just watched the utube video with Eric Cortina and the guy from primalrights regarding primer seating depths. They both agreed that uniforming pockets are a waste of time as the measurement you should be taking is from the extractor rim on the base of your case to bottom of the pocket, not from the actual base of the case. Reasons being that when you seat the primer (no mater which tool you use) the extractor rim is the part of the case that has the contact with the case holder. Makes sense, sort of.
The reason I'm thinking "sort of", is I was always under the impression that it was the firing pin strike that needed to be the consistent part of this equation. Which to me means that the measurement should be taken from the base of the case. Granted that the primers need to be seated fully against the bottom of the pockets, but a thou or 2 (considering most primers have a cup variance of 2 or 3 thou) of crush will take care of that problem.
So, what's everyone's opinion of what is the better option, a consistent firing pin strike or a consistent distance from the flash hole.
Or am I just showing my loading bench ocd again and neither mean much at all?
Scott.

[cheech]

Most important to seat the primer home nicely so it bottoms out , I don’t care on measurements etc blah blah , You want reliable ignition regardless of anything else . I experienced this with brand new Palma cases , I didn’t fully seat them down and had terrible ignition some not going off . I forgot to adjust my Sinclair seater a couple clicks , I reset the the primers and straight away I had not one trouble and my ES-SD were improved noticeably . If your firing pin assembly is all good in protrusion specs you won’t have any problems , just seat them down properly

[John Weigel]

I experimented widely and deeply on this question a couple of years back. See this earlier discussion viewtopic.php?f=5&t=15035#p109438. I think I showed pretty clearly that so far as load development and consistency is concerned the traditional way of measuring seating depth off rim works for consistency in relation to proximity to end of travel of primer in primer pocket. I also found that groups on paper certainly reflected measured variation of primer seating depth. Nothing earthshaking here- just satisfying that popular understanding is correct. Also true appears to be the generalization that one or two thous of crush is ideal. In most of the barrels I experimented with the two thou crush proved best. Surprisingly another accuracy node sometimes occurs at about the limit of possible crush - approx 10 thous of crush.

[scott/r]

Thanks John. A great read. Answers are an awesome tool when you see that someone has gone to all the time and expense to find them correctly.

[PeteFox]

They both agreed that uniforming pockets are a waste of time as the measurement you should be taking is from the extractor rim on the base of your case to bottom of the pocket, not from the actual base of the case.

That's confusing bullshit, because a tool that does that doesn't exist afaik.
Uniforming pockets may be a waste of time period, but if you're into that sort of thing then it is only useless if your primer seater indexes off the rim, which makes the Primal rights tool not so useful.
So you need your pocket uniformer and seater to index from the one place - the base.

I have one of the Primal Rights tools, a nice bit of gear to use but it indexes off the case rim and is way over the top expensive, and no it won't maintain exact primer seating depth.
There is a Lee tool which is a cheap piece of junk called APP or something like that which indexes off the case base by pushing down from the interior of the case onto the base. The case is pressed onto a boss that has a protruding primer sized pin, preset at your desired seating depth.
It is exactly repeatable 100% of the time. It has a crappy primer feeding mechanism that works till it doesn't, which is most of the time, the feeder is in the bin as most of my time was spent clearing blockages. That means that you have to put each individual primer in place .
I use it for a shoot like a Kings. It's a PITA, so I use the Primal rights one most of the time.

(considering most primers have a cup variance of 2 or 3 thou)

My experience is that primer cups are precisely made, the anvils might sit at different heights, but you are not trying to crush the cup imo, you are trying to seat the anvil into the cup and seat the primer rim against the bottom go the primer pocket. Given that there is almost no variance in weight of fired primers, then 2~3 thou variance you quote would have to be accounted for in primer shape. I haven't checked that measurement because there is an anvil in the way and I'm not ripping them out to check as they are made of unobtainium. Using fired primers for this measurement is not valid because the shape has changed.

The thing about primers that is not at all precise is the amount of priming compound.
I've weighed a lot of cleaned up fired primers and found basically no variance in weight
I've weighed even more unfired primers and the weight is all over the place, the results of a small sample (200) are below, all of the difference in weight is priming compound. I have weighed batches of 1000 and the story is the same, a bell curve with lots of outliers.

GM210 weights.jpg

There are enough extremes in weight to in my mind, explain the unexplainable bad shot. Below is the lightest (left) and heaviest primer in batch of 1000 GM210's. Can't remember the weights now but the left side is basically empty and the right side is full.

Primer extreme.jpg

Pete

[PeteFox]

I have also measured primer height including anvil using the setup below

measuring.jpg

The image below shows that primers are not always in spec. I measured this batch of primers twice because I didn't believe it the first time, but the numbers don't lie. Two distinct overall heights in the one batch of GM 210's. The shorter ones are below minimum SAAMI spec, anvils seated well into the cup.

EDIT: Does it matter? probably not because once seated they will all be below spec, and all the same height

heights.jpg

It shows that you have to check everything.
Pete

[Rich4]

You can’t be serious that those two primers came from a single pack of 1000?
If I didn’t know better I’d say they are different brands, even the anvils appear slightly different?

[PeteFox]

You can’t be serious that those two primers came from a single pack of 1000?
If I didn’t know better I’d say they are different brands, even the anvils appear slightly different?

I'm serious, exactly as said and you're paying extra for comp grade primers.
I'm almost out of GM210 and I am now using standard 210's and these is no difference as far as I can tell

In the photo the different colour between the two is the absence of the red wax they use. i've seen video of these being made and the amount of primer compound is pot luck

[Rich4]

Wow!!! And they were always my favourite when I could get them, did you notice if the odd ones were always visually different?

[PeteFox]

No I didn't but it's a kaleidoscope of colours when you look at a few hundred primers and it will play with your head.
I do remember wondering if the weight variability was to do with the absence/presence of wax, rather than amount of priming compound, but short of having a way to measure total heat output, it's a question I can't answer.

[KHGS]

I have a very simplistic approach to primer seating, not suggesting thatI am correct, but I uniform my pockets and seat my primers by feel. I like to feel the primers bottom out in the pocket. I did an inconclusive test on 210 versus 210M and I felt that std 210’s were as good as (or better) than 210M’s. I like CCI BR2 primers too, but I get lower SD’s with 210’s. These days we have to use what we can get……….Indian primers anyone?
Keith H.

[John Weigel]

One of my team mates has acquired the Indian primers an has agreed to giving me some to experiment with. Will report after, re weight consistency and head to head comparison to 210Ms and BR2s for speed and accuracy at traditional seating depths referenced by point of crush and both sides to see if relative accuracy nodes appear. The only early word I have heard is that they have relatively hard cups.

[ned kelly]

G'day All,
I uniform my primer pockets with the K&M tool, I clean my primer pockets with the same tool and if you are running high pressure loads you WILL see brass removed as the brass sets back when cleaning.
I also use the Sinclair priming tool and go by feel
You also must NOT over FLS you cases and induce excessive head space. Any gap will rob energy from the firing pin strike as it pushes the case forward into the chambers shoulder. I want ALL the energy from the pin to be used up on the primer, not pushing the case further into the chamber.
Seems to work ok over the last 25yrs of shooting.
Hope this helps
Cheers Geoff

[MarkS]

https://www.accurateshooter.com/technic ... -analysis/

[John Weigel]

OK, just clarified my best primer seating depth at 50m. The expected best result at crush plus two ‘clicks on 21st century hand priming tool. I only make this post because it twigs for me an error I made early in this thread: the typical best result isn’t 2 thous crush I mentioned, but 2 clicks on hand primer beyond contact of primer with end wall of primer pocket. I keep a separate 21st century priming tool for each rifle I’m working with with marked gradations indicating contact point.

IMG_2643.jpeg