I emailed 21st century and asked why their tool was adjustable for depth when the reloading manuals clearly state that a primer must be seated fully on the bottom of the primer pocket.

I got his reply today.

He said their tool adjusts so that the user gets the best feel "WHEN THE PRIMER HITS THE BOTTOM OF THE POCKET"

So all you guys using adjustable depth priming tools to seat primers to the same depth regardless of pocket depth and are not seating the primers on the bottom of the pocket are priming incorrectly.

Motor

Motor1, I also recall Sinclair's instructions to seat beyond just touching down on the bottom of the primer pocket.  Sinclair says you want a little "crush", just a soft touch beyond bottoming out.  Although a somewhat vague, non-quantitative description, all became very clear to me once I used their tool.

I do believe you want, at the very least, to touch the bottom of the primer pocket.

I think a variable-depth primer seating tool is a good thing.

There is a fairly wide range of "in-spec" primer heights.  Different manufacturers' primers wind up being different heights (that's total distance from outside of the cup to the top/front of the anvil's legs) for a number of reasons.

In this article about the relationship between primers (and cup thickness) and chamber pressure, you'll find a chart with the specific cup depths of a number of common primers.  They vary by more than 0.008" from one brand to another, and even vary more than 0.005" within the same brand and primer size.

This is one reason why it is sometimes challenging to just go by feel.  Add to that the variations in primer outside diameter and variations in primer pocket diameters, and you can wind up with more or less seating resistance before you get the primer bottomed out.

I started thinking about primer seating depth when I started getting into reloading Berdan primed cases.  The anvil is part of the case, so you can't go by feel; you have to seat for a specific depth of the primer cup below the case head.

With Boxer cases, if you uniform the primer pockets, you can actually calculate how deep below the head your primer cup needs to be for the anvil legs to contact the bottom of the pocket.  Measure the depth your uniformed pockets are, the height of your chosen primers, and subtract height from tenth.  Once you do that, you will know whether or not you're seating your primers properly.

I'm perplexed by your conclusion.  From the discussion of dimensional variations, you proved a point about not seating to a particular depth, as it does not guarantee the primer is seated properly.  

From that same discussion, I conclude that seating by feel is the ONLY way to go, as dimensions don't get you where you need to be.



You also mention variations in diameters causing differences in "feel".  While true, once the primer is moving, it is very evident when it bottoms out.  At least it is when using the Sinclair tool.

GHPorter, I'm not trying to say you are wrong or be argumentative for argument's sake, I just have a different perspective on the info you provided and thought additional discussion and  might be useful.

I can kinda see how that came across as not-so-clear.

I'm pointing out that knowing your depth may be important, and that a variable depth tool, adjusted to suit a particular primer/case situation, is a Good Thing.

I'm not shooting bullseye or anything, but I do have a tendency to damage tools.  I have a pretty strong grip, and if there's a question about whether I'm encountering resistance because of the interference fit between the primer cup and the pocket, I really like knowing that I'm not crushing the primer when I seat it.

Interestingly, seating primers on my Hornady LnL AP gives me a better "feel" for the difference between seating resistance and fully seated.  I think it has to do with how clear it is when the press handle isn't all the way forward yet...  That's harder for me to feel with my hands on a manual tool for some reason.

Yes, press-mounted primer seaters get a bad rap.  I like the priming set up on both my Dillon 550B and my Redding T-7.  

The Sinclair is slower than the Dillon but faster than the T-7* and the Sinclair is clearly superior to either.  If you consider you are able to use it at the time and place of your choosing (e.g., while wife watches Call the Midwife) rather than only while at the reloading bench, there's no lost time.  As such, perhaps it is the fastest of them all.



*  I can only feed one primer at a time into my T-7 because I didn't buy the optional "Slide Bar Automatic Priming System".  If I didn't have the other press and the Sinclair tool, I would almost certainly have purchased it.

You really can't blame the tool maker for not fully explaining how to properly seat a primer although according to Trollslayer at least Sinclair does. They assume you already know how.

But in this age of internet trained reloaders vs book trained it seems people are assuming too much. The depth adjustment on these priming tools are basically for ergonomics reasons and nothing more.

After many years of priming with a hand held priming tool I can easily see where such an adjustment could be helpful. These tools typically don't have a linear torque curve. Meaning the ratio between lever movement and plunger movement is not constant.

So if for whatever reason your primers are bottoming a few thousands of an inch higher than whatever brass or caliber you did last or of course lower, this can have a significant effect on where the lever is when the primer hits bottom. And on the amount of leverage the tool has at that specific location.

So tools like the ones mentioned above allow you to adjust the ram (or plunger) so you can have the primers hit bottom with the lever in the same location. This greatly improves the feel and feedback to the user.

Of course being well made helps a bunch too.

Motor

I am still a Noob I quite like the RCBS hand priming tool.. used my fathers a lot and had no issues.  Finally graduated college and got my own gear.  picked up a Hornady hand priming tool and it sucks.  Set up is strange and the primers are constantly rolling sideways on the short trip from the primer tray to the push rod.  I think it will be getting sold off soon and ill go back to an RCBS

If one uses the same brand of brass or brass from the same lot, primer pocket depth is pretty consistent. At least, that's what I've found. Once in a while, you'll find a pocket too deep or too shallow, but not to the point the case should go in the salvage pile. For those who use mixed range brass, there isn't much consistency. I wouldn't use a tool again that did not have an adjustable depth with good "feel" for when the primer is fully seated.

Yes, the setup is WAY different from the RCBS, and as I noted, the ergonomics are pretty different too.  

The primer rolling thing is fairly easy to manage by making sure they're all flat and then getting the primer tray cover on all the way at all points.  It's not obvious that the cover isn't fully seated until you really get it down everywhere.  That's an "ah ha!" moment.  After that, it works fine.

I will say that the Hornady tool let me overseat primers fairly easily, while the RCBS tool makes it not so easy - although you can do that with any hand priming tool if you work at it!

GHPorter,

What exactly is "over seated" ?

Reloading how to manuals and according to Borderpatrol even the Sinclair instructions say a light "crush" is desirable.  

Motor

A "light crush" is fine, but here's enough leverage in the Hornady tool to HARD crush a primer if you aren't careful.  Not that those I did this with failed, but the cups were severely flattened, which I didn't notice until I had about 50 cases primed.  I don't trust a primer that I've flattened that badly...

I usually counsel people to NEVER ask what is "best" on a forum because what you will get is the opinions of people as to what they would buy for themselves if they could spend your money.  Instead, always, ask what someone would buy with their money and ask them to explain why.

I would recommend the RCBS hand priming tool.  This is because 1) it works, 2) it uses standard shell holders, and 3) it is backed by RCBS impeccable customer service.  I bought an RCBS hand priming tool back in the 1980's.  It is still working today.  If I had to replace it, I would buy another RCBS based on my experience with what I have now.

This was probably the "best" reply yet on this topic.

BTW: GHPorter, understood. I wouldn't have thought a hand primer would have that much leverage.

Motor

Between the leverage - the lever lets you apply considerable pressure because it puts your ring and small finger on the longest part of the lever - and my stupid heavy grip strength (160 pounds gross grip is not unusual for me), yeah, I can mess up primers.  

F(fifth)PNI

While the universal portion isn't totally accurate (won't hold a piece of 5.7x28 brass) I've used mine for several thousand .308 and 7.62x54R destined for loading on a single stage and been nothing but satisfied.

I presume my small primer adventures for 6.5x47 Lapua will do just as well.