Measuring Primer Seating Depth

EricBu said:
Which is fine...but not relevant to using a tool to measure what you have. You're using exceptions to justify not measuring to validate a published specification. Like I said, you do you. Measure, don't measure...whatever works for you. What I'm trying to do is demonstrate to new users, or to people that are having challenges with certain types of primers...a method to check depth when they think it's seated deep enough based on feel, when in fact it is not. This was a post to demonstrate one method of measuring primer seating depth in a definable and useful way for folks who may not know how to, or that they in fact already have the tool to do it.

Again, to emphasize, regardless of all the noise here...if you cannot measure a minimum of a .003 primer depth, then your primers are not seated deep enough. Square pocket, round pocket, blue pocket, the number of molecules on a pin head...whatever argument you want to make...doesn't matter.

Btw, you hyper sensitive touch guys....You realize people aren't born reading brail right? They have to be taught the meaning of what they feel...which is why telling people how great your sensitivity is...ain't real helpful to the guy trying to figure out the problem with his reloads.
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It's good to teach & learn multiple methods. Thanks for providing yours.

But, for those of us who only took one shop class in high school 60 years ago and then learned everything else scraping our knuckles on our cars, saying "just take your calipers and do this" isn't all that simple. (Gee, thanks, if I was as coordinated as you and didn't have arthritis, that's what I'd do.)

But, I also completely agree, telling someone new to this or that to "feel" when something is right or wrong, is like a foreign language.

But, they're both valuable and mutually supporting.

Our brains are amazing things and some of us can develop the "feel" of something long before we can master the physical manipulation of a tool to the necessary level of precision.

As my post #4 indicates, I tried the caliper method with apparent success, but I'm telling you it wasn't all that easy.

Long (years) before that however, I had developed an eye and feel for a good workable example, memorized it, and could spot a bad example a mile away. No, I wouldn't be able to provide numerical measurements, but I'd just know.

Now, I can do both.
 
I can feel some primers bottom out, some not so much, kind of depends on the combination involved.

Everything I seat in bulk with a hand primer gets seated hard.

My PRS ammo primers are seated in a hand primer that takes one primer at a time. I can usually feel these seat, but I changed from that to setting an adjustable hand primer set for that primer/brass combination and just seat them to the stop, turn the case 180 degrees and do it again.
 
I uniform primer pockets on my precision rifles, hunting rifles, and pretty much everything I don't load in bulk like 357, 45 Colt, and 38. In fact I'll trim, uniform, neck size, everything and etc (OCD) on those rounds to make them as accurate as possible. I load 9mm, 45 ACP, and 308 in bulk for target and 3 Gun. I load 500 to 1000 rounds in bulk. I don't do any of that to those rounds. It's just too time consuming, and in my experience, unnecessary. It just doesn't make that much of a difference for those purposes. If I do my job being sure to seat the primer, my Springfield 45 1911s never have had a FTF regardless of the primer I choose to use. If I have an issue where I believe that primer seating depth is suspect, I'll measure the primer seating depth or reseat the primer (not a good idea on loaded rounds). That is how I discovered the issue with Russian primers as I stated in another thread and that some may be having on the SA primers. Regardless, I still primarily seat primers by "feel" and visual inspection, and the "feel" is not the same for all brands of primers. Not real technical but with the exception of what I mentioned above, it has never been an issue for me. I do agree that new reloaders need and should follow a guideline of some sort and measuring in the manner suggested by the OP is a good one. But this is all my opinion based upon experience that is not highly technically based. Heavens, I learned reloading from Tubbs VHS videos I got from Cabelas. Later, others in my world filled in the gaps with information and data that at times would make my eyes gloss over.
 
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Lets be honest here folks....if there had never been a primer shortage, and we were all still buying US made primers for < .01 ea....this discussion would have never happened. Because quite frankly, seating to feel with US primers works a solid 99% of the time. It was only the influx of metric primers that this became an issue. I recall dealing with it the first time...maybe during the great primer shortage during the Clinton years, when I bought Murom primers, if memory serves. The importing of metric primers has only increased in the ensuing 25 years or so. That and the variety of brass, and new types of brass..and brass made overseas, and primers coming from what, 5 different countries now....there are a lot more variables, which means a lot more opportunities for pain. We should all strive to develop and pass on ways to find and fix things like this BEFORE range day, and as part of what we talk about when bringing the youngest generations into the reloading fold.

Edited to add...I just realized the first time I came across this. When I was stationed in GE in the 90s, and the closest place to buy reloading supplies was in the Czech Republic. I bought CZ primers, and had a heck of time with light strikes in 38 and 357 revolvers, and my 1911. One of the guys in the Kitzingen shooting club told me why.
 
EricBu said:
A customer brought me a partial box of 45 Colt high performance defensive boutique ammo and a Taurus revolver a few weeks ago. His issue was light striking primers, and he was concerned it was the gun, but wanted to have it checked before he bought more of this particular ammo, or sent his revolver back to Taurus. So I broke down a few rounds to see what they were about. It was apparent that the company was using Ginex primers after I decapped a couple of pieces I'd broken down. So I immediately busted out my calipers and checked the seating depth...because metric primers are often not seated deep enough. I thought, you know....this would be a good time to take some pictures in case there are folks out there who don't know how to measure primer depth. Slipped my mind until this morning, so here it is, better late than never. Of course, this is just one method, there's lots of other ways, some much more accurate, some less so. But almost all reloaders and handloaders have a dial caliper, and almost all dial calipers have a depth gauge...so this is likely a method that virtually everybody can use right away without additional expense.

Now, we know there are dozens of folks out there groaning...."you don't measure, you seat until they bottom out"....well, sadly those folks are wrong. Why? Because a metric primer "feels" bottomed out, when it isn't. "well, it just needs to be flush"....no, sorry, again....wrong. Depending on which reloading manual you own, the specification for primer depth is from .003 to .008. Myself, after 35 years of doing this, have determined that .003 is the absolute minimum depth to function reliably 100% of the time in all properly functioning firearms, but that's MY OPINION....most books seem to lean towards .004 to .005. Edited to add, the other reason to make a habit of QC'ng your ammo and checking primer depth...is when you get a piece of brass that's getting long in the tooth....you'll catch it here as well...you may see your primer seated .010 or even deeper...because the pocket has streatched or malformed. This is just as bad as not seating deep enough.

So back to the story...

This particular boutique ammo used Starline brass. New Starline brass can have relatively tight pockets, leading me even more to the conclusion the problem was seating depth. So I took a couple of pieces of brass I'd broken down and checked them out, then ultimately measured all of the rounds in the partial box. What I found:

Out of 10 rounds, 2 were .001 proud (above flush), 6 were .000, and 2 were .001 deep. None were within the specification above. How did we measure this?

1. The butt of your dial caliber has what's called a depth gauge. This is a slender metal rod that extends out the base of your caliper at the same measurement as the gap in your calipers. By butting it up against a primed piece of brass, you can extend that depth gauge, and get a reading how deep it is below the base of the caliper.

View attachment 1198898


2. I like to push the mouth of the piece of brass up against a flat surface, I loosen the friction lock on the caliper, extend the depth gauge, line it up with the center of the primer, and push the caliper forward and take the reading.


View attachment 1198899

3. I usually rotate the brass and take the measurement several times. The overall all measuring process looks like the last pic below. You'll note that the measurement is .001, not deep enough. You want a reading of .003 minimum, deeper even depending on your gun. Only once you've measured primers and verified the depth, can you start looking at other things...a primer with too hard of a cup for your application, a gun with a problem, or a bad batch of primers. Relying on feel....then everything else is just a guess, unsubstantiated claim, or excuse.

View attachment 1198900

Hopefully this helps somebody out. I did this because I was working on the related task above and it was timely, and I don't know that I've ever seen anybody put pictures up on how to use the depth gauge on THR before.

So what happened with my customer? I called the ammo company, talked to one of their folks. They'd actually had another report from the same lot, and knew of the issue. I gave them my customers address and they shipped him two new boxes of ammo, and they functioned perfectly in his gun, and he was super happy, so I folded up my cape, put it away until next time...and had a celebratory ice cold adult beverage.
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Nice write-up! Great pictures too. The more I read about imported primers the less impressed I get! I wonder if the Ruag primers that we are starting to see have these issues? Plus 1 on the adult beverage!!!
 
lightman said:
Nice write-up! Great pictures too. The more I read about imported primers the less impressed I get! I wonder if the Ruag primers that we are starting to see have these issues? Plus 1 on the adult beverage!!!
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Thanks for the kind words...I will say this about the metric primers: You cannot beat them for accuracy on long range precision stuff, especially at their price point. My goto for my 338 LM, and heavy .308 has always been Federal LR Magnum. I will tell you straight up....to get Ginex LR preloaded (seated to bottom and anvil loaded) on Lapua brass is a bit more work...you have to be religious on cleaning the primer pocket, and you have to put some serious muscle into your press. A bottomed out Ginex in Lapua brass = .008 below flush. When you get there, the accuracy is identical to Fed LRM...but the real gain comes about the 5th loading of that brass. The Fed primers start to open up the groups at that point, and when you seat them, it's starting to feel like throwing a hotdog down the hallway. At the 5th loading, Ginex start getting easier to seat. I get the same groups with Ginex after 8 or 9 loadings in Lapua brass as I do with Fed in the first few loadings, all other things being the same or equal. So, there is merit there. That and the fact that Fed LRM are unobtanium, and I can get LR Ginex for .05 ea right now. Yes they are a pain, yes it takes extra effort to seat them, but I got them, and I've never had to slack up on my shooting of anything that requires LR primers, because they are pretty easy to get, even now.
 
EricBu said:
Thanks for the kind words...I will say this about the metric primers: You cannot beat them for accuracy on long range precision stuff, especially at their price point. My goto for my 338 LM, and heavy .308 has always been Federal LR Magnum. I will tell you straight up....to get Ginex LR preloaded (seated to bottom and anvil loaded) on Lapua brass is a bit more work...you have to be religious on cleaning the primer pocket, and you have to put some serious muscle into your press. A bottomed out Ginex in Lapua brass = .008 below flush. When you get there, the accuracy is identical to Fed LRM...but the real gain comes about the 5th loading of that brass. The Fed primers start to open up the groups at that point, and when you seat them, it's starting to feel like throwing a hotdog down the hallway. At the 5th loading, Ginex start getting easier to seat. I get the same groups with Ginex after 8 or 9 loadings in Lapua brass as I do with Fed in the first few loadings, all other things being the same or equal. So, there is merit there. That and the fact that Fed LRM are unobtanium, and I can get LR Ginex for .05 ea right now. Yes they are a pain, yes it takes extra effort to seat them, but I got them, and I've never had to slack up on my shooting of anything that requires LR primers, because they are pretty easy to get, even now.
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Tula for me. Right around Y2K. They worked so well in my Garand I kept buying them even after the shortage ended. There was a learning curve to seating them properly but that was a long time ago and the workarounds I learned then are now my SOP - thus the habit of uniform primer pockets and inspecting brass with loving care. 🥰
 
I’ve used the caliper depth rod for measuring lots of depths, including primer seating depth. Anytime you have a reasonably flat surface to rest the beam on it should give you a reasonable reading. The beam’s got to be perpendicular to that flat surface in two dimensions or the reading can be off.
This is a QC step when I’m reloading whether it’s an SS or progressive press.
If I’m priming on my RCBS Rockchucker, I find if I try to rip the press off the bench, primers usually get seated. I also use a Lee bench primer which is a bit easier.
On the LNL, it’s a forward push on the handle as far as it’ll travel.
On the Dillon 1100, there’s a tappet mechanism to adjust seating depth as all operations are done from a “pull” only.
I find if I’m loading range brass on a progressive, primer seating depth can vary from .001 to .006, and there are no FTFs KOW.
 
CQB45ACP said:
Thought it was a trophy.

And the Instrument for most accurate primer depth goes to...
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I appreciate quality tools but that could be done SO much cheaper and compact. Like an indicator with bushing attached so the plunger only protrudes .030" or so. Zero with anything flat then put the case directly to the indicator.
Calling Lee to sell one for $60 tops. (of course I"m thinking of pre plandemic, $100 now :thumbdown: )
 
That’s a nice looking tool. I heard he who dies with the most tools, wins.

Here’s another one/company that likes to catch your eye:

www.woodpeck.com

OneTime Tool - Angle-Depth Gauge - Retired December 26, 2022

Woodpeckers newest OneTIME Tool takes a century-old machinist’s tool and updates it for use in the modern woodworker’s shop. For around a hundred years, machinists have relied on a device similar to our new Angle-Depth Gauge to measure small holes and grooves. We took the fundamental design...
www.woodpeck.com www.woodpeck.com
 
Actually based on this discussion wouldn't a better tool be an "AYSIFSROTD" gauge? (Are you sure it's fully seated regardless of the depth)

Would look through the flash hole from the inside or some other way.

For the other type to work, you'd have to be pretty sure your pockets are of uniform depth before you seat a primer. Now that sounds like a winner to me.
 
I get less than one strike without firing per year (thousands of rounds). I load a mixture of large and small, rifle and pistol, semi-auto, bolt, revolver and SS, hammer fired and striker fired.. The majority are revolver and pistol on a progressive press with unprepped mixed headstamp brass. I'm not going to put more thought into primer seating depth beyond feel, except for precision rifle stuff with prepped pockets.
 
Had some 357 mag primed in the loading block the other day when I started reading this thread, so when I got back home I decided to take a look.

I prime on press with my RS5, getting primers at least below flush isn't all that hard, but taking measurements I found that just below flush to my fingers is around .002", and primers seated to what I always though as "pretty dang deep" were in the .005"-.006" range.

It's food for thought. I haven't had any FTF with 357 mag and my Henry, but, the other week I did have a FTF with some 38-55, the very last round of the day actually. I let it sit about 10-15 seconds and then extracted it. Sure enough light strike. Loaded it back up and it went off on the second strike.

So I think next time I prime some of those 38-55 cases I'll take a measurement or two and get a better idea of how .005"-.006" seated depth feels in those cases and go from there.

I'll probably not get into the habit of measuring each one as I seat them, but getting a frame of reference with my fingertip will help to know if any need a little more pressure getting in the pocket.
 
I mostly prime on my single stage, and when seating a primer I "lean" on the lever a little bit. I visually inspect the brass and primer when I remove it from the press, and quite often the primer has a bit of a flat spot in the center. I've yet to have one fail to ignite, but I've only loaded about 5K rounds or so.

chris
 
E
ballman6711 said:
I mostly prime on my single stage, and when seating a primer I "lean" on the lever a little bit. I visually inspect the brass and primer when I remove it from the press, and quite often the primer has a bit of a flat spot in the center. I've yet to have one fail to ignite, but I've only loaded about 5K rounds or so.

chris
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Even with my now uniformed pockets which invariably are deeper, I still lean a little on the lever to ensure primers are fully seated. I actually tried recently to not lean, but reverted to it anyway due to muscle memory I guess.
 
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