Primer Seating Question

[J_McLeod]

I'm reloading 9mm and new to reloading. I used a Lee Auto Prime to seat 100 primers tonight, and measured every one afterward. Most were in the .003-.005 range, but about 10% were below .003. These I set aside and reseated until they were at least .003. Seating the primers went very quickly, but measuring them all is a pain. Is this something I should be doing, or am I overdoing it? Would it be unsafe to shoot rounds where the primer is seated at .001 or .002? How do some of the more experienced reloaders out there do it?

 

[ColtPythonElite]

Sounds like you are over thinking it. I seat 'em till they are flush or a smidge below. I don't do any measuring. I just run a finger over them. The Lee Auto Prime at full stroke seems to seat 'em just right.

 

[AnyMouse]

Do you scrape the gunk out of the primer pockets before re-priming?

 

[Hondo 60]

I agree with ColtPythonElite.
It sounds like you're over thinking it.

Just seat 'em til they won't go any deeper.

 

[twofifty]

JM - After priming 100 cases, you've probably developped a feel for how much pressure it takes with the AutoPrime. The right depth is when you feel the primer bottom out in a clean pocket (i.e. from brass that was tumbled clean). You will feel the resistance build then all movement stops, at which point you stop pushing on the AutoPrime's lever.

As ColtPythonElite said, to check you simply run a finger over the case bottom. Oddly enough, with a bit of practice, your thumb will tell you if a primer is proud, flush, or seated below flush. Proud is dangerous, flush is good enough, slightly below flush is safer and better.

You were cautious and measured your work, which is good. Once your thumb is 'trained' through repetition it will reliably detect differences as small as .002". You'll be able to quickly swipe the case bottom and know how well your primers are seated. Make sure to check each one.

btw, I've not heard of many folk individually cleaning HG primer pockets, as long as the brass was tumbled clean. The opposite is true for rifle cases.

 

[GLOOB]

You can't seat a primer too deep. So if you're getting some that are just barely flush, seat 'em all a little harder so you get some extra cushion. Even if they're slightly flattened, they're still good. I use a ram, and I go nice and gentle to feel if the primer pocket is loose. As soon as I verify good tension, I stop trying to feel. I don't care beyond that. I just squeeze the lever hard.

Final check: if you use a single stage press, try using a flat tray for a loading block. It's all you need for short auto pistol brass. Once you've loaded the tray, give it a shake. If you have any proud primers, the brass will wobble.

 

[Steve C]

Primers need to be seated into the bottom of the pocket. You should be able to feel them bottom out. As long as they are not higher than the base of the case you are fine. Failure to seat into the bottom of the pocket will result in misfires. The misfired rounds will usually go off when struck a second time by the firing pin as the first hit seated the primer to the bottom of the pocket and the second sets it off.

 

[ArchAngelCD]

Looks like there's nothing left to do here!

 

[Walkalong]

Run your finger or thumb over them after you prime them. Anything that is not above flush will pretty much be OK. Stop being so careful priming them and just seat them good and hard.

with a bit of practice, your thumb will tell you if a primer is proud, flush, or seated below flush. Proud is dangerous, flush is good enough, slightly below flush is safer and better.

I would have to agree. Some would say flush is not good enough, but I have shot thousands of pistol rounds where the primers were flush only with zero misfires or problems.

If I cleaned primer pockets in pistol brass, perhaps fewer would be flush and more would be below flush, but I only clean pistol PP's for ammo that is to be set aside for a rainy day.

 

[cfullgraf]

I agree with all the comments above. Flush or a it below is just fine.

I prefer to tumble my brass after resizing in part to clean the crud out of the primer pocket.

It is just one of my reloading idiosyncrasies and certainly not required.

With the Auto Prime, I squeeze fairly hard without plastically deforming the primer's lever. I seat the primer gently, for lack of a better term, so that if primer not lined up with the primer pocket, I don't crush the primer. Then give it the final squeeze to make sure it is fully seated.

After a time, you will get the "feel" and primer seating will be a breeze.

 

[JimKirk]

I prime with the Forster CoAx press priming system... it will seat them .003-.005 below flush, which is what the primer makers call for them to be seated. Unless there is something in the primer hole, there is no reason a primer should not be seated that way. After hundreds of thousands primers I've seated, I have had only one to fail to fire.. a broken firing pin. Once you get the hang if it ... you don't even have to feel ...you can look and see if a primer is high or low. Seat'em like they are called for and you'll have no problems.

Jimmy K

 

[winchester1886]

I always clean the primer pockets.I use a cordless drill and a wire brush pocket cleaner from RCBS. I have the time and I don't mind.

 

[cheygriz]

All primers should be seated to the bottom of the primer pocket. ALWAYS!

And don't waste your time measuring them. They will vary because the depth of the pockets varies.

 

[Doug b]

I got into a primer depth discussion when I first joined this board, it got pretty heated.So I proceeded to investigate.

I found that primers that felt flush by my fingers were actually .002" to .003" below flush.Primers that felt below flush were .003" to .005" below flush.Primers that were seated to flush actually felt high and high primers were obvious.

Again this is by my feel your results may very.

 

[Funshooter45]

So how do you actually make the measurement to determine if your primer is 0.001" versus 0.004" below flush? Like most everyone here, I look or feel to make sure that they are at least flush, hopefully just a "smidgen" deeper than flush. But I couldn't tell you if they are exactly 0.003" or 0.005" deeper than that.

 

[Doug b]

I used the tail piece on my Mitutoyo Absolute caliper,not the best depth gage but with a little work you can get a good measurement.Now I use Jim's method a forster co-ax .004" to .005" every time without fail.

 

[cheygriz]

There is no reason to even care how deep they are if they are seated to the bottom of the pocket! So why measure???

 

[JimKirk]

Measure with one of these ... found on evilbay, pawnshops, yardsales .... fairly cheap ... even new ....

http://www.grizzly.com/products/Depth-Micrometer-0-4-/G5622

Jimmy K


But like anything else ...you can sink some $$ into one too!

 

[J_McLeod]

I've been using the little rod on the end of my caliper. Put it on the primer, then push it until the rest of that end of the caliper is against the case.

I cleaned all the primer pockets by hand before priming.

 

[winchester1886]

If I have to start measuring primer pocket depth that's the day I'll quit reloading.The only time it didn't go bang was on my turret press when I was in a hurry.I seat the primer to the bottom and it wont go any deeper.Enough said.

 

[MEHavey]

Don't over-think this.

Put a straight-edge across the base of the case.
If you can see any daylight between it and the primer, you're good to go.




BTW: the biggest safety issue with short-seated primers comes with autoloaders having floating firing pins. (M1, M1A, AR-15) etc.

 

[DBR]

You can also check for high primers by just standing the cartridge up on its base on a smooth surface. If it can rock at all the primer is high.

 

[LiveLife]

I just run a finger over them.

Yes, this is a good test to feel the primers seated just below flush (about .004" below) and don't need to measure.

Maybe a picture is worth a thousand words - these were hand primed 40S&W cases with Lee Auto Prime. I didn't clean the primer pockets. Primers are PMC SP.