I'd like some opinions about something I had happen today with recently handloaded 357 Magnum pistol ammo.

I was shooting my Ruger GP100. My friend had his Ruger Blackhawk (both in 357 Mag).

I had loaded virgin Winchester brass with CCI 500 small pistol primers, 13.5 grains AA5744, and a Hornady 158 grain XTP bullet.

About 5 to 8% of the ammo showed a very light primer strike, and didn't fire on the first hammer fall. Putting them back into the chamber and pulling the trigger again got 100% ignition.

The only thing I can think of is how I primed them: used an RCBS hand held priming tool (which is almost a copy of the Lee priming tool).
However, I didn't have the smaller rod meant for priming small pistol cases, and used the standard rod that I use for everything from 44 Mag to 458 Lott.
(The rod makes contact with the individual primers and forces them into the primer pocket...I must have lost the small rod somewhere along the way).

However, I was careful not to exert too much force in seating the primers, and in looking at the primed cases carefully, I can't see any deformity of the primers, and the primers that fired and the ones that didn't don't seem any different....except of course the the primer strike (indentation) is much, much lighter on the cases that didn't fire.

Since this was happening with 2 different firearms, it must be something to do with how I seated the primers. I have a hard time believing that 8% of a tray of primers could be out of dimension.

All cartridges and cases were of the same length, and all the cases were virgin brass sized, trimmed, deburred, cleaned, belled and then loaded.

Ever seen this happen?

Garrett

The "Anvil" of the Primers, on the ones which did not fire, were not touching the bottom of the Primer Pocket. Amazing that many of them still worked at all.

RCBS will send you a new Small Punch if you ask them. Great folks to deal with.

What Hot core mentioned in his own inimitable way, was that you did not seat the primers deep enough. When you do this, the primer will move forward under the pressure of the firing pin strike, and the firing pin will stop and rebound. You'll have what looks like a light strike. The second attempt to fire will most times be successful, as you have re-seated the primer with the first strike.

This is not an uncommon event these days as it has become fairly popular to use hand priming tools in the mistaken (and encouraged by those who make and sell hand primers) belief that you are somehow going to "feel" the primer seat better with the hand tool.

This was a hot topic among BR shooters some years ago and was the cause of the invention of the K&M hand primer, which is the only, as far as I know, hand priming tool that has a dial indicator which shows you EXACTLY where you just seated that primer. BR shooters almost to a man, prefer that their primers be seated all the way to the bottom of the pocket and then a bit more, what is called a "crush" of .001" or .002". Match primers are usually all the same height give or take .001" but standard primers are allowed to vary a lot more than that, so "feeling" primers seat is not a cut and dried process for them.

I had the opportunity to participate in a test of how well experienced handloaders really could "feel" primer seating. Five of us were allowed to use a Bonanza (now Forster) co-ax press to seat 100 primers in 100 .30-06 cases. Five were allowed to use a K&M seater without the dial indicator. Then we switched. The hand primed cases were miserably un-uniform. The press seated cases were slightly better. Before those who are not familiar with K&M tools disparage the seater, let's note, that there is NO better primer seating tool, and when the dial indicator was used all 500 primers were seated to such a close tolerance that you could say they were 99% perfect. The test was published in PS magazine about 1992? I can't remember exactly.

DO I NEED PRIMERS SEATED THAT PERFECTLY?

Not for anything but rifle match loads. Still, the problems with grossly mis-seating are as you have experienced. If I were you, I would seat a few primers and check the depth, which can easily be done with the butt end of your calipers. If you can then develop a feel for when the primer is at least bottoming out, then well and good. If not, go back to seating on the press.