7.62 nato primer info

I can’t find any info on this small primer in a 7.62x51 NATO cartridge.
It has a sticker that says “Experimental Primer” ?

Maybe a stupid question but is this a life cartridge and do we see an actual primer?

I always learned that winter and ball powder needed primers with as much “OOMPH” as they could master.
Unless that petite primer holds explosives i do not think it would pass muster in NATO ammo!

Heres a list of RWS primers and their brisance
The right to middle “small pistol” should of course be “small rifle”, a typo in the book from where it originated.

Chickenthief, surprise or not but primer compositions are HE (high explosive) in it’s best sense (just way more sensitive).
So the smaller a primer the less the “OOMPH” as you say.

Hi Bruce,

This is a Bloem primer and were used for action test times.



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OK, I am leaving my ego on the shelf, :-) and I have to say I am confused due to my lack of my knowledge on this item :-)
For other others out there like me .
What is the action time test ? and why the smaller primer ? Is this the action time in a machine gun or semi-auto ? or a high pressure proof test ?
Thank you to anyone, in advance, who can enlighten us in advance for helping us with little knowledge on this item.

“action test times” ?

Thanks Paul.

Paul, you stated action test times, is that the time for a machine gun to cycle ? or proof test ? I could assume and I shouldn’t assume, as it normally proves me wrong. :-)
Beautiful sectioning job!

Sorry, I don’t have the details. I’ve seen a box, but can’t find the picture.


Previously discussed here

Picture of box in the thread.


Thanks Ole!

Thanks, I was just wondering why you would not use regular ammunition to test an action, unless if is a high pressure proof test. A very interesting primer. Thanks for sharing.

For those of us that don’t know, the question of “What is an Action Time Test” and why does it require special primers in the cartridges used for such tests(?) is not answered. I would like to know. Is it in HWS Volume III? I admit to total ignorance about this particular terminology (and many other things as well, of course). Does anyone know?

John Moss

Action time basically is the time between the firing pin hitting the primer and the bullet uncorking the muzzle. In interior ballistics several definitions exist. Action time became important with the use of synchronized machine-guns fring through the propeller. A typical maximum acceptance value is 4 milliseconds, while an ordinary round needs about 1.5 milliseconds.

No doubt they had some good reason to build this experimental cartridge, but the purpose of this special primer is not clear to me. Maybe the much smaller amount of priming mix has a smaller variation in the time to go off and allows more precise timing of the propellant starting to burn.

Thank you, I had not heard the term “Action Time” before now.

I’ve put the photos of the original Olin drawing, with their “Bloehm” spelling for this primer back up see: Bloem Primer?

Apropos of “action time” I always thought it was the time lapse between sear disengagement of the firing pin , primer ignition time, powder combustion time, and bullet in barrel transition time to exit muzzle.
Important parameter for propeller synchronized guns
–up to WW II- AND NOWADAYS inthe realm of very high RoF Gatling type guns driven by electric motors.

Doc AV

Some of the problems in gun synchronization got omitted by using electric primers.

I was just going through a NATO STANAG from 1982 defining the requirements of a “NATO standard” 9x19mm cartridge and Action Time was one of the required characteristics. I do not know how ammunition is tested to demonstrate it meets this requirement.


Doc AV, this is why I wrote “basically” and mentioned different definitions.
What you describe is including “lock time” into the picture (a term used by Hatcher).