US 20x110 HS Electric vs. Percussion Primer


In a recent thread started by Shotmeister on his Navy ammo can, the discussion evolved to the use of electric vs. percussion primers on US 20x110 HS ammunition. It seems that designations applied (M95, M96, etc.) do not differentiate the primer type used as various TMs list them as both electric and percussion under the same designation. In other sources I’ve found that, if anything, this is indicated parenthetically as, for example, “M95, Armor Piercing Tracer (Percussion Primed)”. This seems a little odd as there has been little restraint in tacking on additional designators to distinguish variations in loadings of most other ammunition. An exception that comes to mind is the designation of (Steel Case) for other small arms loadings when the case material is the only difference from the basic “M” number.

The other question that arose was in regard to interchangeability between primer types in guns capable of firing one or the other or both. As is the danger when I encounter such questions, I started thinking…

The German developments of electric priming were to allow improved synchronization of thru-propeller firing guns. Later US use of that technology captured during WWII was applied with bomber defense turrets in mind to keep gunners from hitting their own aircraft and also to balance twin gun mount firing vibrations. While I believe the electric primed German ammunition and the guns firing them were electric only, TM listings of some item’s applications seem to indicate the US may have seen some versatility in the situation.

Perhaps there is interchangeability to an extent in that an electric gun could be designed able to fire both percussion primers and electric primers. Provided an electric primer could withstand (and not fire with) an impact required for a percussion primer, this would be a workable situation. A percussion-firing gun would require exclusive use of percussion primers, as there is no electric charge present but an electric gun using electric primed ammunition could have all the mechanics in place yet withhold electric current and discharge as required.

The electric contactor of a gun designed for exclusive use of electric primers needs only to engage the primer enough to allow current to flow to the primer. I would guess in modern applications of extremely high fire rates the use of electric priming is to reduce the mass of parts that have to move very fast. This, I think, is seen in the example of a 20x102 fired case (shown on the right) where the fired electric primer is barely dented. While I don’t have examples of 20x110 HS fired cases from any particular gun, for fun I also showed an electric primed M96 20x110 HS on the left and a WWII vintage percussion primed version at center. Note the M96 is stamped “ELEC”.

Pardon the rambling, but these things happen…Would be very interested to hear any thoughts out there on the “same designation for different primers” thing as well as the interchangeability of electric and percussion primed ammunition in general.



Calling Mr. Williams. Mr. Anthony Williams.

Bettin’ he knows.

And here’s some of his info on the subject: … ing_20.htm

Scroll all the way down to the chart.


An interesting question to which I do not know the answer. I have never heard of combined electric/percussion primers before, my understanding has always been that the primers are of entirely different design and specific to their guns. However, I am not an expert on primer design so I can’t say for certain that a hybrid primer is impossible.


During my Royal Navy service there were dual electric/percussion primers in existence on some cartridges. No small stuff like 20mm as far as I know, just 4.5inch and above. The electrical contact was also a plunger which would fire an internal percussion primer if struck firmly by a percussion striker. They were complicated and I know of no current use of them.



There is at least one hybrid primer in regular use with the ammunition for the Russian 125mm Tank gun D-81. The primer there is the GUV-7.
I think I had seen others as well but do not remember the details.


Thanks all for your input on this.

I’m thinking the interchangeability (if any) has more to do with a “hybrid gun” rather than a “hybrid primer” and the workings of the M24A1 gun may hold the answers I’m curious for. TM 43-0001-27 seems to imply that this gun can use both percussion and electric primed ammunition. Got no clue how the electric part works so at least I might learn something from figuring it out…

Added: Figured I’d start with TM 9-2006. Ordered and on its way…

Thanks again,


In light of these two most recent threads on 20MMs(this one and the can one), are we redfining SAA as 20MM and smaller? That would make me soooooo happy. All you +/-.30/7.62 guys need to check out this bigger stuff. Very interesting with tons of variations, as noted. And colorful, for those so inclined(you know who you are).

Just glad these threads and jocular posts were allowed to continue without “interruption”. Muchos gracias el Moderator(s).

Just look at how “pretty” the bigger stuff can be.



Seems you’ve been busy rounding up some of the big stuff. Very nice!

While not everyone’s into it, I don’t think you should feel that this forum is not a place for the “over .50” items. It is ammunition after all! There is a lot of related technologies between the big and smaller types and I always figured any learning is good learning. (All I do here is ask questions anyway…)

If you’re real nice, they even let you post things on shotshells!

Perhaps you could give some details on your latest 50-60 lbs. worth of fancy colored ordnance you’ve aquired? I promise to restrain the jocularity.



Tell ya what Dave, as soon as I get the latest addition, I’ll post on the assortment of .50 cal link loaders I’ve acquired. Two of which came from Norway! An interesting story in itself. I try real hard to stay within bounds here and respect the limits and rules. Although Ray makes me write things I probably shouldn’t.
Got a nice assortment of older SAA a while back, just haven’t gotten around to the necessary photo shoot. Or even sorted them all to see exactly what I have. Still in the proverbial cigar box.
Soon as I get time(they’re wearin’ me down at work) I’ll work up that post.