What is it? ---.405 Spotter experimental by FA

Any ideas what this is?

case L. 1.447"
rim .470"
belt .491"
head .466"
inside mouth .407"
neck .453"

Bruce, this is a short cased .405 Spotter experimental by FA. The open washer secures a perforated disc designed to regulate the flow of combustion gases (high-low pressure system).

Hi Bruce - sorry that I’m late for the game…

Fede has already answered your question (of course), but thought you might like to see a couple of other variations.

The ring/band was used to prevent the perforated disc (called a metering plate) from being blown down the barrel. This disc regulated the flow of gas very well. I’ve been told that shot to shot that the variation was only 5 f/s.

It is somewhat of a complicated case and ultimately not necessary as later versions went without. The same can be said for the plastic driving band. The middle round is the common one. It does have a tracer element. # 5 is a proof and the last one was a Winchester design.


Paul, thanks a lot for sharing this image. Could you tell us the case lengths?

I had a couple of them and didn’t know what it was. Thanks for the response.

Hi Alex,

The short case is 36.7 mm
The medium case is 43 mm
The long case is 50.5 mm


Paul, thanks a lot!

Paul, great picture, thanks for sharing. Those made from modified Cal. .30 cases are also found with a case lenght measuring 63.5 and 66 mm, but I don’t have a picture.

This one is a 5-flechette load (under the black cover), headstamp is “SUPER SPEED 30-06 SPRG” & it has a 63.5mm CL.

Is this what your looking for Fede? Was not aware these were also loaded as spotters.

Pete - that was exactly what I was going to ask Fede also. I couldn’t place it. I spent some time ruminating about it and checked my pictures from Woodin Lab, and viola:



Fascinating subject, great information and great pictures!

For those of us who are uninformed would you please explain what all is being shown in your last picture?

Its a very steep learning curve on my part.



Last but not least, for which weapon system were these spotters developed?

Hi Brian - this last picture shows some of the rarer variations of the Winchester made 10mm sub-caliber round. Pictured are both projectile and case length variations.

Alex - I have never learned for what weapon system these were developed for. Yet another question likely to be answered when HWSIII is published!


Paul, we are looking forward to this then.


Thanks for the reply and as you and EOD suggest hopefully HWSIII can shed more light on this.


Paul, thanks for posting this picture, these were the prototypes to which I meant.

Here is a previous discussion about this cartridge and its use: viewtopic.php?f=8&t=12376

Thanks, Fede. I thought you’d come up with a picture of the system.


Fede, thanks! I totally forgot about this thread.