Actual URL Link for the Video: https://youtu.be/sTdK1jqKV7E

What in the world is going on here?

4.7gr of some kind of powder seems like a 40S&W load to me. Winchester or someone please speak up on the thought process of developing this load.

Shadow what in the world is going on here?

I fixed the link for you...

Well after some study of the Winchester data and powder pics, I would say that the 4.7 - 4.8 grains will be WSL powder @ 950 fps 28,400 PSI
Sub sonic stuff was usually a result of contract ammo for special uses...like close quarter engagements by law enforcement agencies...Navy SEALS and FBI
Thanks for the pics and video!
Winchester older data;

Don't forget that the FBI commissioned a batch of 10mm Thompson SMG's years ago. And there were some H&K MP5's made in that caliber, also. Now, we all know that our government likes to give it's boys with badges some pretty cool tools. I have no doubt whatsoever that the FBI had suppressors for the Thompsons, and subsonic 10mm ammo to go with them. Can you just imagine???

So... I'm thinking a CMMG Banshee or Kriss Vector, a Gemtech or SilencerCo can, some of this ammo... the 10mm just might get house protection duty after all!

Quote from: woods_walker on December 01 2019 06:23:50 PM MST
Don't forget that the FBI commissioned a batch of 10mm Thompson SMG's years ago. And there were some H&K MP5's made in that caliber, also. Now, we all know that our government likes to give it's boys with badges some pretty cool tools. I have no doubt whatsoever that the FBI had suppressors for the Thompsons, and subsonic 10mm ammo to go with them. Can you just imagine???

So... I'm thinking a CMMG Banshee or Kriss Vector, a Gemtech or SilencerCo can, some of this ammo... the 10mm just might get house protection duty after all!

Yes the Navy Seals and the FBI had the HK MP-5 10mm guns, they ran several different ammo most being under the 1100 fps.  Much of what I saw being used in the 90's was Federal ammo but they was possibly some Winchester as well! 

At the range I frequented I recovered a bunch of their brass as shot from the MP-5's, many of these would have show case failures on the initial firing.  This could be attributed to fast burning powders and stiff brass, in addition to the fluted chambers they were fired from.  Most of these brass failures had splits running lengthwise.  Out of 1000 cases I had seen 60+ failed cases in the bunch.  Then with sizing some others would show their splits.

WOW this is awesome info fellas.

But you all at times can hurt a wallet. Because you got me thinking who might be able to work on this and thread it for me

Shadow,

Way back when, I was given 2 Maxwell House 3# coffee cans full of that same brass. I thought it was a great score at a time when 10mm brass was far less available than it is today.

I quickly put that brass aside as being too damaged for reloading. You are correct- split cases were a common thing in that brass, I also observed "torn" extraction grooves. After tumbling and sorting the brass I would end up with a failure/discard rate of as much as 8%, and my case loss after attempting to resize would push that to 11%- and this was once fired brass!

Too much trouble and uncertainty for me. I think that brass is boxed up in the garage somewhere, or it went to scrap... or it was traded off? Who cares- I haven't seen it in 20 years and I'm not looking for it now! BUT-

I wish I had those coffee cans. Those old metal coffee cans were great and even better if you still had the plastic lid.

That's an old load I saw two decades ago. I fired some in .40 S&W.

These boxes are in good shape so it makes me wonder of Winchester is manufacturing this load again.