I bought the 250 rounds for this testing from Patreon funds before I was able to get in contact with Hornady. They are using their own brass from what we can tell. The brass is on average 56gr vs the 60gr FN. It holds about 12.8gr of water vs 12.0-12.2 that I got from the FN. There is some type of coating on the brass like FN uses. 5.4gr powder charge, and we are meeting the BOX state velocities. On the same day we are seeing 170 fps improvement over SS197SR.  Penetrations depths on the pistol and pdw barrels are above the FBI Min. It is not a bonded bullet, so keep that in mind.

The bad news 4 case neck separations. 3 in the MK57, which because of the RDB and nature of the BCG saved itself from exploding. However the AR57 upper I have does not have any OOB provisions, and the second round fed on top of the broken case neck, and subsequently KB! the gun. It held up very well and I have no injuries, but it's down for the count. AR57-Center is replacing the upper and they mentioned starting mid last year they have made changes to it's BCG to help prevent OOB firing.
We've had case neck separations in the FN brass before so this is NOT uncommon. We will need more rounds down range. One thing for sure the crimp on the bullet is VERY STRONG:



5.7x28mm, 40gr Vmax, Hornady Black (90001) by Buffman Range, on Flickr

Thanks for the report...

Forrest

By the way, Matt, kind of makes me hold my AR57 a little differently, if you catch my drift...

Forrest

Very exciting. Velocity boost is +200fps over SS197 from the 16" barrel, so really promising PS90 load.

Massive improvement!