I need either gel blocks or a bunch of water jugs

so I can try this stuff out.  It's a new- to me at least- .300 Blackout subsonic ammo from Federal.  1000fps is claimed, and it's an expanding 190-grain bullet.

I had a chance to fire three rounds today; definitely subsonic, and at 30 yards three holes touching.  No, I didn't have the chronograph to check velocity, and that's all I had the chance to try today.  And, so far, have not been able to find any tests on the stuff to see how much it expands and down to what velocity.  Bloody YouTube won't load right now, I'll do some more searching later.

Things to find out...