Call me. What do you want to know, brother... I got you...
The Mod H was just the Mod 0, 5th Special Forces Group took out the 18" barrels and had 16" barrels installed by the unit (civilian contract BADASS) armorers. They had PRI shorten up that full-length top rail, about in half. Dropped the front sight gas block from PRI, went lo-pro gasblock under the carbon fiber handguard, because it was midlength gas. They wanted something precise, but a little more maneuverable than the 18"-barreled Mk12 Mod 0s. 5th Group is also who came up with the Mk12 Mod 0s in the first place.
SF runs Mod 0s and Mod Hs. SEALs and Rangers run Mod 1s.
"Mod H" means "Mod Holland." Named after MSG Steve Holland. Precision Reflex is the only company that built either of these two rifles for 5th SFG(A), outside of the unit armorers converting the in-inventory Mod 0s they already had, and this was before NSWC Crane approval (on the Mod 0s). So it you want one that's perfect, in build and design, get it from them, Precision Reflex. Or, have me build it for you. Or, I'll out the details and you can build the beast.
I have a Mod H 6.5 Grendel - it's the one gun I'd pick if the bus showed up out front and said ":You can only bring ONE rifle..."
Mk12 Mod 0:
Mk12 Mod H:
Precision Reflex website:
https://www.precisionreflex.com/
When you get here in the Fall, I'll bring out the Mk12 Mod 0, Mk12 Mod 1, Mk12 Mod H, and the Mk12 Mod 2. You can shoot them all.