Semiauto 375 H&H Runs! 458 Lott Barrel in the works

[45flaco]

Hey guys,
The 375 H&H AR has been updated with an adjustable gas block and heavier buffer, which has solved the stock breaking issue.
Fired a bunch since then, decided it's working satisfactorily, and now I'm planning a .458 Lott upper and barrel.
all that really needs swapped is the barrel, but I like the 375 enough that I'd rather keep it on it's own upper to swap back to occasionally.

Link to a video of the test rounds with new gas block and buffer below, it shot stupid smooth. Ammo used was a mix of exceptionally spicy handloads with the 200 grain sierra, and PPU 300 grain factory soft point. The 200 grain load has slightly more recoil, but was still quite manageable.

https://youtube.com/shorts/a1EAQJ26Ugs?feature=share

 

[45flaco]

And yes, I know it looks overgassed because it's ejecting shells forward.
But this thing has a ridiculous amount of dwell time, and a very heavy buffer for reliability reasons. That bolt needs to move faster than an AR-10 bolt, because it needs to travel further (by a little more than an inch). The force to unlock and initially extract is quite a bit heavier. I've added about 6 ounces to the reciprocating mass, and this is where the perfect reliability is.
One of the few things that I do wish I'd been able to do differently would be the use of a roller cam pin, and some sort of fancy coated bolt head to reduce friction.