For sure, the mono bullets work well. It's tough for anything to live when a supersonic piece of metal is driven through its lungs!For what is worth, I've had amazing luck with hammer hunter 180 gr mono's in 30 cal. On elk. Over the years I've migrated away from the good old partition. This is mostly due to me moving from a thick forest (225 yard max shot distance, most under 100 yards) to very open country. I still run the partition in my 30-06 but I don't hunt with it much at all any more. I had a learning period about 10 years ago with my 6.5 SAUM trying many different bullets. For me, with my experiences, the ELD-X and the hammer hunters were the only bullets i found similar wound signatures to what i was used to with the partition. Now days I hunt smaller game like deer and antelope with the 6.5 SAUM and 143 ELD-X and elk and black bear with the 180 hammer hunter, and moose with the 300gr burger .338 (but I hate that bullet, it throws lead all over the meat. I need to find a new bullet for the 338). I do not have experience with the 1:3 class twist rate of the 8.6 BO, but i do like the idea of it. I will probably never build one since where I live now is such open country though.
The partitions have always been great, because you get the penetration and expansion of the base paired with the added wound cavity caused by the front of the bullet upsetting and breaking off.
I have yet to use the ELD bullets but they look to be one of the best choices today. I would absolutely choose them over a mono for any situation that doesn't legally require me to use a lead-free bullet.
And yes, 300 grains of 338 is a lot of lead to displace through a body. The 8.6 is an intriguing cartridge, and if going with a mono, the bigger diameter the better. Probably not the best round for open country, but would certainly solve the matter of excess metal in a moose, and a big subsonic with a silencer would be sweet in heavy timber. I just personally don't see 338 as necessary for a moose, and refuse to pay $4-$5 a round for my general purpose rifle when when the factory ammo I shoot is $1.50.