Solely knowing one bullet penetrated 8" and another penetrated 6 inches, along with the description of the impact locations = a clear failure for these bullets to perform on this bull moose.
Three possible conclusions come to mind: 1) These 250gr bullets don't perform on moose. 2) These bullets aren't designed for use on moose, therefore if they don't perform, it's not their fault. 3) If the bullets fail to perform on moose, something else other than the bullet is responsible.
Take your pick:
Select #1 : this conclusion is equivalent to these 250gr bullets are not moose bullets since they're not designed to kill large animals like moose. Use this bullet on moose and you're asking for disappointment.
Select #1 & #3: this is equivalent to these 250gr bullets don't perform on moose unless used by a knowledgeable and skilled hunter that makes no errors in planning, judgement, and execution. They penetrate 8" or less on moose, however with the proper end-user knowledge and skill set, they're still a moose killing projectile. If you can't kill a moose with these bullets, it's your own fault.
Based on these two options, wise counsel for the majority of moose hunters is to use a bonded, lead core jacketed expanding bullet, or else a monolithic expanding bullet like the Barnes TSX. If you're specifically setting up for, and will
only take a long range shot at, a moose farther than 600 yds away, then a highly frangible lead core bullet like this 250gr Berger will certainly kill a moose with a broadside hit thru the lungs and ribs.
OR, a person could adopt the two-bullet hunting technique and have the best of both worlds at all times. Load/carry two styles of bullets for potential use on all of your hunting trips:
A) Select and carry a deep penetrating, controlled-expansion bullet for close shots which help ensure adequate penetration on huge tough animals like moose or brown bear. Bullets with high BC values, extreme accuracy, and wind bucking ability are not required for closer range encounters with these beasts. Carry these short range, camp/bear defense bullets in the magazine during all phases of your hunt. Very little time is required to develop these loads since they'll only be used out to ~ 300 yds. My load preparation time for camp loads is limited to simply shooting the bullets at 200yds to establish their POI. I don't really even shoot them for groups. Don't particularly care if they shoot 1/2 moa or 2 moa.
B) Select and carry cartridges loaded with the world's
ultimate most perfect long range big game hunting bullet available. One with a wind bucking and velocity/energy retaining high BC, tack driving accuracy, and certain expansion at long range low velocity impacts on large game. If you encounter the trophy of a lifetime at a truly long range distance, you'll almost certainly have time to remove the camp/bear defense loads from you firearm, replace them with your long range bullet cartridges, and engage the game at long range. How many times have you encountered a long range shot opportunity, and haven't had time to change out the cartridge in your rifle without the animal escaping?
Many hunters will avoid this approach as if there's some nasty penalty associated with it. Perhaps because there are no really large game animals where they hunt. It provides bullets well suited for both close and long range shots, and bullets best suited for big ugly snarling tooth, fang, and antler equipped man-eaters, or small plains game. A much better option than trying to make a single bullet perform well at both long range and short range. I've never felt handicapped in any way using this approach over the past 25 years of big game hunting in Alaska.
Why constrain yourself to a single bullet? There's no law limiting us to a single bullet for all applications. I like the controlled expansion, close range bullet for all close shots because it also provides the additional advantage of less bullet-damaged meat, regardless of the size of the game animal.