I have shot Elk in Colorado with a muzzleloader and witnessed others first hand. I would steer clear of the Hollow Pointed/Aero Tipped PowerBelts and any of the hollow pointed conicals such as the Buffalo Bullet and Hornady Great Plains. Elk have about 5x the bone and muscle mass of even large Whitetails, don't go after them with wimpy bullets. I have witnessed a PowerBelt failure first hand at 28 yards, and my testing shows the 385 gr Buffalo Bullet/Great Plains conicals with the hollow point/hollow base are actually worse. If you hit the shoulder knuckle on an elk, approximately the size of a baseball, it has about 5x the mass of a large Whitetails that is approximately the size of a golf ball.
Get yourself some solid lead bullets, such as the No Excuses, White Super Slugs or Power Punches. Bullshop also makes some excellent Conicals, but he only offers them from October through April, after he has earned his living for the year.
If you want to go with a more modern type conical, get the 300 gr THOR all copper Barnes based bullet, or the 350 gr Hornady FPB.
Colorado has finally removed the bullet length restriction of no longer than 2x the bore diameter, so any length bullet is now legal for Elk as long as it is the minimum weight of 170 grains and at least .50 caliber or larger.
Here is some good Elk medicine. L-R: 350 gr Hornady FPB, 430 gr White Super Slug, 440 gr White Power Punch, 460 gr No Excuses/460 gr NEx Bullshop (same bullet), and the 480 gr White Super Slug.
Put a wad like this Vegetable Fiber Gasket Wad between the powder and bullet, it will seal out the weather and give you better consistancy.
Groups like these are possible with BH209 powder. Groups shot with NEF Huntsman, .502" bore and .503" bullets.
X= Cold Clean Bore or fouling shot.
The 430 gr White Super Slug plowed through the shoulder knuckle of this 5x5 taking out the lungs and top of the heart. Don't try that with a wimpy bullet. If you look real close you can see the entrance wound, it only looks high due to the angle of the pic and the way the bull is laying.
Wimpy bullets.
430 gr White Super Slug, same used to take the above bull from same test media as above wimply bullets. Actual bullet was not recovered.
350 gr Hornady FPB, taken from the same test media as the above wimpy bullets.
Any questions?