According to the muzzleloading rules here in WA, the projectile has to be pure lead and at least nominal .50 caliber or at least 170 grains, which is essentially a .490 round ball that's normally shot in a .50 cal gun. Both the sabots and the conicals I use far outweigh the power of that size round ball, both for deer and elk. For elk, I've been using either the 370-grain T/C Maxi-ball or the 350-grain PR Bullet Ultimate 1 Keith Nose solids (both full bore conicals). For deer, I've been using the 235-grain PR Bullet QT40 saboted bullets with amazing accuracy. For elk next year, I'm hoping to find a really accurate load with either of the 330- and 360-grain .45 cal saboted bullets I got from PR Rifle. I got some of the Ultimate 1 "Plinkers" (just means solid instead of hollowpoint) in both the Extreme (semi-spitzer) and the Keith Nose designs. I've heard very many good reports on both styles for elk, and they're CHEAP ($14.95 for a 50 pack).
Both of my muzzleloaders that I have now are .50 cal, and I would buy a .45 cal if I were buying a new one tomorrow. As long as your projectile meets the requirements of the law, the gun is legal. That means a .45 cal gun shooting any conical or even a saboted bullet that weight at least 170 grains is legal. I think a good quality .45 cal gun shooting a full load of 777 powder pushing one of the PR Bullet .45 cal QT conicals in the 360-grain size would be some deadly elk medicine. I might try a .490 round ball for the little coastal blacktails, but most definitely not for elk.
I hunt deer and elk exclusively with muzzleloaders now, and I recommend an inline for your first muzzleloader... or your last one. The traditional style guns are fun to play with, but I really believe that an inline is a better hunting gun. I hunted with my CVA Eclipse inline last year and it performed great. I hunted elk with my T/C Hawken in early elk season this year, but have switched back to the Eclipse inline for late deer. The Eclipse just fits me perfectly and is balanced well (after my changes), where the Hawken was heavy, bulkier, and much harder to carry. I've customized the Eclipse a bit, as I tend to to with all of my guns, but it just shoots wonderfully for me. As has been said, the sights that come on the CVA inlines just suck, pure and simple. After a few trips back and forth with CVA trying to make them work for me, they sent me a set of the Winchester brand Durabright sights instead. Those are
very nice metallic sights, second only to the T/C click-adjustable sights. This year, I added a Williams receiver peep sight and I can honestly say I've never had a sighting system that good on a gun before.
I've tried all the powders out there and have settle on 777 powder in the FFg granulation for both of my .50 cal guns. Cleanshot and Clearshot were both too hard to ignite reliably and had questionable shelf life in humid environments (like we have in WA). Real BP and Pyrodex were too corrosive and I couldn't always get home to give my guns a thorough cleaning every night after shooting, not to mention Pyrodex sharing the other substitutes' trouble with igniting reliably. I'm not a big fan of pellets because I like to fine tune my loads, and I've been using speed loaders long enough that it wouln't really be any faster for me to use the pellets. It would sure be more expensive, though. I shoot year around to keep in practive and those pellets cost entirely too much. I wouldn't advise using the 777 powder in the FFFg granulation, even for a smaller bore like .45 cal. It just burns too hot. I usually use FFFg black powder (and substitute powders), but that FFFg 777 powder was destroying my sabots and conicals and giving terrible accuracy. Even a bore button under the conicals didn't help. I'm getting much better accuracy with the FFg 777 powder. Don't pay the $24 or more per pound that all the stores are charging for 777, though. Kesselring in Burlington has it for $16.95/lb and supposedly some store down south there close to Olympia has it for about the same price. I'm usually in Kesselrings at least once a month, though, so I just pick it up there.
The most important thing for a new muzzleloader shooter to do is go shoot with someone who's been doing it for a while. It's all so much easier to understand if you're actually seeing it instead of trying to learn from reading about it. If you (or anyone) want some more details on any of this stuff or just want to go shoot sometime, let me know. I usually shoot up at the Everett Sportsman Club range, where I'm a member, and would be happy to show you the ropes.
Jason