Well MD is not to far off, I have taken one at 180 with a Hawken 54 caliber But it had a 35.5 inch barrel I was using 130 grains of 2F and a patch RB. This was one I built myself.
My rifle was made with the intention of using it at Friendship and had an extra notch in the open iron sight and had shot 17 inch sting measure groups at Friendship so I knew what it could do.
Beyond that distance a PRB not only drops very fast but has lost a lot of energy.
The main problem with setting up to shoot accurately at long distance with a lead bullet is the slow speed and rainbow trajectory so you need an exact distance and once you get very far out that means you must range find the animal with a laser range finder capable of the distance the wind can also play a big part in how far it is practical to shoot.
If you feel you must go with a big lead bullet a White rifle and a mid weight bullet say around 400grains is what I would suggest, also plan on many hours at the range and a sight that is capable of the range you wish to shoot, a heavy bullet will start slow and have a rainbow trajectory but will keep enough energy for a proper hit at long range.

see, had I said to go wit ha 54 and you'd be okay with 200 yard shots, the others would jump on me with the cryin :D I know doc white said 175 for 54cal patched ball is fine for big game, but you know how it goes. Accusations start

PRB's lose energy so fast that they are not what I would consider to be useful past 75 yards for a 54 cal for elk. I will say it out loud here, 175 yards or more with a PRB is in my opinion unethical.
I know guys have pushed the limit, and maybe took a desperate shot at an animal and it came through. That does not make it the right thing to do. I have seen elk limping around after being shot with a PRB. I have seen elk that were wounded and not retrieved. We had a late cow hunt that a lot of newbys would go get a off the rack gun buy some PRB's and head out.

I have asked you several times MD about your experience with killing elk. You have given statements from others. How many elk have you killed besides the young cow? I have no use for People that give recommendations with no real knowledge of the subject. I have killed 14 elk with bows Muzzleloaders and rifles. I have helped with the killing of at least 20 more elk. I have never lost one but I have had some tough times. You guys that are shooting that range with a PRB need to think about what your doing giving those kind of recommendations. Ron

A 9/16" hole or somewhere around there won't kill?

watch the hunting channel, you'll see 20 yard gut shots from the bow hunters and 100 yard gun shots with snazzy centerfires.

Giving someone load advice is one thing, telling them how to shoot is another. You can't hold that persons hand or guide the bullet to the animal, thats going to take skill on their part and no bullet of any kind or from any rifle will make up for a piss poor shot.

Not right away in all cases at all bullet energies

Which makes the point why I think you should err on the side of caution when selecting bullets and energy left when deciding to take a shot.

Jon, on the one elk you killed, if it had been a 350 class bull, would you have taken the shot at 180 yards with a round ball? If so, you are a braver man than I.

If it had been a 350 class bull he would have probably been standing in a puddle , shaking so much he couldn't shoot at all. ;):D

You would have found me passed out with the gun cocked and a lump in my pants :eek:

Muley, why did you delete your post, I didn't have time to answer your question.