[mhb]

The remaining energy...

of the 55 gr. FMJ at 600 yards is not sufficient to insure a clean or humane kill on deer-sized animals - in fact, I wouldn't even shoot at a coyote with that ammunition at that range.
Will it inflict a lethal wound? Maybe, if you are lucky enough to strike an artery or the heart, a major organ or the spinal column. But the chances of inflicting a wound that did not kill, or allowed the animal to flee and die unrecovered sometime later are too great.
In my experience, M193 ball ammunition is not accurate enough to insure hits on deer sized game at uncertain long ranges, and precise shot placement would be a matter of pure luck at 600 yards.
There are legal ramifications, too: most states don't permit the use of FMJ ammunition on game animals, many states have minimum caliber and/or muzzle energy requirements, and few permit the use of any .22 caliber centerfires for deer.
Then, there is the question of sportsmanship: I don't believe in sniping at game animals. It isn't sport and it sure isn't sportsmanlike.
The 5.56mm/.223 is not a deer cartridge with any bullet, really. Can it kill deer? Yes, under certain conditions. Outside of survival situations, I can't think of any reason to do so, or to use FMJ ammo for the purpose, and most certainly not at extended ranges.

mhb - Mike

Does anyone know how effective the 5.56 round is at 600yds for takedown power? I was watching some "Hog Hunting" on YouTube yesterday and wondered what effect the distance would have versus the game you were hunting. I'm not suggesting shooting rabbits or prairie dogs at this distance. Would it still easily take down a deer?

 

[mhb]

That puts a different complexion on the nature of your query.

The extreme range of all three of these rounds is far greater than 1500 yards. Any of them will inflict a dangerous and potentially fatal wound at ranges well beyond a mile. The extreme range of M193 ball is around 3500 yrds, IIRC, and it does not fall like the gentle rain even at the end of its travel.
A mis-directed shot at high elevation is the greatest risk, but ricochets can travel surprising distances with dangerous remaining velocity. More powerful rounds extend the extreme range potential significantly, and 172 grain or heavier boattail match bullets in the .308 and .30-06 class rounds can reach ranges around 5000 yards or greater.
You absolutely MUST be aware of everything and everyone possibly at risk when firing without a positive backstop.
You can't call a bullet back.

PRD1 - mhb - Mike

Thanks for the info (both of you). Here's a pic of our setup taken from 100yds. So far we have been able to stretch it back to a little over 200yds.

View attachment 41426

Pictured is a DPMS, LE6920, WIN 30-30 and a Russian nagant 7.62. Change the coyote to a family pet and a deer to maybe a child out in the field and this is why I asked about takedown power. When we set up we made sure that there was nothing in the background and no one shoots alone. We don't have the luxury of shooting in a heavily wooded area with massive backstops. There is nothing behind our backstop for almost 1500yds.