There's two main kinds of lead free ammo.
There are the standard solid copper/copper alloy bullets that have been around for years. You can usually get almost the same weight as a lead core for only a touch more length.
And there are the compressed metal powder frangibles for shooting steel and/or varmints. They are supposed to disintegrate in the first inch or so of flesh but some report them passing clean through a coyote.
There are a bunch of other lead free bullets but they are far less common. Things like steel or tungsten core in a copper jacket (not always of the armour piercing variety), solid brass, etc.
I've shot a bunch of the lead free frangibles through my .223 and they are about as accurate as cheap off the shelf normal stuff. The bullet weight was 35gr but shot about the same PoI as 55gr lead core at 100yds. I also shot some of the Remington lead free frangible rounds in .223 meant for shooting steel and they where 55gr bullets and where no more or less accurate than cheap factory ammo.
I've shot a few of the solid copper bullets (Barnes TTSX and Hornady GMX) and they are very accurate; almost match bullet accurate. They are only slightly lighter than lead core; the 180gr ones I shot through my .300WM where about the same size as 200gr lead core bullets but where as accurate as Hornady 208gr AMAX.