Most used alloy for 223 bullets

You never heard of it because it wasn't too many years ago that a certain group of shooters got into a cast high velocity contest.  You have to have a high Antimony  content, which Linotype has, and you have to really push the velocity. With low pressure and velocity loads you're not goint to see it as much as the high velocity loads. I'm talking when I say high velocity cast loads equalling jacketed. It's not the burn temperature. It's a combination of the temperature on the throat, the abrasiveness of both the partially and the unburned powder kernels. in addition to the high Antimony contest of Linotype.  Do you know that I've seen a stainless barrel in 264 Win Mag that the bore was firecracked like a dried up river bed from shooting massive loads of 872 suplus powder which burnds extremely hot? Wouldn't you think that condition would set up a scenario of the abrasiveness of the unburned powder and friction wear from the jacketed bullet to easily start destroying a throat? The barrel manufacturer asked me how could that barrel gotten that hot. I said a few of those surplus powders burn extremely hot way above canister ball powders. I've done a test with that surplus powder where I loaded five 6.5 Jap rounds with a load of 4350 powder. The rifle had a fairly thin barrel.  The rifle was at 65 degrees F as it set in my basement shop.  I fired those as fast as I could cycle the rifle. After that the barrel was only warm and you could put your cheek on it.  I took the rifle back into the shop and let it set for hours to get back to the room temperature of 65 degrees F.  This time I loaded the rounds with 872 surplus. Shot those as fast as I could cycle the action. This time the barrel wasn't warm, it was hot enough to burn your fingers. I don't mean burn as in a 1st, 2nd, or 3rd degree burn, but hot enough you weren't even going to keep your fingers on there more then a 1/2 a second. That was a dramatic change in temperature between that surplus and stick powder. Imagine a 264 Win Mag is very overbore and has a large powder capacity and in addition to the powder burn heat you have frictional heat from the bullet going down the bore. 

With normal alloy cast load, and especially lower velocity ones, the most wear you ever see on your bore is a good polishing. I would imagine over a period of years of lots of low or normal velocity Linotype loads that there would be more throat wear then what you would get from regular lead alloys.