The Speer 458s ARE bonded just like the DC/GD.

The 300gr is listed as jacketed but it IS UniCor aka DeepCurl aka GoldDot aka bonded
http://www.speer-bullets.com/ballist...nd=0&firearm=1

Why choose a pistol bullet if they offer a rifle bullet that will perform better at SML speeds? The cupped base on the GD/DC pistol bullets might not work well in a sabot depending on how fast you shoot them. I blew a few cupped based 50cals in 54x50 sabots and just BH209.

It appears the 458 has a cupped base also and the jacket is .022 thick. Far right bullet