Re: I think I might need a more explosive bullet?
Dekor, those jacks get pretty big. I went to the 55g bullets to get more blow up. The Sierra 55g Regular Blitz is fantastic when loaded with n-133 or 135. With either powder, the accuracy load seems to be right at a max load. These powders can vary a little from lot to lot, so I hesitate to give you what my rifle likes. I did get best results using a Rem 7 1/2 primer or a BR-4 with IMI brass. I was getting close to 22/250 Velocities with my 25" bbl.
A jackrabbit should look like a handgrenade went off in him at close range, and should be just about cut in half at 200 yards with the 55g Blitz at a muzzle velocity of 3350. The 50g std blitz is unreal also with loaded to 3500 on jacks, but there is a lot more blow up effect with the 55's.
You had a question on the Hornady 55g SX, yes it is a great bullet, and I can not say that it is more or less explosve than the 55g Sierra Blitz. I got stuck on the Sierra Blitz due to the extreme accuracy. I won a Benchrest match with a 22 PPC shooting 50g Sierra Blitz with an agg of .189 at 100 yards only. The 50g Sierra blitz really makes a mess out of a coyote, but I still prefer the 55 blitz on coyotes and Jackrabbits.
If you are interested in shooting the poly tip bullets, I did a test for PMC Ammunition a few years back Shooting ground squirrels. Their ballistician loaded 250 each of the 50g Nosler ballistic tips, 50g blitz kings, and 50g Hornady V max. The PMC Pres and I shot 250 straight of each type before going to the next type of bullet. The hands down winner was the Sierra Blitz king, with the V-Max being fairly close, and the Nosler Ballistic tips being a distant third. We judged the bullets on how far up in the air the squirrel was lanuched, or sideways launches. The Sierra blitz king simply is in a class by itself.
I have never shot a jackrabbit with a blitz king bullet to give you a comparrison. Part of the fun is trying different types of bullets and seeing for yourself what you like.
I can not say enough good about the N-133 and 135 powders for the 223 using the 50 and 55g bullets. I have gotten the best velocity along with accuracy, with benchmark coming a close second but with 125-150fps less velocity.