[Ultra Tech] Antimatter Rounds Seem Bad

[VariousRen]

I'm a player in an upcoming game set in a TL12 world. The set up is that we're time keepers, government agents who preserve the timeline through whatever means necessary. This gives us access to LC0, and generally sets the stage for us to do whatever we want. It's not intended to be a super serious campaign, but a chance for us to fire cool ultra tech guns at bad guys and take a break from our normal TL2 game.

In preparation for this, I've been putting together the equipment list for my android warrior. Antimatter rounds caught my eye, since at TL12 you can fit an antimatter warhead into a 10mm bullet (and fire a LOT of 10mm bullets if you want). The actual damage of an antimatter round seems really bad though. For the smallest round the damage is only 6dx4, compared to the 8d(5) you can get out of a HEMP warhead.

The radiation damage that these rounds cause also seems like a real problem. At 100 yards from the detonation point the smallest charge is giving you 3500 rads, which is solidly in terminal radiation sickness territory unless you have some PF from armour.

Am I missing something, or are antimatter warheads just not very good at blowing things up immediately compared to normal high explosives?