In that case if you specifically want to build up for the burrower strain missions, you should get the Democratic Detonation warbond as your first warbond (besides, 95% of the playerbase says it's the best one).

It has a grenade pistol with 6+1 shots, which is generally kinda weak (imo), but it can destroy holes/fabs/ships AND poke burrowers, as long as you can hit the ground without the grenade bouncing away.

If a secondary is not enough for you, it has a mini-rocket primary with heavy penetration and shrapnel, and an explosive crossbow with comparable damage but medium pen; the former hits hard (bugs and helldivers alike), the latter is one-handed and you can expect to survive when using it in CQC. Kind of.