Only at vet 3, they need to lose 2-3 model before that.
This is a game about unit preservation. The player has no input in this decision.
Guards started with 2 weapon and could only upgrade with 2 more so they did not actually have a choice. In addition they started dropping after losing 2 model from Vet 0.
I play the game I know how annoying losing weapon is, I also know that the most annoying weapon to lose is Shreck or Lmg34 especially to single explosion that wiped out your full health squad.
In the end of they if you find so annoying do not double equip your squads, it is an option you have...
I think the point that Hector is trying to make is that neither Tommies nor Guards have a choice about weapons. That's because both squads are being forcefully shoved a pair of rifles the player cannot opt out of. At least, for Guards, the PTRS rifles are, still, useful for something.
Tommy weapon dropping is also completely different from dropping weapons when getting wiped. Weapon upgrades can become randomly unavailable to the squad, already by the time the squad drops to 3 members. LMG gren squads can rely on the fact that the LMG will be available to them, as long as there is 1 model left alive. Thus, LMG Gren is a no-brainer. Bren Tommies has a trade-off.
This is a super frustrating mechanic that we want to get rid of. However, for the reasons outlined elsewhere, this would require a minor Tommy rework to keep balanced. Unfortunately, we are not allowed to make such a change for the time being.
I like Barton's proposal about forced weapon drop on wipe, as this would solve a lot of issues (especially Soviet infantry being unable to procure weapon upgrades of their own).