But iirc, there was one way more, about a screen showing some statistics about that weapon. You know, what I mean?
You are probably thinking of the bootypedia page for that weapon which will show the ammo it uses. But if you haven't researched the weapon yet, this won't be available. Many of the weapons, especially lower tiers, you will still be able to use without researching. It's just that the weapon statistics aren't available until researched.
Edit:
--- Double post prevented ---How do you know if you're doing damage to shields? And what are the best weapons for getting through them?
To expand a bit on Legionof1's answer:
Unlike armor, shields will always take damage from hits unless it is a damage type that ignores or passes straight through shields. Shields resistance varies with damage type. Damage types which pass straight through the shield will not drain it and will hit the armor as if the unit had no shield. Most shields will regenerate each turn if not at full strength. Typically shown in bootypedia as a shield type which defines how well it protects (if any) against each damage type followed by full strength value/regenerate value. For example 150/50 will absorb 150 points damage assuming 100% resistance level before being drained and will regenerate 50 points each turn until fully recharged at 150. So long as shield resistance level isn't 0%, the shield will take damage from hits. This means that even low power weapons that couldn't penetrate a unit's armor but generate a lot of hits per firing may rapidly drain the unit's shields. Once the shield is down, you will not see the periodic shield flash animation.