Q: About leveling weps

[RiftwalkSniper]

I'm curious as to what determines how much exp you get for a weapon you're leveling? Is it the AI's level? How much damage you do? How many people you kill?

Also, should I level and pick up new weapons as I progress through the game, or take a strong weapon and beat the story and planets, then worry about grinding and leveling weapons? I ask this because getting through the planets is very slow when I pick up a new weapon, for example my karak is level 24, but the damage is so poor against the enemies till it's almost 30 because I have no room to mod.

Thanks guys!

[Robm]

The amount of experience you get is based on enemy level and if you use that weapon to kill them, and go ahead and start grinding through all the weapons, don't be like and have to finish leveling everything up. 

[Cyborg-Rox]

You've probably already figured out that the numbers that pop up when you kill an enemy (besides the damage you do) is the Affinity, or XP, you get.

XP from enemies you kill is given to the gear you used to kill them with, but if someone else kills an enemy, that XP is shared to all your gear.

[NinjaZeku]

Enemy type (heavy / Eximus units FTW) and level affect Affinity gains.
[For leveling gear fast, shared Affinity from Squad members mass-kiling stuff is generally the fastest way.]

If you find a weapon you like, feel free to stick with it and at least use a Catalyst on it, there's always time to grind later :P
[Once you fall victim to that which shall not be named discover Draco, you'll be getting from 0 to 30 in one or two missions, heh.]

[PotatoTrapdoor]

The amount of affinity that enemies drop is based on level and type. For example, a level 40 Elite lancer may drop ~200 affinity, whereas a level 40 Bombard or Heavy Gunner may drop ~900 affinity.

Weapon and Warframe affinity use goes as such:
Warframes automatically receive 25% of affinity from weapon kills, and 75% of warframe kills. If you get a kill with a weapon with a warframe and 3 weapons equipped, then the Warframe will recieve 25% of the affinity dropped. The remaining 75% goes to the weapons. If one has 3 weapons, then each gets 25%. If one has 1 weapon, then that weapon will get all of the 75%.

[Airwolfen]

43 minutes ago, PotatoTrapdoor said:

The amount of affinity that enemies drop is based on level and type. For example, a level 40 Elite lancer may drop ~200 affinity, whereas a level 40 Bombard or Heavy Gunner may drop ~900 affinity.

Weapon and Warframe affinity use goes as such:
Warframes automatically receive 25% of affinity from weapon kills, and 75% of warframe kills. If you get a kill with a weapon with a warframe and 3 weapons equipped, then the Warframe will recieve 25% of the affinity dropped. The remaining 75% goes to the weapons. If one has 3 weapons, then each gets 25%. If one has 1 weapon, then that weapon will get all of the 75%.

Not exactly. While this is true for most affinity gains (including shared exp you receive) it does not go that way for kills that YOU make.

When you yourself  gain a kill with a warframe ability your warframe will gain the full 100% while a kill with your weapon splits it 50-50 between your warframe and the killing weapon.