TL:DR The L-Star will do more damage than the Spitfire.
Based on the trailer provided by Respawn on the L-Star the damage looks to be considerable. The Gibraltar seems to go down in 7-10 shots, but it is hard to see because it cuts in the middle of the shots. It doesn't look like there were any shields breaking on him either. The Lifeline goes down in what looks like 4-6 shots also with no shield as well. Now at this point we don't know how much damage was done to these characters before hand, but I find it hard to believe that as a crate weapon LMG with 3 mags of 60 rounds that the L-Star will less damage than the Spitfire even if it does have a higher rate of fire and larger projectiles. Respawn determined it was crate worthy and gave it the limiting factor of overheating.
Damage Numbers:
I will use the Lifeline as an example because it was more clear.
If the Lifeline had 100 health and the number of shots that hit was 4 then the damage would have to be over 25 per pellet
If the Lifeline had 100 health and the number of shots that hit was 5 then the damage would have to be over 20 per pellet
and 6 hits means 17
If you slow it down it on Youtube to .25 times speed looks like the number of hits is 5. This would mean the damage could be anywhere between 20 and 24 damage.
If it is 24 prepare to down kids in purple armor with 9 bullets fairly easily with the large projectiles. Squad wipes galore.
If it is 20 it would do as much damage as the old Spitfire and down purple armor in 10.
In either case this thing has the potential to be a beast in the Canyon. Pick it up any time you can.
If you have any comments or speculations please share. I can't wait for S2!
For Reference: (I can't remember which post from Respawn had the mag size for the L-Star, but if I find it I will edit it in)
New Weapon: The L-STAR Arrives
This season we're introducing the L-STAR, a rare and powerful LMG. This weapon fires large, high-damage plasma projectiles at a fast cyclic rate. The L-STAR is joining the Mastiff and Kraber in airdrop packages, and quite frankly, it's a beast.
The L-STAR's unique projectiles are much larger than those fired by other weapons in Apex. Players need to lead targets more at range to compensate for the L-STAR's slower projectiles, but on the flip side, they don't have to aim quite as precisely to get good effect on target.
All this plasma-fueled power comes at a price: the L-STAR will overheat if players hold the trigger down too long. When the L-STAR overheats, its lens breaks and needs to be replaced, which takes some time. Expert players learn to feather the trigger with short/medium bursts, taking short breaks to let the weapon cool down.
The L-STAR only spawns in airdrops (like the Mastiff and the Kraber), and comes with a limited ammo supply that can't be refilled.
Source: https://www.reddit.com/r/apexlegends/comments/c29n8z/speculation_is_fun_lstar_time/