I got a bit excited when i got my hands on one of these but sadly it just doesnt make any sense.
Lets compare this session Xl stats to this session Ar stats.
Firstly the Ar has long range whilst the Xl has accurate, this means the ar will have a better to hit chance unless you have 4 pe or less.
statswise
Range:
Single: Ar:42 Xl:35
Burst: Ar:35 Xl:30
Dmg:
Ar: 14-23 both modes
Xl: Single 18-29, Burst 12-19
Weight:
Ar 3175
Xl 4082
Magazine size
Ar: 36
Xl: 20
Burst rounds
Ar: 12
Xl:8
St req both 5
The xl also costs roughly 3 times the ar.
Its pretty clear that the xl is worse everywhere except for the single shot damage but why would you use this over a .223 if thats what you were after.
How about either extend the magazine to 24 rounds or make the burst 10 rounds and make it deal its full 18-29 dmg in burst mode aswell as single.