In a word, no.
You are going to level up, opening new options. The MTAR is going to level up, opening new options.
The set up of your class and the gun will change as you move it to gold (you need every AR gold to get them diamond)
Use the gun. What are it's traits? Does it have a fast or slow rate of fire compared to the other ARs? Is the recoil mild or wild compared to other ARs? Are the iron sights good or bad compared to other AR's for both sighting targets and not obstructing your field of view outside the sights? How is the ammo supply? etc etc.
Once you know what a gun does (and more importantly what it does NOT do,) you can utilize available perks, attachments and other equipment to create a class with survivability while using that weapon (the MTAR).