Editor recommended because this is the officially named Prestige Attachment for M15 MOD 0. It is not labeled BEST. Tradeoffs are quoted from official launch copy.

M15 MOD 0
Fire ModsMFS 5.56 NATO FMJReach maximum Weapon Level and Prestige the weapon.
Subsonic 5.56 NATO rounds prevents firing signatures from appearing on mini-map and improves damage range and inflicted flinch at the expense of bullet velocity.
Attachments 1
- Fire ModsMFS 5.56 NATO FMJReach maximum Weapon Level and Prestige the weapon.
Subsonic 5.56 NATO rounds prevents firing signatures from appearing on mini-map and improves damage range and inflicted flinch at the expense of bullet velocity.
Alternatives
- Base weapon / no prestige attachmentKeep the base gunsmith path if you do not want the official prestige tradeoff quoted above.
Evidence basis: Source
For streamers: add this as an OBS Browser Source — stream widget
Recommended · bo7-m15-mod-0-prestige-launch