This is very much a support build for end-game content, as the primary focus is getting the marks spread around. The sidearm is the focus. The X-45 shoots fast and accurate, and even more so with the Accurate talent and accuracy mods. Swap to the MDR for damage when marks are up. The MDR sacrifices some damage for accuracy as well, as marks should be the primary focus for a Sentry in PvE content.
Also, I will often drop pulse for some CC skill like fire turret or flashbang, since a lot of people run pulse. In which case, I will remod to support station duration or something. The turret/flashbang then feeds the damage from the MDR b/c of the dmg buff on status effects.
I consider going strike back instead of combat medic, but good teammates use combat medic, and since this is PvE build, I SHOULD be able to rely on a decent healing station to recover health, or as a last resort drop my revive box for a quick burst heal or revive.
The thing I find really fun about this build is that with the M700 Carbon, I can drop marks on a target and start hitting REALLY hard despite not having marksman gloves. This is really fun when the marks jump b/c of 6pc bonus, and then I can one-shot elites.
I do also go with an SVD over the M700 at times, with the same basic mod configuration.