Sidearm Savant achievement will not unlock

Same issue with PC version. I've meet the requirements on both normal and hardcore mode. Still zero progress.

Just stumbled here for the same reason, having just now beaten it on hardest difficulty with strictly the pistol, and rpg at the end. Didn't unlock. I'm on Xbox series x. 

Same here. I'm on Series X and I am not able to unlock the achievement. I've too have beaten it twice, once on easy and once on hardcore- no luck either way. 

I have the same issue on PS5. I did the mission on normal and was only using the pistol, my knife and the rpg at the end. The trophy did not unlock for me either.

EDIT:
I got it fixed.

Got this tip from the top comment of this video: https://www.youtube.com/watch?v=2FLZ7FgzquQ

"If you finish the mission doing the challenge, just wait until the start of the next mission lets you move, and then leave to main menu. Then go back to the campaign missions, hit continue on this mission, and it will replay the last cutscene and give you the achievement. It just worked for me, and seemingly others as well."

I was playing the mission night raid using only knives and the rocket launcher at the very end of the mission you need to use to take down the helicopter. The mission took me an hour using just the knives. I finished the mission and got the achievement for completing the mission but not the challenge or the achievement sidearm savant. That is insane, and needs to be fixed asap.

this fix worked for me. thank you 

Not necessarily a fix, but a nice workaround. Thanks, in my case I managed to get the achievement.

doesn't seem to work for me on steam, this is getting ridiculous 

Thanks this worked for me.

+1 it worked reloading