I'll be honest. I haven't checked.

Is this still needed with the Last Stand update?

There's a bug for the silence smg when the survivors shoot it in the dark, the muzzleflash floating above their heads.

No clue, but I'm fairly certain that 20Cat derived his/her manifest from Urik's and expanded upon it. Do you use a custom smg addon? If the gun's first person muzzle flash uses the pistol's, then it's possible that it could fix it.

Hell, why don't you just subscribe and see if it fixes it?

Does this also fix "20Cat's Particle Manifest - Simple Version"?
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2094209471

I still see weird muzzleflash fly off somewhere especially with smg