Check for charging handle gap. Link to how to check. Bolt Gap - Cocking tube gap check for builders and buyers.
Clean it around the lugs in the trunnion. My c93 did have some over spray and grit. I also took off the bolt head off and cleaned out the crappy oil.
I use Tera Gun Lubricant and for me makes a difference.
Always use the HK slap to get it into battery.
It also has gotten smoother after a few trips to the range and cleanings.