It's possible to bind "+acc" command to a key in order to get an "Accuracy overlay" shown while holding that key.
Example /bind l "+acc" will make the table show when you will be holding the "l" key.
But the percentages shown for Nailgun are clearly wrong. You may fire a single shot at close range and then see a 600% accuracy for that weapon, which makes no sense. I mean, if one or more nails of a single shot hit, you should consider it 1 hit/1 shot; if no nails hit, you should consider 0 hit/1 shot.
Maybe the problem could be somehow related to the fact that a single Nailgun shot actually fires 15 nails, which reach the target at different times.
Considerations:
- Wondering whether "Accuracy" medal (which is single player deathmatch only, which is earned if you land more than 50% of shots) calculations are affected, too. Harder to test, I fear... By the way, considering Accuracy Overlay does not consider Gauntlet and Proximity Mines, I wonder whether Accuracy Medal considers them or not.
- Shotgun seems to do not have the same issue. Considering that's an hitscan (instant hit) weapon, I guess the code is quite different.
- While doing the testing, be aware that to update the stats shown there, you have to release and push the button again, as the table is not updated automatically. IDK if that's on purpose to be able to see the stats of a "static" moment instead of ever-changing values or to prevent excessive computational work... or just an overlook. Thinking about it, if the table would have been updated automatically, people would have been able to enable/disable the overlay by typing /+acc and /-acc in console, which may have been nice, although not really definitive anyway (just a simple vid_restart would have disabled it again).

It's possible to bind "+acc" command to a key in order to get an "Accuracy overlay" shown while holding that key.
Example /bind l "+acc" will make the table show when you will be holding the "l" key.
But the percentages shown for Nailgun are clearly wrong. You may fire a single shot at close range and then see a 600% accuracy for that weapon, which makes no sense. I mean, if one or more nails of a single shot hit, you should consider it 1 hit/1 shot; if no nails hit, you should consider 0 hit/1 shot.
Maybe the problem could be somehow related to the fact that a single Nailgun shot actually fires 15 nails, which reach the target at different times.
Considerations: