Handguns, no.
Handguns are used within spitting distances. Even when I start out shooting a clean handgun at 25 yards, I cannot hold hard enough to tell the difference between impacts from a clean bore and a dirty bore.
I put a Ed Brown solid bushing in my Series 80 Colt, took it to the range, and first shot out of an oiled bore hit dead center at 25 yards.
This was such a remarkable accident, considering no sight adjustments from the old bushing, and it was the first shot, that I took a picture. Subsequent shots were not nearly so well placed and I did not take any pictures of them.
One shot groups make for the best bragging.
For a rifle, you have to take into consideration the distance and how well worn your barrel, and did you clean all the carbon and copper fouling from the thing.
The last M1a barrel on my Super Match, it was rocking around 4500 rounds and I JB bore pasted the thing and used Sweets to remove all fouling.
Point of impact radically changed for the first five or so rounds, I was clicking big MOA until the thing settled down and shot to the old zero.
Installed a new 308 Kreiger barrel on one target bolt rifle. Not a lot of rounds through the thing. First couple of shots with a clean barrel at 600 yards were exactly where I finished an across the course match a week or two before.
So it all depends. Mostly depends on how well you know your firearm.