Copper after lead and lead after copper

At some point in time I thought someone said you can shoot lead after copper but not copper after lead. Is there any truth to this?

I shot a match yesterday and had not cleaned or shot my 45 since Perry. I was shooting pretty good with the 22 and having some good vibes going into CF. Verified my first shot on call but scoping after 5 shots showed 2 - 7's low left ( I shoot left handed) touching each other? Otherwise X, 10 and a 9. Next 5 shots were similar and ended with a 89, which is not bad. This pattern continued and I scored 2 - 86's. I shot 5 - 7s and 7 - 8's during the slow fire stages of the match. I called nothing below a 9, the shots all felt good but scores did not indicate what I saw from my end.

If I was jerking the shots would have been low right like the 7 I pulled on the last rapid fire target. My slow fire scores have always been solid, so I am wondering if there is any truth to the copper after lead theory?

I use Zero and Nosler 185 gr. JHP and Zero 185 gr. LSWCHP with VV N310 powder and a Kart NM barrel.

Due to human error imo you cant blame the gun right off, if you shot a good shot after a bad one then that shows its more likely on the shooter. I have several friends that shoot long line fmj and short line lead, so in that you are shooting lead after fmj and fmj after lead in one match and yes the accuracy will degrade in a dirty gun. When their shots start going bad they tend to stay that way. They clean the gun after each 2700 and have no problems, these are 2600 shooters.

I can only relate my experiences. When I was at the top of my game, I would shoot Nosler 185 JHP for slow fire and Star 185 gr. swaged lead hp for the short line. I was using a Kart barrel. I didn't clean the gun between centerfire and .45. My first shots with the Nosler in the .45 slow fire match were often in the mid to high 90's, sometimes a 97. I never worried about the ammo or equipment.

I turn it upside down and brush it out after jacketed use just to prevent lead build up

regards