This is for his testing cycle (or break in if he likes to call it that) at the range...clean, shoot batch 1, clean, shoot batch 2, repeat. Iif he finds a round that works stick with it and shoot until the accuracy drops off...then clean. Since he doesn't say what firearm he's shooting nor do I know what barrel he's using I can't give him a number of rounds to clean between...it's up to him loss of accuracy is a good indicator on the bench NOW is the the time to clean.

As to how often I shoot- every day, number of rounds? Couple of hundred to thousands, cleaning periods vary based on system and what's going on and what we are testing.

I have a UMP with 3K+ rounds in it with no cleaning. I am running a Mod 0 test that has 20K+ rounds with no cleaning, I have a rifmire that I use to compete with and clean it nearly each time I come off the line. Today I've started playing with the Norell 10/22 conversion...I'll clean it when it begins to malfunction. My LRM 169 gets used almost every day...never really cleaned the barrel or the suppressor, I steam the lower and upper and oil it. When it really mattered, I cleaned my weapon every day, didn't matter if I fired it or not.
Unfortunately there is no magic answer for cleaning firearm and at what interval. In fact some firearms do better when they are not cleaned. I have suppressors that I have NEVER cleand and they have tens of thousands of rounds though them.

Again the question was about break in, not cleaning. My suggestion still stands, break in the rifle by shooting it and testing ammo in it. To keep as many things as equal as possible, clean between batches of ammo...after that whatever procedure you have for long term gun care and PM is between you and your gun.