best way to break it in is to go shoot the thing and then shoot some more
both my M1 and M2 were and are being abused from day one
I bought 'em, took 'em out and shot 'em and then shot 'em some more (mainly with Federal ammo- 2 3/4" 3dram 1 1/8oz loads)
How many notches are on the new one?
1 notch = full
2 = improved modified
3 = modified
4 = improved cylinder
5 = skeet
no notches might be extra full and plus the chokes should also state what they are on the side