That is a good question. I am interested in what others have to say. I understand that CA either restricts or doesn't allow bullets with lead cores (pity the muzzle loaders and black powder cartridge shooters).

I have stayed away from mono bullets for vintage nitro guns because I wasn't sure how they would (could) spike pressure. However, with grooves cut around the bullets, I have read that there isn't a high pressure spike.

For the same length, mono bullets are longer than conventional bullets so you might have to use a lighter weight bullet.