COAL to mag size rule of thumb?

[bugle20]

How much clearance do you need? 0.025, 0.50"
Is there a good rule of thumb that ensures cartridges will fit and cycle?

 

[badthirtyone]

I regularly run as little as .010" clearance in many of my magazines and have no issues with feeding. You may need to deburr or polish up to get that to work consistently, but again, that's my norm and experience no negativity.

 

[MagnumManiac]

Me too, I run a minimum of .010" clearance in the mag unless a bullet likes something shorter than this.
I have 1 rifle that likes 3.375" and another that likes 3.390" with the same bullet. Both rifles have 3.4" mag boxes.

Cheers.