Need a dimension for .25 magazine

No wanting to start a fire here, but I would imagine it’s not just a case of increasing the size of pellet holes in a smaller Calibre magazine.
Different calibre magazines have differing pellet radius’s to ensure that the centre of each pellet aligns with the centre of the breach, so just reaming out each pellet hole may still cause damaged pellets being loaded into the breach or it jamming. But i’m Sure you are onto that.
 
Okay, I'm trying to pose a simple question. Take a magazine from any manufacturer; Air Arms, BSA, Evanix, JKhan, Hatsan, etc... and as long as it is .25 cal, please measure the diameter of the hole for a pellet. My problem is that the only .25 repeater I have is a Theoben Rapid MKII and those magazines are notched pockets. Therefore I can't get a measurement. 

I just need a dimension to start sourcing a proper reamer. I will worry about fitment when I get to that point.
Thanks

Mark