O ring for aap01 (g17) mag

[Pewpewpetie]

Hi all, currently trying to fix this extended aap01 mag I bought, knew it was leaking but was only £5. The gas is leaking from the corners of the square plate , from the pics you can see the current o ring isn't sitting on the corners enough to create a seal. Does anybody have any idea what size o ring works best or is there a square alternative?

[strykerles]

have you tried lubing the oring before putting the mag back together?

 

I've used plumbers rubber o rings before as they are much easier to get than specific ones for a magazine., can be got from places like wickes, b&q etc