Volcano has said magma is Joye 510. So as long as the Magma is not a 510-T
tank model and you
buy a Joye brand mega xl battery, it should work fine. Obviously it won't fit in a PCC for standard size 510's though.
The Joye 510 mega xl manuals are great. I love them, good hit (they seem to hold their voltage plateau up a bit better), sealed threaded end. And for the normal size ones, I like Joye 510 manuals. Just make sure, if you have the Magma PCC - look in and make sure there is a notch cut out of the battery tobes to allow for a button. My PCC from NoSMokeVA.com does have the notch and Volcana now offers manuals too so hopefully their PCC has the notch cutouts.
(510-T chargers seem to fry 510 and Ego
batteries - probably communicates differently with the battery)