Does it matter if you use the 10 rounder or 13 rounder on the 30 extension?

Have both 10 and 13 rounders and was wondering if I can use the 10 rounder on the 30 extension?

Thanks in advance

Honestly don't know. I haven't tried it, and I don't have any 10-rd magazines to look at, but the magazine body, floor plate, and follower are used for reassembly with the Mag-Ex. If any of those parts are the round limiting factor, then there would be issues. For what it's worth, the kit is now marketed as "25+" round extension, presumably due to changes in the spring resulting in a lower RELIABLE round count and feed.

The pre-ban magazines are also known to be problematic with the Mag-Ex kit. Solscud007 has posted some info on that too.

I have both. But never tried my 10 rd mag with extension.

The problem I see is that the 10 rd mag has vertical ribs on the inside of the mag body. I don't think the follower will traverse thru the double stack magex and into the single stack 10 rd mag easily.

Also why would you want to extend a 10 rd mag? Anyplace that requires a 10 rd mag probably makes it illegal to extend them.

My dealer had a bunch of 10 rounders that were given to him by other Kriss buyers. He gave me a few and I didn't want them to go to waste.

try it,
if it doesnt work take it apart and use it on a 13 rounder