www.undergroundmodshop.com is where u can get the Apex adapter sleeve for $14.99. and as far as i know, it should work just fine on the stock a5 barrel. the apex without the tip i believe is just under 8" and the stock a5 barrel is 8.5" so it would probly be a lil better. also i believe the bore on the apex is a tiny bit larger so the stock barrel might be a little more pickier on paint then the apex. good luck.
chomelian out.