[Reckless]

SRC lowers are usually taller on the top ridge then others (TM, G&P, Cyma, even G&G) ... not a big factor if your willing to to some filling or sanding


if your not comfortable sand/filling/fitting the upper to the lower of different brands (it's only a couple mm's total... but you will have to take some off the upper and off the lower... and possibly if it's a metal G&G upper you'll have to shave the tabs at the back that grab the lower. ) .. then it's a good idea to wait till you can grab a whole receiver set .. or just a g&g lower to match your existing upper

I've been doing alot of G&P receiver set/peices matching the past year .. and it can be really frustrating .. LOL