The rifle cames in its plastic hard case with the logo of the Italian importer A.T.P. only with one magazine. This is realized in gray anodized aluminium and the bottom plate is marked ".223 cal./5.56 mm. NHMTG S/42 HARTFORD, CT". On the side of the body another stamp warns Restricted Military Gov't Law Enforcement Export Use Only. It's the typical banana 30 rounds M16 magazine with its own green plastic follower that guarantees the mag to work properly. The appearance is deceiving: an aluminium insert fixed to the bottom of the green follower is limiting the capacity of the mag to only 10 rounds, the maximum allowed by the italian law. Personally I had no problem inserting in the K4B mag well Colt's AR15 20 rounds magazines, nor M16 30 rounds (reduced to 10 rounds...) magazines with black follower produced by Okay Industries. The M16 mags by Parsons or Adventureline, always with the black followers, can get in but they don't drop free. Maybe with magazines of the same manufacturers, but with the green followers, a clue that they've been produced with more stringent specifications, this problem will not occur. If you can find them, you can use also steel made magazines of the Beretta SC70/90. I didn't have the chance, but who tested it told me that they are e little bit tight in the mag well. Why all this attention for an accessory like the magazine? Because if your brand new K4B jams or you are using the wrong kind of ammunition (my rifle flawlessly cycled even with the minimum load for the N140) or the magazine doesn't allow a correct feed of the cartridge. Rarely you will find other causes to your problems. "
From this website: http://web.tiscali.it/no-redirect-tiscali/saarms/English/technology/rifles/Olympic_K4B.htm