The size and proportions look great. I don't know how BIS did their M16 - they seem to have gotten the right overall length, but the receiver is way too big.
Maybe your flash isn't tagged properly with the "zasleh" name. Does it only show in the shadow, or is the whole thing visible all the time?
Did you inlcude the CfgModels or section? I forget if that's the exact word, I'll post an extract from my SR47 cfg that was written for me by Skaven and NoRSu (each sent me a config, and helped me modify it). That's the section that fixes the flash problem.
First check in your shadow LOD if the flash is tagged properly.