First Try

[ShadesbyTone]

hey guys. it's actually my first go at conceptual art so here's my first picture.

[vardoburrito]

Nice sketch PLC.

Next step would be to clean it up.
Use straight lines where it needs.
Brush up on your textures and rendering skills
and then do the multiple views. 3/4 included.

Blender is a free 3D modeling softie, it probably wouldn't hurt you to start looking into 3D for quick 3D blocking ins. CGsociety.org for a 3D/VFX forum.

[Tangleworm]

I agree with Dwardo. Also, though I admit I haven't bought it myself, I'd imagine El Coro's weapon concepting video would greatly help you.
As for the design itself, it looks cool, but there seem to be a lot of unnecessary parts. The light and dark parts underneath the reload chamber, as well as the black thing underneath and between the reload chamber and cooling vents both look unnecessary, and the former's angles look irregular (Though this is a rough sketch, so it's forgivable).
Speaking of that, the angular look of the ejection port area sort of fights with the perfectly squared-out look of the cooling vents, as does the curvy bit between the trigger and the stock does with the entire gun. For the angle on the top, I suggest either squaring that out (This might let you put a rack on it) or making the cooling vent follow the angle too (though in this case you'll have to make it less extreme, as it would cut into the barrel if you did that right now).

The gun as a whole is also very long. Picturing it in my head, a soldier with his arm on the trigger and his shoulder on the stock would have to extend his other arm almost completely to reach the pump. Shortening the area between essential parts would fix this easily, and you can eliminate the other unnecessary parts mentioned above in the same step.

[ShadesbyTone]

thanks guys!
yeah true, i should get rid of that stuff.
thanks for the advice, ill try again soon