hmm...
it's ok, not too good, not too bad. Maybe the barrels are too edgy (uhm... the whole gun is a bit too edgy) and you could add a lil' bit more details.
also why don't you upload the rendered image? you can save the rendered images! Go to "FILE => SAVE RENDERED IMAGE" Or just press "F3". usually it saves it as .jpg and you can define the save path seperately for every render image
Blender's a nice programme :3 I use it too (look at my art submissions, everything 3D has been made with blender! ^^)
