Alpha Trooper Inconsistencies

I recently bought an Alpha Trooper for my brother's birthday (him agreeing with me that the AT is the best blaster in our war setting), and noticed several differences between ours.
-Range/Power: Mine has a consistent 11-12m range with good darts. However, my brother's has an inconsistent 10-15+m range. Occasionally a dart sails from one side of the house to the other.
-Accuracy: Mine has good accuracy for a CS blaster, though from what I've read, this is normal. However, my brother's has more inconsistent accuracy. I believe it's due to the power.
-Priming smoothness: My grip slides back and forth very smoothly, as if the grip has been greased. However, my bro's feels like it's scraping against something. However, given that mine is nearly a year old (got for christmas 2010) and my bro's is new, this is likely due to it being worn.

Has anyone else noticed any differences between stock AT's or is this just our pair? I know UT got a bad AT and a good AT, and posted the results/differences, but I haven't heard of it anywhere else.