I looking at a model 15-6 with a 6in barrel.It has a trigger referred to as DAO only 3lb trigger pull,does this mean i cant pull the trigger back and shorten the stroke? I have a model 15-4 that has a shorter barrel & different front & rear site with a much heavier trigger pull. Did this gun come from the factory like that or has someone altered it? The price is $475 is this a good price for a off roster gun in west LA? Thanks for looking