Here it is in a nutshell . The carbon 15 had alot of problems when first introduced . From what i hear Bushmaster has fixed alot of the problems with cycling and other function related problems . Is this true? I cant say for sure . I have found that the carbon 15 is to light for accuracy at any distance . the lack of weight makes the AR hard to hold still on a target .Cold weather makes the carbon rifle function less then perfect.The barrels used on the carbon model ar not all that accurate.And in my oppinion they are overpriced. A great place to ask this question is over at AR15.com There are alot of people over there that have hours and hours in the field and at the range with this weapon. I personally dont recomend the carbon for a calling gun . You can build a lightweight upper And come in at 7 LBS with a scoped Gun. I have built a couple that were this weight when complete. Hope this helps , Jerry .