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I am wondering with what parts they are building the recent A4's with? Auto bolt carrier, cage coded parts and the like?
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By recent, I guess you mean the latest batch, which I think were produced in early to mid 2018. I purchased two AR15a4s, assuming you mean the actual 20 inch AR15A4 model and not other rifles which may have shared the same rollmark on the lower, in 2019. I purchased them several months apart, and from two completely unrelated dealers. Both of them claimed they just arrived at the shop, yet they had been produced at least a year earlier based on the stamps on accessory kits and/or the preservation bag and their serial numbers are fairly close.
Mine have CAR serial numbers, and drawing from memory, they have c marked carriers (very lightly struck), MPC marked bolts, C MP 1/7 5.56 NATO marked barrels. I'm pretty sure both also had C marked uppers, as opposed to cage code uppers, but I am not completely sure on that. They are in the back of the safe so it is kind of hard to verify at this time.