it is the same problem you face with the 7.62x39 and given the proper design there are plenty of AR15s that operate satisfactorily. the 223 also has slightly tapered case and also has to wait til the magwell is clear before curving, it functions just fine, it's all in how you build the magazine and how you address problems as they come up
also your relatively priced parts aren't relative at all. the AK74 hasn't been cheaper than a 5.45 build it yourself kit since 2011, I know this because this was the time I started toying around with the idea of owning a 5.45. at that time the prices were about neck and neck, once 2012 rolled around then the AR started gaining ground as the supply of AK74s went down and the supply of ARs stayed the same.
finally, have you considered that since the OP already has 3 ARs and is considering building another that he is heavily invested in the AR platform and chose that platform for a reason?(or set of reasons).
all guns lost in a tragic smelting accident.
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