I'm looking to buy my first ar15. The thing is I don't currently own any other 223/5.56 rifles. I do however have two ak74's and a ton of 5.45x39. I'm strongly considering getting a s&w 5.45 upper to keep ammo commonality. I just can't see the point of buying 223/5.56 when its so similar to the 5.45 which I already have. So with all that said, is an ar15 in 5.45 something that you feel is reliable enough to be a primary rifle? If I go through with this and end up liking the AR better than the AK I would want to make it my primary rifle. Any input would be appreciated, thanks.