There was a time when I bashed the AR15 time every time I heard somebody rave about them, but that part of my outlook on the design has ended.    The differences between AR15 rifles as varying as the differences between cars.  You can get a compact car, pickup truck, van or monster truck and they all basically work the same on the outside, they roll, drive and turn, but internally they can be different and they all have different operating purposes.   The AR15 upper receivers you see now can be direct impingement, piston driven, 22 caliber converted, 6.8 SPC, 50 Beowulf, and on and on.  I can’t back it up, but I’ve read there are up to 40 different calibers you can get them in.   I really only could ever seen the need for 3 or 4 of them, but the design is so well received, that there is still plenty of new things to come for the design.

I have always been a fan of piston guns and not direct impingement.  Modern technology has made firearms more reliable even if they are still DI guns and arguments about gun reliability really only get blamed on the operator and not the designs.  If you want to compare an M16A1 to a piston driven gun it’ll be a slaughter over reliability, but AR15 really give you what you pay for them.   I am an LWRCI upper receivers fan.   If you still have an old Bushmaster DI gun laying around and wants something really different, you gotta spend the dough, but it’s fun with less cleaning time.  If I think of the last 20 times I went shooting, and did no more than 10 minutes of cleaning each time, I’ve saved hours of slopping gun cleaner around.  Gun cleaning supplies don’t cost much, but if you shoot often and clean your guns,  you will save time and money on just those things as well as bolt carrier life ect by switching to a n LWRCI upper receiver.