I've been thinking about getting a seperat upper for my AR. to save some money in training. but the problem I'm running across is the cost of an upper + mags. the cheapest I've seen a spikes 22LR is over $600. and the cheapest 5.45 is an oly arm at midway for $545 I'm on a pretty tight budget, so I cant just drop the money, I gotta save up. I'm feeling a bit partial to the 5.45, its centerfire and the surplus ammo is priced better than current .223/5.56. but apparently some of it is corrosive. so If I go this route I have to be careful to not get corrosive ammo/ or clean the rifle right after shooting it. I've thought about the 22LR conversion kits, but I'd like to have the accuracy that comes with a dedicated upper. and then there is the fact that it is 22LR and not a centerfire. does anybody have any ideas and/or recommendations? Thanks.