Quoted:
as  mentioned above, i have seen the surplus ammo prices in 5.45 ($135-$165/1080) and am considering building an m&a parts 16" CAR. i cannot reload .223 for that price!! couple questions:

how does the 5.45 work in the AR platform?

I am seeing similar performance with my 5.45 rig compared to my 5.56, grouping's at 50yrd and at 100yrds are very similar. Haven't shot my 5.45 past 100 yrds yet.

i have read some problems with c products mags(my preffered). has there been a cure for them or is there another reliable brand?

Out of the 6 CP mags I own I had 2 that would consistently give me FTF's, I think my worries have been put to rest with 87GN's modified followers. Look down the page for 87GN's thread.

corrosive ammo: worth the $35/case savings or too hard on a non chromed barrel?

The only ammo I have ran through mine is Silver Bear 60GR FMJ and Wolf FMJ, I just ordered a tin of 1080 rounds of milsurp. From what I hear if you follow the correct cleaning procedures after shooting corrosive ammo your barrel and rifle will be just fine

will a standard 5.56 lower work on a 5.45 upper?

Yep

overall thoughts about this combo.

I couldn't be happier with my 5.45 setup, it's already saved me a ton of $$ on ammo. Whenever I go plinking with friends I know this will be the rig I grab, hands down.

thanks all