Heres a quick find on loading data.
45gr Spitz 21.8 gr Reloader 7 3,375 fps 2.280" Fed 205M Alliant
Suggested starting load: 19.6 gr
Pressure: 53,200 PSI
Now bugger off. 
EDIT: BTW I was only saying it should be able to handle UP to 60k psi. Try reading the full post next time. Oh and I'm not saying it should be done, but I doubt it would knock you on your ass. You may fall because of the surprise, of perhaps because the rifle is exploding around you, but not from the recoil.
EDIT EDIT:
I found this out, its alittle more than I expected!
Max chamber pressure for 5.56mm NATO spec is 62,366 psi.
Max chamber pressure for .223 Remington SAAMI spec is 55,000 psi
http://www.ar15armory.com/forums/I-m-AR ... 50294.html
Really? you actualy think you load a live projectile to shoot this thing? wouldnt that just blow the golfball to little bits? you use blanks buddy. plz read.
-Felipe
