The Firing Line Forums - View Single Post - Does anyone know the caliber for colt SP1 Uppers?

5.56RifleGuy · May 9, 2010, 04:17 PM

Alright thanks, the lower is an a3 lower marked 223 but i couldnt find anything on the upper. I figure since the chamber is all in the upper, that is what matters. I use 55 grain 223 and it shoots great out of the 1 in 12 barrel.

So really, what is the difference between shooting 556 vs 223? I have heard 556 has higher pressure, but does that mean faster round or something?

thanks
Devin

May 9, 2010, 04:17 PM	#3
5.56RifleGuy Senior Member Join Date: May 9, 2010 Location: USA Posts: 1,212	Alright thanks, the lower is an a3 lower marked 223 but i couldnt find anything on the upper. I figure since the chamber is all in the upper, that is what matters. I use 55 grain 223 and it shoots great out of the 1 in 12 barrel. So really, what is the difference between shooting 556 vs 223? I have heard 556 has higher pressure, but does that mean faster round or something? thanks Devin