mboylan

556 and 223 are the same cartridge. The difference is pressure. You will find quite a large variation in 556/223 cases by manufacturer. 556 cases really do not have less case capacity than cases marked 223. On average 556 marked cases have a tiny bit more case capacity than the majority of 223 cases. Some 556 marked cartridges have out of spec necks because they can get away with it. Just trim to spec and work up your loads by starting in the middle and moving up. There is both 223 pressure and 556 pressure load data available.

Yeah 556 is 223 +P. I have seen lots of 556 LC brass with out of spec necks.

A Vanek connector will work. You will be happy with that too.

I have never been able to get a steel guide rod to run 100%. At least not ones for Wolff springs anyway. My G34 seems to like slightly flexible guide rods. It will run 13lb and 15lb ISMI springs just fine.

Yeah, it would have to compete open in USPSA. GSSF is much more strict than production. Even an aftermarket connector or recoil spring will throw you into open. This blaster would have to compete against comps and optical sights in GSSF as well as USPSA. IDPA ESP is out too. That magwell won't allow it to fit in the box. The brass slug is illegal. The oversize mag release might be illegal as well.

When using a captured stainless steel guide rod in a G34, is it still necessary to cut off 3 or 4 coils on a 13lb ISMI spring like you would for a full length guide rod?