i purchased a 20in stainless steel fluted sabre defense upper from pk firearms-
marked 223.
i stupidly fired 100rds of 5.56 -now she jams and wont cycle.
i think it is a headspace issue-
now i went back to firing 223 and after 20-30 rds she jams up again.
1. how do you use a chamber reamer to 5.56 specs
2.is there any hope?
appreciate the help again

Start simple (and cheap):

Jam means different things to different people. Can you clarify? Failure to feed? Failure to extract?
How many rounds of 223 did you fire before the 5.56?
What ammo were you using?
What type of mags are you using?
How well did you clean and lube the rifle?  

I had a lot of trouble with the first AR that I owned. It turned out that I wasn't lubing the bolt carrier correctly.

thanks again for your response
jam- as in feed properly then after round goes off-bolt is stuck inside
requires some effort to pull back
and sometimes it will fire a round but will not cycle enough to get the 2nd round in the chamber-
so it becomes like a bolt action
i fired 100 rds of cheap brown bear 223-no problems
then i fired xm193 a little hotter-then it started jamming
then tired my friends win 5.56 55 grain and still same problem-gun turns into bolt action
and sometimes locks the bolt forward.
this has happened 3 weekend in a row-
i use c-mag 10rd and stock bfi 10rd mags
i clean the gun and it will fire maybe 30 rds then jams all over again

if you pull the bolt carry assembly out and hold it bolt down can you easily jiggle the bolt with your finger like the bolt is really loose, or does it move but feels like it fits kind of snuggly?