Let's say I started w/ a 545x39 Bulgy krink kit and bought a 223 barrel assembly from K-var. Would the 223 barrel fit my trunnion in the 545 kit? What else would I need to consider for a good conversion?

Thanks

If your lucky then the 5.45 trunnion has the same diameter as the barrel.  If not, then the barrel OD needs to be trimmed or the trunion reamed.  Next, you will need to get a .223 bullet guide from KVAR, removed the 5.45 bullet guide from the trunion and install the .223 bullet guide.  OR, contour the 5.45 bullet guide to feed .223.  Next, must get a .223 carrier b/c it has a milled cut to allow the carrier to pass by the .223 magazine feed lips without resistance (explained by Bob from KVAR here).  Next, .223 bolt.  And that should be it.  So to recap :

1.  .223 carrier from KVAR
2.  .223 bolt from KVAR
3.  .223 bullet guid from KVAR
4.  modify either KVAR .223 bbl or kit trunion

Thanks Nuge

You would have to get a new trunnion because the 5.45 models are not cut right for the 5.56 bullet feed ramp guide. The correct one is also the same one used for the 7.62, it is marked "24" on top, not "23".