cant get a bolt and barrel to headspace?

[saltydecimator 482]

have a s12 that i couldnt get to run, so decided to sbs, then changed my plan, but hte current barrel im trying to mate with current bolt assy, wont headspace... whats the relationship of that hood on top of barrel to kicking the bolt into the lugs?  thanks!!!

[MLM0358 107]

The angled part of the hood times the rotation of the bolt into the front trunion. There is a lot of bad advice in the web  about filing the lugs to set headspace. I prefer to do it right and simply press out the barrel slightly, then press it back in again setting the headspace by proper barrel insertion into the trunion.  Press a little, check it, press again, check it, until it headpsaces.       Once it is headspaced, it's very possible that the barrel retaining pin may not quite not up with the groove in the new barrel.  Redrill it  using the trunion as a drill guide and use a metric coiled sporing pin from McMaster Carr. --  M4 x 35 is part Part # 91612A173  and this usually does the job.  You'll need to grind done one end just a bit to fit the width of the trunion.

[G O B 3,516]

NEVER FILE OR GRIND LUGS!!!!

If the bolt  and receiver are from a factory set, then they should be GTG;

If the bolt and receiver are a miss match, new or used - THEN the bolt needs to be LAPPED to the lugs. Lapping is done with very fine compound - you are only checking to see if BOTH (or all) of the lugs make full contact, so that they share the load evenly..No need to remove metal, just make sure that the parts do engage fully, and the bolt is sharing the load equally on the lugs.

 

Malcolm  nailed the head space procedure in the above post.     

[6500rpm 670]

First, is this the barrel and bolt that came with the receiver or a different barrel? In general, it's not a good idea to do anything but lightly lap bolts, even more so on an AK platform. Maybe Mike or someone more versed can chime in on oversized pins. Malcolm seems to be on the right track, if the pin channel has already been drilled (not a virgin barrel), it just depends on how far it's off and how big you need to go in the pin (usually there's an offset, but once again, I'm not sure how forgiving the S12 is in that respect).

[saltydecimator 482]

yep it was diff bolts/carriers with diff barrel.  once b/c would h.s., other wouldnt.  so i just went with the one that would.  i assume its that dang hood?  great explanation folks, im foggy on some stuff, hve to re-read but im feeding the baby and cant focus...