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SG43 Goryunov Headspace/ Reweld Questions

6K views 6 replies 5 participants last post by  Panzerfuhrer 
#1 ·
Does anyone here know the proper distance between the bolt and locking surface of the receiver AFTER the receiver has been welded back together? I'm tempted to build this thing like an AK by using headspace guages and calling it good when the bolt locks up nicely on "GO" but the only info I can seem to find on the subject is to take an unfired case, put it in the chamber, let the bolt go fully into battery, and once you're able to fit a .030" feeler guage between the bolt and receiver locking surface you'll be in good headspace.

Are these guys crazy or does this gun really need .030" of space for the case to expand before the rear of the bolt makes contact with the locking surface in the receiver?
 
#4 ·
With a unfired steel case in the chamber, and the bolt fully in battery, the bolt can be moved back against the lock between .002-.004"+/-This is measured at the boltface in relation to the breechface. The locking surface at the rear of the bolt is angled, as is the mating surface in the reciever. If you build the receiver too short you can relieve the locking edge of the bolt.
This was checked on a C+R, 1943 dated Russian SG43 in excellent condition. Not sure where the spec of .030" gap at the locking edge comes from but that is way too much, in my opinion.
Without knowing the state of the cuts in your kit, I tell you My technique. Having built a few of these guns as PS guns, with the front end of the receiver tack welded, a barrel installed, the bolt/oprod installed in the rear section with the lockup, an unfired case in the chamber, move the bolt into battery allowing the bolt to move into lockup in the rear section. It helps to remove the extractor and firing pin from the bolt so that they doesn't push it backwards while in battery. Stabilize everything so you can rap the rear section back and forth and assess the dimension that allows a bit of play of the bolt at the breechface. Allow for contraction, actually quite a bit with these guns due to the thickness of the metal, when tacking and final welding. It is better to be a bit short than too long, in my opinion, although in either case adjustment is actually very easy, just different means to do it. FWIW
 
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