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Interesting video. Unfortunately, it only addresses fixing the symptoms but not the root cause. It is unlikely the bolt left the factory with a crater around the firing pin hole, hence something must have caused the rim around the hole to crater.
Cratering is not uncommon in semi-autos with floating firing pins having tapered tips. In this respect the SKS is no different than the German G43. Nothing stops the forward movement of the firing pin (especially when dry firing) other than the fact that the firing pin hole is smaller than the thickest part of the tapered tip. If the bolt face is thin or the metal is soft, over time the firing pin will act like a tapered punch and push metal outwards, thereby creating the crater rim.
In this cutaway of an SKS bolt you can see the taper.
From a longevity standpoint, the taper angle of the bolt and the firing pin should be identical. Then the firing pin tip and the tapered hole in the bolt have total surface contact and no deformation of the bolt face will occur. Unfortunately, this will not work as the firing pin will get stuck inside the tapered bolt hole the same way a tapered milling bit is held firmly in an identically tapered spindle. Slam fire will be the result.
Therefore the firing pin needs to be angled just a tad more pointed than the bolt. Then the only contact will happen right around the firing pin hole. If the firing pin is too pointed, it will start displacing the metal around the hole outwards, a.k.a. cratering. Aftermarket pins with wrong angles will accelerate growth of the crater rim.
A better design solution would have been to put a thick collar at the back end of the firing pin which limits the forward movement of the pin.Every record has been destroyed or falsified, every book has been rewritten, every picture has been repainted, every statue and street and building has been renamed, every date has been altered. And that process is continuing day by day and minute by minute. History has stopped. Nothing exists except an endless present in which the Party is always right. -1984 -
I posted this in OP's other SKS thread http://www.calguns.net/calgunforum/s...3&postcount=38 there is a thread from sksboards embeded in this post that is very informative on the cause/effect of popped or pierced primers and a cure...
Murray's Gunsmithing does offer a boltface stoning service very simular the youtube video that OP posted...
I sent a Yugo M59 barreled receiver to Murray for the neck and throat ream service because it was popping primers. The boltface looks good so I did not see a need have the boltface worked on. I will report back when I get the the rifle put back together and fire it...NRA Member
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