First, for all who are following the first thread:
I posted the photo again at the bottom so that nobody would have to bounce back and forth to study it.
With the Colt-Browning tilting barrel system, the upper lugs engage with the slide vertically, but lock horizontally in opposition under high shearing forces. Due to the bullet's forward drag and the slide pulling the barrel backward at the same time...in normal operation...the slide is literally trying to tear the lugs off the barrel.
The cause of the damage was simply insufficient vertical engagement, coupled with a relatively soft barrel. Adding to it was the fact that the Norinco barrels typically have a bit of fore and aft play in the slide...not unlike endshake in a revolver cylinder...so when the gun fires, the slide gets a running start at the barrel lugs.
Early Norincos have been noted for poor barrel fit, and this was present in almost all of them. I've seen it in several examples to some degree, This one was just one of the more extreme, so...a picture being worth a thousand words...I snapped a picture for future reference.
Due to the Norinco slides being hard and tough, the slide was undamaged. I suspect that the Chinese used soft barrels on purpose. They knew that their barrel fit was less than optimum and barrels are cheaper than slides.
A side effect of barrel lug deformation is an increase in headspace by a like amount of the deformation. Norinco headspace is already generous...for lack of a better term...and the headspace with this particular barrel and slide was off the scale, and case head support went out the window. Bulged, "Guppy Belly" cases is was alerted the gun's owner that something was wrong, prompting him to field strip the pistol for a look.
The direct cause of the lack of vertical engagement was that the aggregate vertical dimensions placed the slide too far above the slidestop crosspin's centerline. In many of the less extreme cases, I was able to "work around" the problem by peening the frame rails down and removing material at the bottom of the ways, and draw filing a few thousandths off the bottoms of the slide rails. Sometimes, it provided full or near full vertical engagement and sometimes it didn't quite make it. Not ideal, but much better...worthy of a new barrel.
With this one, there was no working around it. Luckily, the owner returned it to the dealer who replaced it with a good one after contacting the distributor who gave the go ahead.
Norinco corrected the problem fairly early on, and the bad ones only show up occasionally these days, having been culled out.
Later, I'll do a tutorial on how to quickly determine if the one you're thinking of buying has this problem.
I posted the photo again at the bottom so that nobody would have to bounce back and forth to study it.
With the Colt-Browning tilting barrel system, the upper lugs engage with the slide vertically, but lock horizontally in opposition under high shearing forces. Due to the bullet's forward drag and the slide pulling the barrel backward at the same time...in normal operation...the slide is literally trying to tear the lugs off the barrel.
The cause of the damage was simply insufficient vertical engagement, coupled with a relatively soft barrel. Adding to it was the fact that the Norinco barrels typically have a bit of fore and aft play in the slide...not unlike endshake in a revolver cylinder...so when the gun fires, the slide gets a running start at the barrel lugs.
Early Norincos have been noted for poor barrel fit, and this was present in almost all of them. I've seen it in several examples to some degree, This one was just one of the more extreme, so...a picture being worth a thousand words...I snapped a picture for future reference.
Due to the Norinco slides being hard and tough, the slide was undamaged. I suspect that the Chinese used soft barrels on purpose. They knew that their barrel fit was less than optimum and barrels are cheaper than slides.
A side effect of barrel lug deformation is an increase in headspace by a like amount of the deformation. Norinco headspace is already generous...for lack of a better term...and the headspace with this particular barrel and slide was off the scale, and case head support went out the window. Bulged, "Guppy Belly" cases is was alerted the gun's owner that something was wrong, prompting him to field strip the pistol for a look.
The direct cause of the lack of vertical engagement was that the aggregate vertical dimensions placed the slide too far above the slidestop crosspin's centerline. In many of the less extreme cases, I was able to "work around" the problem by peening the frame rails down and removing material at the bottom of the ways, and draw filing a few thousandths off the bottoms of the slide rails. Sometimes, it provided full or near full vertical engagement and sometimes it didn't quite make it. Not ideal, but much better...worthy of a new barrel.
With this one, there was no working around it. Luckily, the owner returned it to the dealer who replaced it with a good one after contacting the distributor who gave the go ahead.
Norinco corrected the problem fairly early on, and the bad ones only show up occasionally these days, having been culled out.
Later, I'll do a tutorial on how to quickly determine if the one you're thinking of buying has this problem.
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