Originally Posted by JonM
counterboring is a common indicator of heavy use and can possibly indicate throat erosion up to the point of a dangerous condition. counterboring was a war time practice to bring old used barrels back into service to meet military need. it was a common practice in ussr, usa, and british militaries during ww2.
personally i pass on such rifles because if i decide to sell it later the value isnt there. its also a huge risk on whether the barrel is too far worn in the throat area.
some counter bores can still function just fine but buying one without checking the throat with a go-nogo-field gage set for that caliber is a big risk. i just dont bother with such milsurps unless its super cheap and i need the parts.
Trust me on this Jon: Collectors generally agree that the damage being repaired by counter-boring a rifle was caused by improper cleaning of the rifle with the steel cleaning rod. Not because the rifle is shot-out. The top inch or so was damaged, and once the damage is repaired, by counter-boring, the rifle is in good condition again.
On the M-38 rifles, all, or nearly all, of them were counter-bored as a routine
part of the refurbishment process. Apparently the Soviet armorers didn't feel that it degraded the quality of the rifles. From a shooting standpoint, it is far better to have a counter-bored rifle than one with damage to the crown.
If you are buying a Mosin-Nagant and hoping for a fine long-distance tack driver, you are barking up the wrong tree from the start. As far as a counter-bore discounting the value of a $150.00, obsolete military rifle, well, maybe it would only be worth $149.00 to some folks.
If someone is interested in truly collectible Mosin-Nagant rifles, then they won't be buying many
rifles off the racks of a big-box retailer, (The importers have already picked over them) and you aren't paying in the under $200.00 range. Even if you are buying a high-end collectible Mosin-Nagant, then a counter-bore would not be a deciding negative. It just doesn't matter that much to serious collectors.
While I agree with the checking of the head-space on all 75 year old plus rifles, I have not yet had a failure on a rifle that came straight from the distributor, and I have checked a lot
of them. Checking head-space is smart, and if you only plan to buy one, have a gunsmith check it for you. (it will cost you a lot less than buying the gauges)