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Old March 26, 2011, 02:39 PM   #3
kirbythegunsmith
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Join Date: February 15, 2007
Posts: 75
Choke and Bore error/ deformities pictured, Part 2, Kirbythegunsmith

Part 2

Being mindful that a barrel change was the first thought of the owner, the inspection of the old barrel vs. the barrel expected to replace the previous one ought to be a significant upgrade in some aspect, and in the initial choice, there was an already-attached variable choke. At least the cost of re-choking was already covered by another shooter.

One other downside to the swap was the fact that the previous gunsmithing school project nature of the beast was the inclusion of a reblue over a bead-blasted matte non-reflective refinish of the gun to go along with the short riot barrel length alteration. The replacement barrel was of conventional Winchester blue finish and would have been a mis-match to the rest of the gun finish. That might not matter for a knockabout field hunting gun, but it is a point, nonetheless.

I did spot those bore imperfections that are pictured in the previous post, but all by themselves, they might not cause rejection since some deformity reduction was a definite possibility if deemed necessary to put the barrel into service. Cutting the barrel to remove the deformities would have made the barrel less than 16".

A close examination of the Herter's choke in place showed that the collet fingers that are squeezed by the threaded collar used for adjustment had been bent or kinked from shot pounding over the years and would no longer spread to an open choke. With the collar removed, the diameter was around a Modified choke, with the internal length of the (now fixed or unadjusted, at present) tapering section under 7/16". Ever see a choke that short before? When the collar was tightened down, the constricting length was a whopping .8" to an XFULL diameter of choke.

See here that the unfettered diameter is 17.8 MM on the gauge.


Notice that the collet fingers have little remaining gap in the slits- especially close at the front edges.


I noticed that a subtle ring can be seen in the tapering area from this rear view of the choke interior. Can you spot the inner "belled" curve distortion?


Here is an interesting twist to view the internal bore distortion. I made a "negative" to make the whited areas of the distorted bore stand out in the dark reversion. Any doubts of the presence of such a condition should be rightly now laid to rest. The bright white flecks are actually dirt particles I left in the bore to verify that the pictured area was in proper focus, and dirt that looks so clearly shaped could not be pictured otherwise.


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The original barrel on that Model-12 was looking better as the candidate for repair, once the possible replacement barrel had been seen to contain many problems not spotted by the buyer- but it is not necessarily the new owner's fault to buy something represented as decent condition by a scurrilous seller.

The revised job was now to improve the original barrel and eliminate the negative issues present:

too-thin walls present at the muzzle area impossible to remove

bore scrapes present behind the installed choke tube hole

no provision for a sight bead


This series of problems could theoretically all be alleviated by a long choke insert that was precisely fitted to support the thin section at the front, while reaching beyond the scraped area behind, and by being permanently affixed in the barrel- a bead could be mounted completely through the supported barrel wall and new choke in place acting as a solid unit.

See that the interior view has a centered and closely fit appearance- not bad- considering the previous limitations in the area due to offset bore remnants due to bore side scrape variances.


The muzzle does still show the differential wall thickness, and that can't be corrected without removing the high side from the exterior.


There is more to be explained concerning this repair in the next installment.

Kirby
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