I am posting these pictures and explanations of problems related to aftermarket choke installations in order to inform shooters that may not have had the opportunity to see any of my previous material and articles that demonstrate the lack of consistency and skills prevalent in the gunsmithing trade. The errors in judgment and lack of precision in the jobs brought to my attention for remedy will undoubtedly raise the hackles of a number of shooters that see the evidence I present (perhaps even in their own shotguns). The multitude of limitations in aftermarket choke tooling were obvious to me in the first versions ever offered for sale, and realizing those conditions convinced me that I should never be involved in any way with such defect-prone installations. I will only install my custom chokes or do American pattern choke install/re-installs with a much more precise tolerance than the typical factory and prevailing aftermarket jobs offered to the public.
There were related details in a previous 2-part posting here:
A prominent clue to the excess thinning of the shotgun barrel wall by the mis-applied choke installation was the edge vulnerability to a minor bump such as wrench slippage. The remainder barrel metal wall thickness (at the thinnest point) was well below the obsolete standards first posited as the minimum wall recommendations used to generate sales of choke installation tooling. Those former standards have been revised over the years and at least are somewhat more realistic to lately reduce the statistically unsafe nature of the typical aftermarket choke tube installation. This pictured deformity is also visible in another picture in the previous thread from an alternate angle.
The choke removal section of the tooling that also bores out the choke tube hole has some side drag shown in these next two pictures. Notice that the scrapings shown are (designated in a previous posting with arrows in a front-on view) comparatively light in the first view vs. what is seen in the second view.
the step-down from the original bore to the altered section is quite prominent in this viewing angle. That is a considerable difference that highlights the typically-seen offset of the choke installation from the barrel bore centerline.
Even the threads inside one side of the barrel look shallow in the first picture section, and the cut-lines of the tap have deeper edges and consequently more reflective scatter in the right section of the composite picture. Realize that the threads may be in one centerline orientation, and the choke hole and shotgun bore may each have a different orientation. It is possible to have multiple and skewed centerlines, so now you may better understand why sometimes a barrel may not be accurate enough in the basics of alignment to even allow a choke tube to remain tight with conventional techniques (this is only one of several reasons that chokes fail to remain snug). It seems that many ideas abound of how to remedy the problem of chokes loosening, and some even post that they never saw or had the problem. Does that mean that another shooter with the problem has a personal failure- or a mechanical defect beyond their control or skills to discern?
The existing offset nature of the choke hole and partial bore eccentric cut made a straight choke installation even more of a challenge than usual. The picture of the results already posted in the earlier thread showed the centered alignment of the new choke that was also designed to reinforce the ultra-thin remainder section of the previous defective choke installation. That choke needed to extend beyond the scraped bore areas behind that old choke installation and include a fairly close fit to the bore and old choke hole to be filled. Some improvement of the support was generated by opening the internal diameter of the old choke hole through the thread section to allow a larger diameter section for the "filler" area of the new choke. The threads were cut to a truncated form that removed some height and created flats across the thread tops that would improve the contact area between the hole and filler. The picture shows the flat tops of the old threads to be prominent and capable of providing excellent contact surface and support.
One last point that required attention was the installation of a sight bead after the permanent choke installation was completed. The remainder wall thickness was insufficient for a through-hole bead installation in the original choke hole area. The factory original type bead (seen in a previous posting picture before being swapped) was too short for the barrel length or impact, so a taller flanged base bead was used to improve visibility and lower the impact to just a couple of inches high in the 50-60 foot range.
Be sure to see my website and previous postings for more articles and information unavailable elsewhere.