Details
Most Ithaca imports have chrome lining in the barrels, a typical SKB treat.
One of the first detailed tests that I did with super-long forcing cones used an 1100 12 ga. skeet barrel and Win. AA 9's, 1-1/8 oz., with the same box of shells for the "before and after" shooting.
Target paper about 40 x 40 (roughly) shot at 25 yards
Before: 550 to 580 on the paper
After: 620 to 640 on the paper, and there is only about 660 in the shell.
Conclusion: open choke barrel that had about 10% of the total shot load that had previously been "flyers" was now hitting on the paper and the center section showed more uniformity. Where prior to cone lengthening, there were some center clusters with 2 and 3 almost touching in small groupings, afterward had more even central spread without the 2-n-3 mini-clusters.
Center spread that is more uniform and better filled pattern fringe (by the flyers being brought into the pattern) will make you more likely to get game or targets that you intend, and less likely to wound a bird outside of the pattern zone.
The lessened deformity of the pellets ensures straighter flight for patterns that are not tighter up close, but have less flyer spread out far. Numerous shooters have commented to me about their killing power at ranges beyond what they would have previously attempted, and this is with small gauges and fairly open chokes, to boot. Start your rounder, less deformed shot with a little more velocity, hold that velocity better, have less spread at longer ranges- now there is your recipe for improved effectiveness.
Picture 1 is of a standard forcing cone, and some rust from owner neglect is visible, along with less than perfect chamber wall texture. A small polish would eliminate the rust, add surface smoothness without altering the dimensions, and improve extraction reliability across a wider variety of shells. The forcing cone has less shadow at 3 o'clock than other areas, and proves that the chamber/forcing cone juncture is not centrally aligned to the bore of the barrel. One side of your shot column will be hit and squeezed harder than the other side. Pattern uniformity suffers because of this seldom-recognized fact.
Picture 2 is of a standard forcing cone lengthening, about the 1-1/2" amount typically done by most shops, and a small improvement according to tests done by Ralph Walker and others, about 30 years ago. Pronouncements from that era seem to be chiseled in stone, and inviolable, sacrosanct, and dare not be questioned in the soundness of the conclusions by any jonny-come-lately's, according to a few "keepers of the truth".
I just wonder that since Ralph admits trying only up to the 3" length, and with his era's modern shells (aka 30 year old technology), do we leave advancements for other areas of shooting alone at 30 year old results, also?
Picture 3 is of a super-long cone lengthening, with fine polish surface to match the interior of the Remington barrel, and picture 4 is of a slant view to show more of the surface to see that no roughness is present.
Which do you think lets the shot flow out of the crimp easier, and which has a more gentle squeeze to gradually fit the shot stack column to the bore? Less restriction is going to create less back pressure (chamber pressure) but still have more base wad surface to apply the pressure for some length of the acceleration zone.
That helps to explain the apparent increase in average muzzle velocity that I have chronographed testing before and after with the same shells and both barrels of a Browning B-SS 20 ga. The velocity variance between shots was sharply reduced as another benefit.
For the real nut, I have done 12 ga. forcing cones even longer than the super-long cone pictured.
see my previous posts for more insight from the gunsmith perspective.
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The Shotgun Shop, Arnold MO 636-282-4379
Specialty Gunsmithing, custom choke work, all gauges, thin barrels
