|A few years ago while testing the patterns achieved thru back bored barrels, the thought occurred as to how much a barrel could be back bored and still maintain its velocity and patterning characteristics. We back bored a 12 gauge gun as large as it could safely be fired, which was approximately the same size as a 10 gauge gun. There seemed to be no loss of velocity and the gun patterned just fine. In the meantime, a lot of the new 3 ½ inch chambered 12 gauge guns came on the market with basically a 10 gauge barrel on them, so we knew that it was possible to push the limit farther, but it could not be safely achieved by back boring as there was just not enough metal left in the barrel to bore it any bigger.||
The only answer was to go in the other direction,
which was to find a way to fire a smaller gauge shell thru a larger
gauge gun in order to see what happened.
The best idea we came up with to accomplish this was to make a
chamber insert tube that would allow us to insert a smaller gauge shell
into the insert tube and them load the insert tube like a shell into the
chamber of a larger gauge gun.
|Chronograph tests proved otherwise. The shells were maintaining and sometimes even bettering the velocities we got from the same shells when shot thru a real 28 gauge gun. There was just no explanation as to what was happening. There was no way the 28 gauge wad could be sealing in the 12 gauge barrel and gases had to be blowing by. Based on everything we have been led to believe about shotgun ballistics, what was happening was supposed to be impossible. It worked, so we didn’t care what was supposed to happen.||
The biggest surprise was that the patterns from the
smaller gauge shells conformed to the 12 gauge choke constrictions. If
we put in a 12 gauge skeet choke and patterned at 20 yards, we got
essentially the same or better percentage of pellets within the 30 inch
circle as we did when firing the same shell thru a skeet choke in a real
28 gauge gun. As the distance increased, the tighter chokes performed
We knew since the 28 gauge inserts worked, it was a given that 20 gauge inserts had to work as well, so the next test was to make an insert for shooting a .410 shell thru a 12 gauge gun. This would be the real test, and to our astonishment, we got the same results. The patterns and velocities were the same as using a real .410 gun. The 20 gauge insert was next, and we were not surprised when it worked just as well.
The patterns were good and the velocity was just
what it was supposed to be, so the next step was to see how it performed
under actual field conditions. Off to the clays range we went to see if we
could break any targets. After what we already knew about the patterns
and velocity achieved in our tests, we were not nearly as surprised as
the puller and our other squad mates were when the targets broke with
authority. Even after seeing what was happening, their comments were
that it can’t work because there has to be blow by occurring around
the wad that should lose velocity and blow apart the patterns.
Although the chamber inserts broke targets, they needed testing on real birds. Tests in the dove field showed they could wipe those gray devils out of the sky just as good as a real gun of the same gauge. The same results were achieved on quail over pointing dogs.
A funny thing had happened thru all of our
testing. We had been trying to find out how big of a back bored barrel
could be used before velocity and pattern percentages were lost, and
what we discovered instead was a way to shoot smaller gauge shells thru
a larger gauge gun. We could literally turn one gun into four different
gauges of guns by merely inserting our chamber inserts into the chamber
of the gun while utilizing the same chokes.
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