| Achieving
Near-Zero Bullet Jump:
The only feasible way to reduce
bullet-jump in the Glock is to replace the barrel with one where the
free-bore (lead) specification is reduced. Enter Kevin Mcintire of KKM
Precision. As I already had a KKM barrel for the Glock 22 (40
S&W), it made sense to use this barrel as the base from which to
construct a custom barrel. After much agonizing over the final
specifications and getting the custom chamber reamer constructed
($140.22), Kevin was kind enough to make a custom prototype barrel
($180.00) for me.
The only difference between the stock KKM
barrel that I already had and the prototype is the free-bore dimension.
This allows a direct comparison of the two barrels to determine if that
single variable makes a discernable difference in accuracy.
Upon receipt of the prototype barrel, I
set up and executed a quick preliminary test to see if any accuracy
gains would be readily apparent before incurring any further expenses in
the project. The test was conducted at my local range, Lemoore
Sportsman's Club, Lemoore, CA.
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I fired three series of groups in each
barrel (5 groups, 5 rounds per group in each series). Each series
employed a progressively longer OAL and thus a progressively smaller
bullet jump. All rounds were fired by hand using a simple wooden pistol
rest. Additionally, I fired a "fourth series" to test
functional reliability, essentially burning off large numbers of
multiple types of ammunition trying to induce a functional failure. No
such misfortune occurred.
The preliminary
test results were enough to convince me that a further
investment of time, money, and effort was indeed warranted to clearly
prove or disprove the theory. They indicated that:
1) You can indeed significantly increase
accuracy by reducing bullet jump to near zero, and
2) You can reduce bullet jump to near
zero without adversely impacting functional reliability.
So I moved forward with plans to conduct
formal testing. I solicited suggestions on drafting the testing protocol
from the forum members over at Glock
Talk. I received a number of helpful suggestions online
and by email.
And
then?
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