| Shoot 'em Up!
(cont'd)
Here is the target array I put together
of the actual targets:
Note that I have marked the final
"settling" round on each of the three #1 groups to distinguish
it from the test rounds. Firing the last settling/fouling round on the
test target allowed me to reduce the number of targets used and trips down
range.
I believe the second question has been
effective answered as well. Does the reduction to near zero bullet
jump negatively impact functional reliability?
I have fired over 150 rounds through the
prototype barrel at a nominal bullet jump of less than 0.005"
without a single bullet jump related functional failure. In addition, I
fired an additional 150 rounds of ammunition (50 at 1.140"+) in rapid
fire from fully loaded magazines in an attempt to produce a functional
failure without none occurring.
I'd say the answer is "No.
Reducing bullet jump to near zero does not negatively impact functional
reliability."
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Safety Dance...
Question 3 was "Is the
prototype barrel safe to shoot at maximum recommended powder charges (VV
N340 6.0 gr.) and near-zero bullet jump?"
In short.... "Yes, it
is safe."
The last part of the this test
session consisted of firing a series of 10 shot groups with progressively
larger powder charges to determine if signs of unsafe pressure levels
would become apparent. I fired ten groups from the
prototype barrel beginning at 5.1 gr. of VV N340
and worked my way up in 0.1 gr. increments to a final group of rounds
loaded to the max recommended charge of 6.0 gr. I am happy to report that absolutely no signs of
excessive pressure levels or any other unsafe condition were observed. I
produced a spreadsheet of the tabulated group data here.
Note that while this lot of
ammunition was loaded to an OAL of 1.140" nominal, the casings were
not sorted for length. While bullet jump remains constant (long chamber,
short cases mean the bullet head spaces on the extractor), some reduction
in accuracy may have crept in due to the less consistent seating depth and
taper crimp tension. The groupings are still surprisingly consistent.
Check out the target array on the next page...
And
then?
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