Download
the .32acp
spreadsheet (right click, select save as)
Download
the 9mm
spreadsheet (right click, select save as)
Comments from Bill: [comments are for .32acp, but apply
in general to other calibers]
That evil engineer in my soul
constructed a spreadsheet to play with the numbers.
It's an Excel spreadsheet, uncompressed and MIME
encoded. It should work correctly if opened from
within any recent version of Excel.
A few thousand words of explanation
may help.
Each row contains data and calculated
values for one cartridge.
Columns contain, left to right:
- manufacturer name
- bullet type (jhp, fmj, pf)
- caliber (all .32 of course)
- index: a value representing how well the cartridge
meets the criteria established by the weighting
factors. The values are relative and have no inherent
pgysical significance. Higher is better. See below
for formula.
- length: cartridge length (measured data) in inches
- wt: bullet weight (measured data) in grains
- vel: velocity (measured data) in fps - e/v: a
number, proportional to the momentum of the bullet,
derived by dividing energy by velocity. [Energy is
proportional to the square of velocity, momentum is
proportional to velocity.] - energy: energy in ft-lbs
(test result, calculated from measured data)
- fudge: a multiplier (fudge factor) applied to the
diameter ("expan") to account for
non-circularity of the expanded bullet. Used only to
account for the Glaser "bullet" being
multiple pellets. The current value of 0.5 for Glaser
is a vicious WAG. An engineered WAG would involve
calculating the combined cross sectional area of all
pellets not entering an exisying wound.
- expan: bullet expanded diameter (measured data) in
inches
- f*e: fundged bullet diameter
- penetr: average penetration (measured data) in
inches
The index of suitability is
calculated by adding five factors, with the relative
weighting of each factor in the total being
represented by user entered percentages. It is
intended that the user entries add to 100%, but this
is not an enforced restriction. To aid in keeping the
total correct, it is calculated and displayed (lower
left, cell B22) dynamically. The five factors are as
follows:
- length: relative length of a cartridge as a
percentage of the range from minimum to maximum of
all samples. This is included since there is some
indication that longer cartridges may be less
susceptible to rim lock.
- "mom": relative momentum (mass times
velocity) of the cartridge as a percentage of the
range from minimum to maximum of all samples.
- energy: relative energy (one-half mass times
velocity squared) of the cartridge as a percentage of
the range from minimum to maximum of all samples.
- wound: relative wound (cylindrical) volume of the
cartridge as a percentage of the range from minimum
(based on min penetr and min expan of all samples) to
maximum (based on max penetr and max expan)of all
samples. Lots of assumptions are attached to the
"cylindrical" part.
- depth: relative wound channel length (penetr) as a
percentage of the range from minimum to maximum of
all samples. In each case, higher is better.
The five factors are combined into
the index as follows:
index = length * length % +
mom * mom% +
energy * energy % +
wound * wound % +
depth * depth %
The five percentage factors you specify in the five
boxes a the bottom of the spreadsheet.
All values which you can change are
in red and include only
the five weighting percentages and a fudge factor for
each cartridge.
Four of the weighting factors are
shown in pairs: mom/energy and wound/depth. The two
members of a pair are commonly thought to represent
the same physical type of characteristic -- i.e.,
some folks like energy as a measure of how
"hot" a load is, while others prefer
momentum. So as not to take sides, both are
represented. Zero the weighting factors for those you
don't like.
Example: Say I think that wound
volume and energy should be equally weighted in
determining the best cartridge. Length is of no
importance to me, and I think that using momentum as
a measure of strength is nonsense. I enter the 5
weighting factors as:
length % = 0%
mom% = 0%
energy % = 50%
wound % = 50%
depth % = 0%
The check TOTAL says 100%, so my entries are OK. The
values for "index" now represent how well
each cartridge meets my criteria. If I want to see
the order, I can sort the data:
1) Select/highlight the data area by clicking in cell
B5 and dragging through cell N10
2) Select SORT from the TOOLS Menu
3) Click on "No Header Row" in the SORT
dialog box
4) Click on "Column E" and
"Descending" under "Sort By"
5) Click on OK The rows will be sorted best first,
worst last.
To see the effect of using only one
factor at a time, change the weighting for 1 factor
to 100% and the others to zero. Then play with
different combinations that tickle your fancy.
