it's mostly a lack of demand. 45 and 9mm are the two most prolifically used handgun calibers out there along with 357 and 38 special on the revolver side.
the 40 S&Ws and 44 mags have enough demand that companies continue to crank them out at decent speeds while few enough people use it to instantly clean up shop when a scare like this hits. case in point which may vary per person.
in a 15 mile radius among family members (anti 1911s)
I now own 2, 9mms and 2, 45ACPs
my bother owns 1, 40 cal and 1, 45ACP
my brother in law owns 2, 9mms
a LEO buddy owns 2 40 cals, 1 45 and 2 9mms(glock snob).
so in my family of avid gun enthusiasts there are
6 9mms total
4 45 ACPs total and
3 40 cals.
none of us shoot 1911s mind you so some people are bound to have much more in the way of 45s but you see the correlation in the demand placed on those calibers. notice that calibers like 25 ACP, 32 AUTO, and 10mm were barely even affected by this latest scare, the number of people to create the demand is directly proportionate to the number of people removing the supply...
I have no idea if that rambling even had a point but I added my .02 and that's that.
all guns lost in a tragic smelting accident.
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