A handgun is four times as likely
to be involved in an accidental wounding as a long gun.

Dr. Paul H. Blackman writes:

I believe the discussions on accidents with long guns vs.
handguns sometimes vary from numbers of handguns vs.
numbers of long guns, to numbers of the respective guns
which are regularly stored readily accessible (loaded and/or
unlocked). (Part of the reasoning being that if one assumes
folks will keep a gun for protection, and will keep said gun
loaded, which sorts of loaded guns will do more damage —
are more apt to be involved in injuries, and, if involved,
are more apt to do more serious harm.)

I have seen some discussion along these lines in Kates’ TLR paper.
Unfortunately, Kates is grossly misleading on this topic. If you want to see
whether handguns kept loaded all the time are safer than long guns kept loaded,
then you need to know

  1. What fraction of guns kept loaded are handguns

  2. What fraction of injuries (or deaths) involving guns kept loaded
    are inflicted with handguns.

Fraction 1 is difficult enough to determine. Kates asserts that it is “90% or
more” and that it is “85.2%”. I get a very rough estimate of about
80% from surveys of gun owners storage practices.

There just isn’t any data on fraction 2. Kates instead uses the
fraction for handgun involvement in ALL accidental fatalities, which
he asserts is less than 14%. This is clearly incorrect. People can
still have fatal accidents with guns that are not kept loaded all the
time. Moreover, Kates deliberately mislead his readers when he
claimed that handgun involvement in accidental gun deaths was less
than 14%. In fact, it is about 50%. Most of the time, the type of
the gun is “unknown”. To get his “less than 14%” figure Kates makes the
absurd assumption that NONE of these unknown guns are handguns. If we
assume that the unknown guns are like the known ones, we discover that
about half of fatal gun accidents involve handguns.

I don’t know where the four times more likely comes from.
NEISS data would suggest handguns are involved in over half
of accidental woundings,

about two-thirds

and other data would suggest that
handguns comprise roughly one-third of the stock of
privately owned firearms. Does that work out to four times
the involvement?

Yes. Twice as many wounds, half as many guns, 2×2=4.