Back Up Gun definition:

A. Be single or double action.
B. Be either pistol or revolver.
C. Be .32 auto or larger.
D. Have a barrel length:

1. 1. Semi-automatic, 3.8" or less (factory installed cone style
2. barrels with or without a barrel bushing are permitted).
3. 2. Revolver 3" or less.

E. Maximum (total) number of rounds that may be loaded into
the handgun is five (5).

PERMITTED Modifications (Inclusive list):
1. Revolvers:
A. Sights to another conventional notch and post type (see
"sights" in glossary for further information).
B. Grips to another style or material that is similar to factory
configuration (no weighted grips).
C. Action work to enhance trigger pull as long as safety is
maintained.
D. Bob hammer spur.
E. Chamfer cylinder.
F. Custom finishes.
2. Pistols:
A. Sights to another conventional notch and post type (see
"sights" in glossary for further information).
B. Grips to another style or material that is similar to factory
configuration (no weighted grips).
C. Slip-on grip sock and/or skateboard tape.
D. Action work to enhance trigger pull as long as safety is
maintained.
E. Reliability work to enhance feeding and ejection.
F. Internal accuracy work to include replacement of barrel with
one of factory configuration (factory installed cone style
barrels are permitted).
G. Custom finishes.