Here is the scoring rules from the NRA bulls eye rule book:
14.3 How to Score - A shot hole, the leaded edge of which comes in contact with the outside of the bullseye
or scoring rings of a target, is given the higher value (Fig. F). A scoring gauge will be used to determine the value
of close shots. The higher value will be allowed in those cases where the flange on the gauge touches the scoring
ring. No scoring gauge will be used unless the diameter of the scoring flange is within these limits:
.22 caliber .2225" - .2240"
.32 caliber .310" - .314"
9mm & 38Spl .355" - .359"
.40 caliber .397" - .401"
.44 caliber 426" - .430"
.45 caliber .450" - .454"
Devices other than scoring gauges may be used to assist in establishing the correct value of hits. These
devices are not to be inserted into the bullet hole and do not constitute a scoring gauge.
(a) In case of keyhole or tipped shots, the higher value is awarded if the leaded edge of the bullet hole
touches the scoring ring of higher value, even though the hole is elongated to the bullet's length rather
than being a circle of the bullet's diameter.
(b) In case of skid shots, the higher value is awarded if the leaded edge of the bullet hole touches the scoring
ring of higher value, except the value of a skid shot may not be more than one ring higher than the original
point of bullet contact with the target. The target shall be defined as the entire card or paper on which the
scoring rings are printed but shall not include the backing. When the original point of bullet contact is on
the target card, but outside the scoring rings, and the leaded edge of the bullet touches a scoring ring, it
will be given the value of the lowest scoring ring.
(c) When a bullet enters a target from the back side it will be scored as a miss.
14.3.1 Authorized Use of Plug Type Scoring Gauges - The use of the plug-type gauge will be restricted to
use by range operating personnel who may include the Range Officers or Block Officers, Pit Officers, Match
Supervisors, Statistical Director, Match Director, Jury or Referee, as appropriate to the type of tournament
concerned. No competitor will use scoring plugs of any kind on 29 a target at any time. Where targets are scored
on the range only the above designated officials may use plugs to check values or determine the outcome of
challenges. However, competitors acting as scorers may use official NRA overlays in the performance of their
duties. The tournament program should state in the Match Conditions Section by whom and under what
circumstances plug-type scoring gauges may be used.
14.3.2 Removal of Plug Type Scoring Gauge -
(a) The plug type scoring gauge, if used, will remain in the shot hole until the shot value is agreed upon by the
competitor and the scorer, or until removed by the Referee, Jury or Supervisor after a challenge. If the
plug type scoring gauge is removed prior to an agreement of shot value, the shot hole may not be
re-plugged and must be taken to the Referee, Jury or Supervisor for final decision.
(b) Only the Referee, Jury or Supervisor may use a plug type scoring gauge to determine if a shot hole is a
double.
14.4 Misses - Hits outside the scoring rings are scored as misses. (Except as provided in 14.3(b).