Hmm...
According to the NRA rulebook, the B-39 has no dimensions...
See
Section 4 of the
NRA International Pistol rulebook.
However, the USAS rules define the 50 foot Rapid Fire target dimensions under rule USA 6.3.2.4B:
10 ring 58.75mm (+/- 0.2mm)
9 ring 107.52mm (+/- 0.2mm)
8 ring 156.29mm (+/- 0.5mm)
7 ring 205.06mm (+/- 0.5mm)
6 ring 253.83mm (+/- 0.5mm)
5 ring 302.59mm (+/- 0.5mm)
Inner Ten = 28.27mm(+/- 0.2mm).
Black from 5 to 10 rings = 302.59mm.
Ring Thickness: 0.5mm to 1.0mm.
Minimum visible size of target card: 335mm x 335mm
(13.2 x 13.2 inches).
Scoring ring values 5 - 9 are printed in the scoring zones, in vertical lines only. The 10 point zone is not marked with a number. The zone numbers shall be approximately 6mm high and 0.5mm thick (see Figure 4). White horizontal aiming lines replace the ring values at the left and the right side of the target center. Each of the lines is 75.65 mm long and 3.03 mm wide (see Figure 4).
You can find the USAS rules at:
USA Shooting Rulebooks
Look at the Technical rules for target specifications.
Take Care,
Ed Hall
US Air Force Shooting Teams
Bullseye (and International) Competition Things