At 100 meters range, that would be perfect of a small bore (rimfire) silhouette range. Your 6" 617 would be fine for that.
I've never seen a big bore setup on less than 200 meters, so I can't comment on your situation.
H. Range Layout / Target Set-Up
1. A silhouette range consists of a firing line and four different target lines,
one for each of the four animals (chicken, pig, turkey, ram). Distances from
the firing point to each bank of targets shall be:
Big Bore Small Bore, Field Pistol Air Pistol
Chickens 50 M / Yd. 25 M / Yd. 10 Yd.
Pigs 100 M / Yd. 50 M / Yd. 12.5 Yd.
Turkeys 150 M / Yd. 75 M / Yd. 15 Yd.
Rams 200 M / Yd. 100 M / Yd. 18 Yd.
Tolerance +/- 5 M / Yd. +/- 2 M / Yd. +/- 6 Inches
http://www.ihmsa.org/2009%20rulebook%20final.pdf