If your only range is 100 yards, you can still challenge yourself, but you need to get off the bench.
You can do the NRA Service rifle course of fire at 100 yards with reduced targets. I attached printable versions of the SR1 (used for Standing and sitting) and the SR21c (used for Prone rapid fire)
I posted the MR31c (for slow fire prone) here:
http://thefiringline.com/forums/showthread.php?p=4236230#post4236230
The SR1 is reduced from 200 yards, the SR21c is reduced from 300 yards, and the MR31c is reduced from 600 yards.
Print them on a standard sheet of 8.5x11 paper and get to shooting. Your 1903a3 would be a good rifle for it, and it already has the proper sling.
The course of fire is generally 2 sighters, and 10 (or 20 depending on the club) shots for record per position.
1. Slow Fire, standing - 10 rounds in 10 minutes. (SR1 target)
2. Rapid Fire, sitting or kneeling - 10 rounds in 60 seconds. (SR1 target)
3. Rapid Fire, 10 rounds prone - in 70 seconds. (SR21c)
4. Slow Fire, 10 rounds prone - in 10 minutes. (MR31c)
Good overview of the positions here:
http://www.shootingusa.com/PRO_TIPS/USAMU3-5/usamu3-5.html
I added a gray pattern to the targets to make spotting bullet holes easier. The grey is not visible from distance, they just looked like standard black bullseye type targets when using the iron sights, but with even minimal magnification you can see bullet holes because they break the pattern.