IMHO, a regular monthly "Sanctioned" shooting event requires way to much effort and time on the part of the organizers. It will get old very fast.
I'm uncertain as to what your goals are but, if it was me, I'd offer a variety of up to 6 non-sanctioned events a year on Saturday mornings that run May-Oct. Most shooters out there don't really care to compete, but may be interested in a "just for fun" organized shoot where they can challenge themselves and receive a "trophy" for participating, or ranking in the top 20%, or something along those lines.
We've done some of these at our club several times over the years.
1. .22 rimfire rifle shoot - 3 position standing/seated/prone (or rested) hit count on steel targets at 3 distances or same distance with smaller steel.
2. Carbine shoot - any semi-auto rifle IPSC targets, timed, 30-50 yards, Standing 10 rounds - transition to 10 rounds seated with mag change - transition to 10 rounds prone with mag change. Depending on how many shooters you have, participants can run it two or three times.
3. Ground Hog shoot - 100-300 yards, paper ground hog targets, Scoped centerfire rifles, Bench rest or prone (shooters choice). 20 rounds in 25 minutes at two different distances. up to 5 sighters and 10 rounds for score at each distance.
4. Black Power shoot - Percussion and Flint lock Rifles and pistols. There are a lot of options here. We've found that shooting at steel at 30-40 yards is a lot of fun.
5. CMP/NRA High Power non-sanctioned shoot - We hold these monthly May-Nov at our club. It's just for fun, any rifle scoped or iron sights. Everyone is just competing against themselves, no awards or prizes.
6. Military Rifle shoot - 3 position any rifle that was used by any nations army bolt & semi auto. You may include or exclude AR's. Make up the COF.
2-3 hours max for these events. Any longer and it will drag.
Myself and several of our members would participate in many of these if you held them. :cool:
BTW, have lunch afterwards for the participants (donation). Hotdogs/Baked beans/pop. BSing at the range is half the fun!