GOOD TOPIC!
Ya know it's really impossible to get a handle on 4-H.
They keep changing the rules and on the Nebraska site now is:
Rule 3.3 (b) Sporter Air Rifle: Any unaltered factory sporter air rifle that is or was a catalogue item, readily available over the counter to the general public, weighing no more than 11 pounds, with scope and mounts. Rifles utilizing pre-charged systems of any kind other than 12.0 gram disposable C02 units are prohibited.
---This is the NRA standard & technically this rules out PCP and CO2 rifles such as the 888, 887, and T200.
However they have added:
In addition to any rifle that meets the equipment requirement (3.3b) above, officials will allow the use of any rifle listed as approved for the Sporter 3-Position and the Standing air rifle matches.
So those guns are OK.
Last time in Nebraska (2009 & 2010) they fired indoors so that makes the 888/887 the cheapest rifles to use.
Using a T200 is probably the easiest. You don't need a repeater ... 30 sec a shot is plenty for a single shot & they are used all the time.
You are however, using the rules above able to use some of the older pneumatic (hand charged) Olympic style rifles, but they are kinda heavy for shooters not used to that heavy of rifle. PCP Olympic style air rifles are not in this allowance (i.e. not legal are Anschutz 8002 CA2002, 9003, FWB P-70,P700, P800 etc).
The 4-H event is hard to use the same rifle in 10m 3-P, 10m standing and air silhouette because the silhouette is on the last day and you really cannot get aperture sights off, a scope bolted on & re-zero'd in the small practice session you have between day 2 & day 3.
If at all possible have 2 guns ... one for the 10m events and then the other (like the T200 w/ scope) for the silhouette.
Note that the 888/887 & T200 all have more than enough energy at Rams to kick them over.
If you only have 1 gun to use on all 3 events, leave the gun zero'd after the 10m standing and teach the kids hold overs for each distance .... not optimal, but it can be done if you start practicing it now.
Here is a PDF with paper targets to get started on this .... we were using 4.0 clear front apertures to practice this ... each shooter had their own set with hand drawn adjustments as each rifle is slightly different.
http://vc4hss.com/Air_Rifle/images_AR/8 ... ouette.pdf
It might be boring for them now, but shoot a lot of paper rather than steel to get them in the ballpark.