I haven't had an entry level Hawke on a springer, but UTG/Leapers are priced appropriately and have held up well for me. I have a 3-12x40, a 4-16x40, a couple 6X Bugbusters, and none have crapped out on me yet.
100 yards is too much for a .177 springer, unless you'll be satisfied with 4" groups. .177 is generally good out to about 55 yards, same with springers, in general. With a nice .177 PCP, you might get 3" groups @ 100 yards.
If you want to try it anyway, get something with a high enough magnification that you'll be able to see your target reasonably well at 100 yards.
In my opinion though, stick with 55 yards and under, and just shoot at smaller targets if you want more of challenge. Focus on hold your gun the exact same way every time. Generally speaking, not too tightly to your shoulder, not gripped too tightly, not pressed against your cheek too tightly, and just supported underneath the fore stock from kind of a soft rest. That's what works best with my Benji nitro piston rifle. I get about 1" groups at 35 yards as my best, with the average being closer to 2".
