If you prefer your scopes compact without functionality compromises, the Delta Armory 3-9x40 Illuminated Short Rifle Scope should be right up your street. This variable magnification rifle scope measures less than 20cm in overall length, making it ideal for platforms with less rail space needing a long-range optic. 
 
Features
Aluminium construction - Glass lenses, alloy scope rings
Very short overall length - Great for platforms with limited rail space
3-9 x Magnification - Great for DMRs and Snipers, use 3x for engagement and 9x for spotting
25mm Monotube - Compatible with aftermarket 25mm monotube mounts
25mm Scope rings for 20mm Picatinny rails included - Ready to mount!
Red or Green reticle colour options - Set the reticle colour to suit your environment
5 Brightness settings for each colour - Use the brightest in bright sunlight, dimmest in low light
Radial magnification adjuster - Surrounding the "eyebell" at the rear, easy to adjust thanks to its knurled surface
Windage and elevation adjustable - Windage dial on the right, elevation dial on the top 
Capped adjustment turrets - Unscrew the caps to access the dials, adjust by hand or using a flathead screwdriver
Battery compartment inside the magnification adjustment dial - Unscrew the top cap to access
Battery: 1 x CR2032 3V Button Cell (included)