Here's a Knex sniper, it's rather good in my opinion.
Step 1: Hopper and Barrel
I should give some credit to The_Burrito_Master for the concept (I have permission :P). I have modded it slightly.
Step 2: Pin Guide and Handle
Step 3: Butts
Yeah I got lazy. The pictures are clear enough though, this is an easy step.
You can choose between the 2 butts.
If you are building the pistol, then check the last picture for reference.
Step 4: Put the What You've Made Together
Step 5: Barrel
Time for that long barrel :D
Step 6: Other Bits
1) Iron Sights
2) Rails (make the gun stronger)
3) Hopper cover (highly recommended)
Step 7: Monopod
Uses a ratchet system. Push the yellow bar to unlock and use, otherwise it locks and doesn't move! Great success!
You can design your own monopod base if you like, I prefer the simple option.
Step 8: Firing
1) Load 6 red rods into the mag
2) Shut lid
3) Pull back the pin slide until the gun clicks
4) Pull the true trigger (or if you want push the block trigger)
If the shot fails (very rare), the gun is installed with an access hole so the bullet can be pushed back into the firing slot easily. The hole is located above the barrel.
Step 9: Coming Soon...
True bolt action pistol :D