800-1100 or so.
I doubt it.
It's rated at 580 FPS.
300 fps or 320
It's rated at 660 FPS
Depending on the size of the animal. Then yes it can with a good head shot. If the animal is too big it may not kill it, and then you have one very mad animal at you.
For a air soft BB gun it's okay not powerful. For a regular BB gun "NO" that is not powerful at all. A Daisy Red Ryder BB rifle will fire around 325 FPS most new pellet Air Rifles will fire at least 1,000 FPS. A really good Air soft rifle will get around 500 FPS.
With the draconian UK laws, any legal - non FAC - air rifle will not exceed 750 fps. With 11 ft/lbs and a pellet weight of 28g will give a velocity of around 420 fps. A FAC rifle with 40 ft/lbs and a pellet weight of 28g will give a velocity of around 800 fps. The .22 FAC Theoban MFR will produce 28 ft/lbs which equates to only 671 fps. So even if you have an FAC certificate, the chances of finding a rifle with at least 35 fps is slim, but not impossible.
Unfortunately this rifle is not worth repairing. In Excellent condition it is worth $18. It has an FPS of 250 FPS. That's slower than a Daisy Red Ryder. I really suggest you purchase a new air rifle. These air guns were not designed to be repaired. Marksman is owned by Beeman. If you want to try I suggest you call Marksman at 800-822-8005
This Chinese air rifles shoots about 615 FPS. This is average for this type of air rifle.
375 FPS
The Marksman BB 2020 Buddy rifle is rated at 300 FPS