stonebow

[markdem]

Otherwise known as a pellet/bullet shooting crossbow. I built this thing to see:
A) how accurate are they?
B) how fast do they shoot?

What I've learnt is that these things are super finnicky! I've shot paintballs with insane ball-on-ball accuracy at 25 yards, then tweaked the string/pouch and had paintballs fly way off target. On a semi-interesting note, paintballs don't suffer from the magnus effect because there is no barrel to impart spin, so they fly very straight. Sights are more of a necessity than I had expected. There is no long, straight barrel to point at your target so sights are a must. The rear sight is static. The front sight is fully adjustable.

I dont have chronograph readings but my guess is that paintballs travel at around 200fps. that speed would obviously change depending on what limbs the crossbow has (this one is powered by cross-country ski's)

[hectmarr]

Nice work, congratulations! I love crossbows, maybe I'll ever try to build one. It is interesting what you comment on the precision of the balls in the absence of a firing cannon, and the magnus effect.

[jackssmirkingrevenge]

Very clean work, kudos! Nice repurposing of the skis

It doesn't seem like it takes a lot of effort to cock. Have you tried something heavier than paintballs?

[markdem]

if i had to take a guess, i'd say the draw force is around 30-40lbs. I can use downhill ski's to double the coking force, but I'm effectively dry-firing the crossbow when shooting lightweight paintballs which puts a shitload of stress on the string and limbs. I havnt shot any metal/clay projectiles yet, but from what I read on other websites, the velocity doesnt drop much. I'd relate it to a big diesel truck: slow but torquey

[jackssmirkingrevenge]

I havnt shot any metal/clay projectiles yet, but from what I read on other websites, the velocity doesnt drop much. I'd relate it to a big diesel truck: slow but torquey

Essentially the velocity of the string is the velocity of the projectile, so you need a heavier projectile to better exploit the available energy.