Stone throwing crossbow

KeithB

Resident Half Fast Machinist
Saw an episode of "Forged in Fire" where the contestants were tasked to build a "stone throwing crossbow". The results looked a lot like a bolt shooting crossbow except it used a pouch to hold a round projectile and had a set of upright posts at the front to stop the pouch and allow the stone to fly free. The limbs were forged steel of traditional design. One of the crossbows was powerful enough to drive the stone into a gelatin casting the size of a human chest and pierce the heart encased within. Wouldn't have shot through armor but it darned sure would lay the hurt on an unprotected soft body part and definitely could penetrate an eye into the brain cavity.

Made me wonder what modern archery technology could come up with. Don't know what a crossbow bolt weighs or fast they can be propelled but I would bet a .45 lead ball could reach black powder pistol velocities if the mechanical parts could be designed and tuned properly.

Any thoughts? Anything historical I'm missing?
 

Ian

Notorious member
Sounds like a Jorge Sprave project. 1000 rubber bands and a laminated wood stock....

The modern .45 caliber air rifles can approach PB pistol velocities but not match them. I'd want to lob something more like a .700" round ball because I don't think a kinetic weapon can get the velocity up very high.
 

Winelover

North Central Arkansas
Crossbow bolts weigh in the neighborhood of 350 grains, not counting the weight of the broadhead. Most common would be 100 grains. X-bows will propel them about 400 fps.................depending on poundage of limbs. Every deer I've shot with my X-bow, was a complete pass through. Unlike my compound, I can not follow the arrow/bolt to the target. My compound would do 200 fps with a 500 grain arrow..............about half the speed of the X-bow.
 

KeithB

Resident Half Fast Machinist
If I remember my physics, energy is 1/2mV^2. Assuming that a crossbow can propel a 400gr bolt at 400 ft/s and that the energy output of the limbs is constant across a reasonable velocity range, then a 125gr .44 lead ball should be able to attain a velocity of about 715 ft/s.

m1V1^2 = m2V2^2

V2^2 = (m1/m2)V1^2

V2^2 = (400gr/125gr) (400 ft/s)^2

V2^2 = 3.2 (160,000) = 512,000

V2 = sqrt(512,000) = 715.54 ft/s

I wouldn't want to catch one up side the head.