Here is a track profile and guide “shuttle” that could give more
consistent bolt path. However the shuttle must support and center the bolt at
rear and have an arrow rest at front of the tiller. In other words these balls
or arrows never contact the track. A gap is provided between shuttle bottom and
track. My activator or”wippe” fits the shuttle exactly so the bowstring is
always drawn back the same. Use of a projectile shuttle is an ancient idea, but
I came up with this design after experiments with round shuttles and “V” groove
tracks were disappointing.
Below is a removable ¼” high track on my ball shooting
crossbow. The track is attached using Loctite spray adhesive and has survived
thousands of shots. Note the blue lexan ball retainer; it swings up as the shot
is fired. Of course at this low velocity the balls do not make clean holes so targets
are 1 shot each at 12 bulls designed for army small bore training. Ammo is
.375” steel and .400” lead seated in a conical socket. The consistent shot placement is well beyond
my hand held ability.