I have been using Semi-circular Arrowheads for the last 5 years in Bele. They have failed at two events for the template rule (Chaos Wars XV and Battle for the Ring VI). The tip of the arrowhead emerges through the 2.5" hole the most marginal amount. I believe that semi-circular arrows should not be failed for this rule.
My argument is based upon the fact that we already make a rule concession for swords with a semi-circular tip.
Book of War wrote:1.3.3. Two and one-half inch rule-No surface on a striking edge (sword tip, arrow head, spear head, javelin head, etc.) whether designed for stabbing or not, may readily pass more than 0.5 inch through a 2.5 inch hole; swords with a semicircular tip, with a minimum 1.5 inch radius are exempt from this rule
Photo for reference
Kyrian and I came up with some basic guidelines for checking round-headed arrows, which would only require a small addition to the BoW.
"Arrows with semi-circular tips must not readily pass more than 0.5 inch through a 2.0 inch hole."
I believe this to be in the spirit of the rules as well as something to easily reference.
Thoughts?