Also known as: windage.
| Windage | The clearance between projectile and bore |
|---|---|
| Problem | Escaping gas wastes force and hurts accuracy |
| Obturation | Sealing the bore, as by a sabot or expanding band |
Sealing the bore
Smoothbore guns needed clearance, or windage, between the round shot and the bore so the ball could be loaded, but that gap let propellant gas blow past the projectile, wasting force and letting the ball bounce down the bore to leave the muzzle less predictably.
Obturation, the sealing of that gap, was one of the central improvements of Civil War ordnance. Expanding sabots and bands on rifled projectiles sealed the bore behind the projectile, capturing the full force of the charge and improving both range and accuracy.
On this site
Sources & further reading
- Benton, James G. A Course of Instruction in Ordnance and Gunnery. 2nd ed. New York: D. Van Nostrand, 1862.
- United States Army, Ordnance Department. The Ordnance Manual for the Use of the Officers of the United States Army. 2nd ed. Philadelphia: J. B. Lippincott, 1862.