Having a scope on your rifle or crossbow can greatly increase your accuracy with either weapon. Precision optical sights have become commonplace among both rifles and crossbows. While the scopes for rifles and crossbows may appear similar, and even function in similar fashion, there are significant differences between them.
Rifles are designed to engage targets at much longer ranges than crossbows; consequently, rifle scopes are designed for ranges of 100 yards and beyond, while crossbow scopes are designed for short ranges of 20 to 50 yards. This is the primary reason that the scopes are not interchangeable.
Most crossbow scopes are available with low-power, fixed magnification settings. Crossbow scopes are generally available from one to four power. A one power scope has no magnification qualities and a four power scope magnifies your target four times greater than your normal vision. Rifle scopes typically feature adjustable magnification for short range to long range targets. Perhaps the most common rifle scope is the 3-by-9 power, which gives you a choice of magnification settings between three and nine times your normal vision.
Rifle Scope Reticles
Rifle scopes typically feature crosshair reticles, the intersection of which represents your point of aim. Generally, rifle scopes are sighted in for a distance of approximately 100 yards. Tactical, or Mil-Dot, rifle scopes feature ranging marks that can be used for estimating range to target.
Crossbow Scope Reticles
Crossbow scope reticles are similar in design to rifle scopes, but typically feature descending range marks along the vertical reticle, each representing increasing range. The central aiming point typically is sighted in for a range of 20 yards; each range mark represents an increase of 10 yards. For example, if your target is at a range of 40 yards, your aiming point would be the intersection of the vertical reticle and the second range mark down from the horizontal reticle. If your crossbow scope does not have range marks, you must estimate your aiming point depending on the range.