Inserts & Bore-Matching

Barrel inserts are thin sleeves that fit inside an outer barrel body to define the effective bore size. Instead of buying multiple full barrels, players can use a single outer shell with a set of inserts covering a range of internal diameters. This approach reduces cost and weight while still allowing fine control over how tightly paint fits in the barrel.

Bore-matching describes the practice of choosing a barrel or insert diameter that pairs well with the current batch of paint. A simple field test involves gently placing a paintball into the barrel or insert: if it rolls through freely, the bore is likely larger than the paint; if it sticks with modest resistance and can be pushed through with a light puff of air or a gentle blow, the bore is close to or slightly smaller than the paint’s diameter.

Slight underboring (where the barrel is a bit smaller than the paint) can help seal air behind the ball, improving consistency and air efficiency. Moderate overboring (where the barrel is larger than the paint) may be used when paint is fragile or inconsistent in size, reducing barrel breaks at the cost of some efficiency. Extreme mis-matching in either direction can lead to broken paint or erratic flight paths.

Factors such as paint brand, storage conditions, humidity, and temperature all influence paint size. For this reason, many competitive players test and select inserts before each event day. Proper bore-matching works in combination with stable chronograph settings, good paint quality, and sound marker maintenance to produce accurate and predictable shot patterns.