Closed bolt

• More accurate for the first round and for semi-automatic fire:
  • No movement of heavy working parts prior to firing to potentially inhibit accuracy.
  • Round sits consistently in the chamber.
  • Potentially shorter delay between operator pulling the trigger and round being fired (also known as lock time).
• Cleaner operation – less potential for dust and other foreign debris to enter the gun, since the action remains closed unless the weapon is firing.
• Action can be locked forward to further reduce noise in a suppressed weapon.
• Can carry an additional round in the chamber, increasing ammunition capacity to one beyond the magazine's limit.

• More complicated and expensive to manufacture.
• Less heat dissipation from closed chamber (increased danger of cooking off)
• The extra round in the chamber can be a safety hazard, as even when the magazine is removed, the round in the chamber will still be ready to fire, and must be manually ejected.

Closed-bolt designs are often used in rifles. The improved accuracy of closed-bolt weapons is more desirable, while the poorer heat dissipation is less of an issue for slower-firing weapons. In contrast, open-bolt designs are more often used in automatic weapons, such as machine guns. For fast-firing automatic weapons, heat will rapidly build up from sustained firing, but accuracy is of less importance. Thus, the improved heat dissipation of open-bolt designs is generally more desirable in automatic weapons.