A Straight-Pull Bolt is an alternative loading mechanism to the original turn-bolt design in the category of bolt-action guns. It features, literally, a bolt that is pulled straight back to empty the firing chamber, the bolt is then simply pushed back into its original position to load the next round. This is done as opposed to turning the bolt, then pulling it back, pushing it forward, and finally turning it back into the position it started in.
"A Straight Pull Bolt allows the Recon soldier to chamber another round in his Bolt-Action sniper rifle without having to first zoom out."
— Battlelog description
In Battlefield 3 the Straight-Pull Bolt is an attachment for any and all bolt-action rifles. When attached to a bolt-action rifle, the straight-pull bolt allows for the shooter to chamber and then fire another round without being required to leave the scoped view as normal. However, the attachment does change & edit the animation of cycling the bolt to load the next round from the magazine.
The Straight-Pull Bolt didn't function properly in the Battlefield 3 Open Beta. In the beta, the straight-pull bolt still required the user to zoom out to load and chamber the next round into the action of their rifle. This problem made the attachment ineffective and therefore useless to all of its users for the duration of the Open Beta.