level 11
贴吧用户_023MZ1M
楼主
The breech block rides on the piston extension; locking is accomplished by a ramp at the rear of the piston extension which forces the rear of the breech block upwards When the round is correctly chambered, the rear of the block is able to move into a recess in the top of the body The piston goes further forward and the ramp rides under the block, holding it up into position in the locking recess in the body. Mechanical safety before firing comes from the non-alignment of the firing pin and cap until locking occurs. The free forward travel of the piston post after locking is completed before the front face of the piston post, acting as a hammer, contacts the firing pin. Mechanical safety after firing is provided by the position of the gas port and the free travel of the piston post before the inverted ramp pulls the block out of engagement with the body.
The same principle is applied to the L1A1 rifle which was derived from the FN FAL rifle, shown in Fig. 10.12. Here the forward movement of the carrier forces the rear of block down in front of a locking shoulder in the body and then the carrier overrides the bolt to hold it locked. After firing the piston forces the carrier back and the unlocking ramps strike the breech block bents and lift the locking bent out of engagement with the body. Mechanical safety before firing comes from the non-alignment and shrouding of the firing pin. Consequently the cap cannot be struck until locking is completed. Until the carrier is fully forward (i.e locking is completed), the hammer cannot rotate since it is held up by a safety sear operated by the carrier.
The two previous examples have been of weapons in which the block has tilted in the vertical plane and both of them have been rear locking. The Czech Vz 52 SL rifle is an example where forward locking is employed. This is not quite so easy to achieve and can lead to extraction difficulties.
![[开心]](/static/emoticons/u5f00u5fc3.png)
