Quote Originally Posted by Bruce_in_Oz View Post
Remember that early SMLEs used a striker that had a lug which lined up with a notch in the rear of the bolt head. This was to ensure that if the bolt was not closed fully, the striker could not ignite a cartridge and do some serious damage.
The lug on the firing pin & the notch in the bolt head are aligned the moment you clip the bolt head down onto the bolt head rail, neither the bolt head or the firing pin rotate while working the bolt, if the bolt is not closed properly when fired, it either closes fully itself or go's into the "half cocked" position.