1968 MP5 with no serial number

[Peter Laidler]

Now you're asking......... Taking me back to my teaching Physics days..... Nope, it's a bit more than that...... But the rearward loading on the BB will mechanically force it rearwards of course but a part of that rearward force will attempt to lift the rear of the BB by virtue of the (relatively small) inclined angles of the locking bent of the BB against the same inclined angle of the l/shoulder. However, this mechanical inclination of the BB to lift - due to the two inclined angles mentioned - is thwarted by the more substantial area of metal to the rear of the locking bent in/at the inside rear top of the BBcarrier. In turn, the BBcarrier is held downwards against this upwardly directed loading by the sliding ribs

Are we all still here - or have we all gone into a deep slumber? Right, while the BBcarrier if out of the rifle, I want you to have a look inside at something more interesting. It's sounding more like a school physics lesson now......... Look at that LOCKING BENT ramp thing at the rear of the inside of the BBcarrier. Got it? Notice the approx 1/2" distance it extends to the rear from the ramp part. This is the locking shelf (or locking medium in technical terms) and is a VERY important feature of the mechanism. As the BBcarrier is pushed rearwards by the piston, this long 'shelf' ensures that while the piston and BBcarrier is pushed rearwards, the BB remains positively locked downwards ahead of the locking shoulder. for a further 1/2" or so This one part of the inbuilt mechanical safety.

But there's more. You'll now see that the BB can't start to LIFT out of LOCK (called commencement to unlock - which isn't the same as 'unlocked' of course) until the BBcarrier has moved rearwards by approx 1/2". And by then, the rear of the striker is shielded. The same thing but sort-of in reverse happens when the BB and BBcarrier goes into lock down. But now, the rear of the striker is not accessible to the hammer until the BB is locked AND the BBcarrier is almost fully forwards.......... But there's more.......... If by your quick action of the trigger (or in the auto role) you do release the hammer before the BBcarrier is FULLY forwards, the hammer will cam forwards more slowly............... anyway, you'll get a misfire due to what is called 'diminished force of blow of the striker'

Wake up at the rear of the class...............