Disappointing
![Confused :?](./images/smilies/icon_e_confused.png)
I thought about how to build a blow back that actually work and came up with this idea.
The actual design features a back - forward bolt with a QDV as a main valve.
![Image](http://img51.imageshack.us/img51/293/backforwardbolt.jpg)
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The blow forward moves first, due to the weaker spring and has less space to travel than the blow back that pushes back a stronger spring. When the pressure in the "firing chamber" overcame both springs three things happened:
1. the hammer was cocked
2. the QDV closed
3. and the projectile was fired
(in my theory)