Hi, Art,
I guess I wasn't too clear. There is no locking mechanism in a blowback system, only the inertia of the breechblock. If the bullet does not move, the gas pressure forces the breechblock to the rear and does so very forcibly, since there is no opportunity for the pressure to drop. The case will almost always burst and there will usually be damage to the gun.
The 1911 pistol is a locked breech, recoil operated system, not a delayed blowback. In a recoil operated mechanism, the bullet must move to set the recoil mechanism in motion. Otherwise, the barrel and slide remain locked together. The gas is pushing in all directions equally and if the bullet can't move, the barrel can't move, so the slide can't move. The name is correct; the 1911, Luger, P.38, Glock, etc. are truly recoil operated.
In the case of a no-powder (primer only) load, the force of the primer can move the bullet enough that there is some recoil and movement of the slide in relation to the barrel. But note that the bullet did move.
In most cases, a no powder load will leave a bullet in the barrel and will not fully cycle a normal pistol. But guns set up with a light slide and light spring for pure target will almost always cycle. If the bullet has not exited, the result will be a bulged barrel if the next round is fired.
There is another interesting facet to most SMGs, and that is something called Advanced Primer Ignition, or API. When the bolt closes in one of those guns, a fixed firing pin (STEN, M3, Thompson M1A1) or a driven firing pin (MP38/40 or other Thompsons) strikes the primer slightly before full bolt closure. This means that the blowback force has to overcome not only the inertial mass of the breechblock but also the remaining forward momentum. That is what allows the breechblock to be lighter or have a lighter spring than would be the case if the breechblock were fully at rest before firing. This is why the open bolt versions of the TSMG are easy to operate*, while the semi-auto closed bolt versions take three men and two small boys to cock.
*The original Model 1927 semi-auto is an open bolt gun.
Jim