Originally Posted by Shadow9mm
I am still struggling to understand the difference between straight blowback and delayed blowback, as the mass of the slide is used to delay the opening of the firearms. It is still a function in the design of the firearm, despite not being a separate mechanism like a roller lock. would not that still be a very simple delaying mechanism, thus qualifying it as a delayed blowback?
Again...no. The confusion seems to be from where you are applying the term "delay". So, lets try and clear that up.
Every firearm holds the breech shut when the round is fired. AND they hold the breech shut for a brief period of time AFTER the round ignites. The time required for the bullet to leave the barrel, and the pressure to drop to a level safe to release into the action when it opens.
This is NOT "delay". It may seem like it, and from a pure linguistic point of view it is "delay" because the breech does not open the instant the round fires. But the breech is not supposed to open the instant the gun fires (that would be dangerous) so the time interval between firing and opening is not considered a "delay".
The time lag between the cartridge igniting and the action opening is a required, necessary part of firearm function. It MUST happen or you get a face full of high pressure gas and probably brass fragments.
Since that must, and does happen with EVERY GUN, every time it fires, it is not considered a delay, it is proper operation.
SO, now more specific, to blow back and delayed blow back.
You understand the blowback holds the breech shut for a brief period of time (as designed for safety) using inertia and spring tension. Bolt mass and spring tension are calculated and balanced against the force of the gas pressure so this happens.
A delayed blowback (aka retarded blowback) does the same thing, BUT uses something to slow down the opening of the breech so that it opens after it would with a straight blow back system.
This is most often done with a dimpled or fluted chamber, which means the brass case grips the chamber slightly longer before releasing, which means the blowback is slightly delayed in time from when it would have opened without the fluted chamber (or whatever system is used).
IN effect it holds the breech shut LONGER than a straight blowback. It delays the opening COMPARED TO a straight blowblack action.
This is done to allow the use of higher pressure rounds than the straight blowback can handle and/or to allow the mechanism to be "differently balanced" against the gas force, and achieve safe, reliable function.
As an example, lets say we built a blow back gun for round X, and in order to hold the breech shut long enough, the bolt has to weigh 2 pounds to have the inertia needed.
Now, if we retard the blowback, spreading the "push" from the powder gas out over a longer period of time before movement happens, by using something like a fluted chamber, we can tinker with the balance of forces.
Meaning that bolt mass (and spring tension on it) may be adjusted (changed) and still do the job needed. IF a straight blow back needs a 2lb bolt to work, a delayed blowback system may only need a 1.5lb bolt in order to work with the same pressure cartridge. (numbers for illustration purposes only)
This allows designers the flexibility to either make the gun ligher, or keep it where it is for mass, and use a higher pressure round.
The designs not only have to work, they also have to be light enough that people will use them.
SO, a delayed blow back is only "delayed" in comparision to when a straight blow back would open. ALL guns are 'delayed" from opening the instant the cartridge ignites, by intentional design and therefore are not considered "delayed".
Clear as mud now??