Browning action

[Echo9]

I feel like there may have been a thread about this not too long ago, but I've been unable to find it.

What is the reason for the Browning type action? Why have the slide and barrel lock together, and then unlock during cycling?

I've been thinking about it, and my theory is as follows:

The straight blowback design works fine and low powered, low pressure rounds, like .22 through .380. The recoil spring must be heavy enough to prevent the slide from flying off the gun during operation, but light enough that the user can rack it. Because these low powered rounds don't require a heavy recoil spring, the straight blowback design is sufficient.

With more powerful cartridges, like 9mm through .45, a recoil spring heavy enough to prevent the gun from destroying itself would also be heavy enough that the user could not cycle the slide. The solution was to lock the slide and barrel together, so that the gasses that cycle the gun must expend a good portion of their energy just unlocking the slide and barrel -- that way the spring only has to be heavy enough for the remaining energy.

Is that close to right? I think there's a few holes in that theory, but I can't fin anything online.

 

[kokapelli]

Being a little on the lazy side I offer this explanation from Wikipedia.

Self-loading automatic pistols can be divided into "blowback" and "locked breech" categories according to their principle of operation. The blowback operating principle is suitable for smaller, low-powered calibres, such as 7.65mm Browning (also known as .32 ACP), and 9mm Browning Short (also known as .380 ACP) as the resistance of the recoil spring and mass of the slide are sufficient to retard the opening of the breech until the projectile has left the barrel, and breech pressure has dropped to a safe level. For more powerful calibres such as the 9x19mm Parabellum and .45ACP, some form of locked breech is needed to retard breech opening, as an unlocked blowback pistol in these calibres requires a very heavy slide and stiff spring, making them bulky, heavy and difficult to operate. A somewhat commercially successful blowback pistol design in the more powerful calibres was produced; the Spanish Astra 400 in 9mm Largo and the similar Astra 600 in 9x19mm Parabellum. All other 9mm Parabellum pistols are locked breech designs.

 

[Steve C]

The gas produced by the fired cartridge is only used for cycling the action in gas operated weapons where some of it is bled off usually from a port near the end of the barrel into a tube that acts on the action either through a piston or direct impingement. Gas operated guns use a locked breach and only open after the gas is diverted to open it. This is one of the ways to delay the opening of the breach until the pressure has dropped.

There a 2 ways to keep the breach of a blow back gun closed long enough to allow the pressure to drop, one is the strength of the spring and the other way is to increase the weight of the bolt or slide. With higher pressure and large cartridges there have been a few blow back operated pistols like the Astra 600 is one of the few that was semi successful. SMG's like the UZI in 9mm, M3, MAC's and the later model WWII Thompson uses a heavy bolt to keep the action closed and regulate cyclic rate.

The locked breach design does the same thing by delaying the opening of the breach but in most pistols the action is recoil operated and not gas operated other than a few exceptions. The locked barrel and slide keep the action closed while the actions moves under recoil which eventually unlocks, opens and ejects the spent case. This allows for a more compact, lighter weight and more powerful pistol.

 

[kokapelli]

Gas operated guns use a locked breach and only open after the gas is diverted to open it. This is one of the ways to delay the opening of the breach until the pressure has dropped.

The Micro Desert Eagle is not locked breach design. The Micro is a blowback action and it uses gas retarding ports to retard the slide opening. You can see one of the gas ports in the barrel in this picture.

 

[rmfnla]

There are a few retarding action designs out there, but the purpose is the same; to delay the opening of the breech until pressures have dropped to a safe level.

 

[Dobe]

And the P7

 

[armchairQB]

All other 9mm Parabellum pistols are locked breech designs.

And the P7

Exactly. P7 uses the delayed blowback feature without the excessively strong recoil spring or heavy slide by using a gas chamber and piston to divert chamber pressure gases to operate on the piston to retrad reward slide movement.