Blowback operation is a method of operation for autoloading firearms. It is almost always found on smaller-caliber handguns, although some more powerful pistols use the same mechanism. The major task of a semi-automatic firearm is to utilize the energy from each round (at least partially) to prepare the gun to fire the next one. This means it must, as a rule:

  • Eject the current empty shell
  • Cock the hammer or striker
  • Strip a new round from the magazine
  • Load the new round into the chamber
  • Return the firearm to the initial state.

There are several general ways of handling these tasks, including gas-operated, short recoil (made famous by John Moses Browning) and blowback. This is the simplest. In a blowback operated gun, the recoil from firing pushes the operating part of the gun rearward. This will always include the bolt; the barrel (and thus chamber) and usually the barrel housing (as there is no slide) of the gun are locked in place. The shell casing slides backwards out of the chamber under the impetus of the recoil and is ejected. At the rear of the cycle, the reciprocating parts of the gun (again, usually in a blowback pistol, the barrel and slide are locked together and integral so this means the bolt) will cock the action and then the recoil spring will push them forward to reload and reset the firearm.

The advantages of this method center around its simplicity. There is a single back and forth action, and a single large spring will handle the reset.

Disadvantages there are as well, though. Because the entirety of the recoil is essentially passed to the shooter's wrist, albeit sometimes delayed by the spring action, more powerful handguns may be much harder to control if they are blowback operated (Although guns like the Hi-Point .45 exist, who knows why). In addition, the barrel and bolt are not locked together (or the latter wouldn't be able to recoil). So strong, sharp movements of the gun can move the bolt out of battery, especially with weaker recoil springs. In addition, blowback firearms tend to spit more gas and powder residue rearward and sideways, as the case comes out of battery quickly rather than recoiling with the barrel and bolt locked together - the latter tends to see much more of the ejecta sent forward out of the barrel.

This describes the simple blowback mechanism, as there is no provision to mitigate or delay the recoil forces once the gun has fired (other than whatever can be mitigated by the bolt and recoil spring and thus absorbed by the cocking action). There are all manner of means of delaying the blowback operation, and firearms that use those (regardless of which) are generally called delayed blowback.

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