Gun Tech: Smith & Wesson Tempo Barrel System

The .22 Winchester Magnum Rimfire (WMR) was designed in 1959. Today, they are typically loaded with 30- to 50-grain bullets traveling between 1,500 and 2,200 feet per second (fps). Maximum pressure for the .22 WMR is listed as “24,000 psi” by the Sporting Arms and Ammunition Manufacturers Institute (SAAMI). The .22 Magnum benefited from the KelTec PMR30 (2011) and Rock Island XT 22 (2018), but the recent Smith & Wesson M&P 22 Magnum has reignited interest in the .22 WMR for defense. Of course, availability of purpose-built ammo — Hornady’s Critical Defense 45-grain FTX load, for example — has helped its popularity.

The 5.7x28mm was developed for NATO by FN in 1990 for use in the P90 personal defense weapon (PDW). It was also chambered in the Five-seveN pistol, last updated in 2023. The cartridge was designed to be capable of penetrating soft body armor and was intended to supplant the 9mm, but it never did. Commercial offerings are not armor piercing. Loaded with 23- to 40-grain bullet weights, 5.7mm projectiles travel between 2,350 and 3,060 fps from a 10-inch barrel. The 5.7mm is a bottleneck cartridge with a maximum pressure of 50,038 psi. In 2020, the Ruger-57 was introduced, followed by the launch of the KelTec P50 and Smith & Wesson M&P 5.7 handguns, not to mention several carbines and commercial loads from Federal, Fiocchi and Speer. Once again, interest in the 5.7 was piqued.

The capacity, price and high performance for the relatively low felt recoil attracts a lot of shooters to consider these pistols for self-defense roles. The 5.7x28mm and .22 Magnum produce different chamber pressures, though, so Smith & Wesson had to engineer a different two-piece Tempo barrel and sleeve for each model. The M&P 5.7 required a locked breech and a delay in cycling, so a rotating barrel was designed to allow pressure to drop before the lugs rotate, unlock, and continue with extraction, ejection and feeding. The M&P 22 Magnum features a gas-assisted blowback action due to the lower pressure of the .22 Magnum. Aside from the pressure difference — and that the M&P 5.7 has a rotating barrel — both have a small port near the muzzle The gas escapes the bore and enters the barrel shroud, not the slide. The barrel acts as a piston, while the barrel shroud is effectively the cylinder. The size of the gas ports are different for each cartridge — 5.7x28mm being larger — to optimize performance in each platform.

When the M&P 5.7 is fired, the barrel remains locked at the breech until gas from the fired round reaches the gas port. The gas pressure on the barrel forces it rearward into a cam surface in the shroud, causing the barrel to rotate and unlock from the slide. There is no tilt-barrel on the M&P 22; it is a blowback design.

Lighter recoiling when compared to a similar size-and-weight pistol chambering 9mm, the M&P 5.7 features slots specifically designed to reduce the slide’s mass to ensure reliability across the spectrum of bullet weights and use of the pistol with optics. Reliability could be affected by shooting lightweight ammo loaded with 20-ish-grain, sintered, frangible or polymer-type projectiles. Results may vary with some of these uncommon loads. Besides these bullet types, reliability is excellent. The clever engineering behind the Tempo barrel system provides shooters with a more comfortable shooting experience that is easy to operate and maintain. The Tempo barrel system ensures the right timing for each cartridge, resulting in a consistent extraction process and less recoil. There was no need for a stiff recoil spring, which also means that the slides are easier to rack. The frequent need to reload is also reduced given that both models use magazines with either 22-round (5.7mm) and 30-round (.22 WMR) capacities.

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