Semi-Autos Produce Lower Velocities Than Revolvers

by
posted on March 1, 2013
** When you buy products through the links on our site, we may earn a commission that supports NRA's mission to protect, preserve and defend the Second Amendment. **
bs_2015_fs-1.jpg

The Myth
Semi-autos produce lower velocities than revolvers or fixed-breech guns because some of the gas is used to cycle the action.

The Facts
For this myth, we'll refer to the NRA Fact Book, aka The BullShooters Bible, because Julian Hatcher and his mathematical-minded cronies are smarter than me.

In a nutshell, The NRA Fact Book reports that semi-autos produce less velocity than fixed breech guns "is true to a very limited extent, the difference is of little importance in practical shooting terms. Determining the magnitude of the effect is not simple, because it is often less than the expected variation of velocity from shot to shot."

It must also be noted that another factor in velocity is the weight of the gun as it relates to its backwards recoil energy upon firing. The recoil of the gun subtracts from the bullet's velocity. Taken to the extremes, an unmovable, fixed-breach gun bolted to a bench allows 100 percent of bullet velocity to be reached, while a gun weighing equal to the projectile would allow 50 percent of bullet velocity to be reached; the other 50 percent would be directed backwards with the gun.See the following table:

Fixed test gun: 950 FPS

Target Pistol (36 ozs.): 948

Light Pistol (30 ozs.): 947

Breechblock Only (6 ozs.): 937

The Surprising Truth
Much more significant, however, is the FPS allowed by revolvers. Revolvers, due to the gap between the cylinder and breech face that allows gas to escape and be wasted, demonstrate a three percent to eight percent loss of velocity compared to a fixed breech barrel of the same make. The type of powder, whether quick burning or slow burning, accounts for most of the (three to eight percent) variance. For example, a 6-inch test barrel using Hercules 2400 powder produced an average velocity of 1147 fps, compared to 1080 fps produced by the same load out of a revolver of the same barrel length. Combine this loss of velocity with the weight of the gun (see table above), and velocities drop further.

The Conclusion
Fixed breach guns maximize their bullet's velocity potential, followed by semi-autos that only allow negligible decreases in potential velocity, followed by revolvers that display three to eight percent loss in velocity, due mainly to the cylinder gap.

 

Latest

Oklahoma Department Of Wildlife Conservation Logo
Oklahoma Department Of Wildlife Conservation Logo

Oklahoma Wildlife Commission Passes Rules for Nonresident Hunters, Public Hunting Lands

New emergency rules and resolutions for public hunting lands were approved last month by the Oklahoma Wildlife Conservation Commission.

First Look: Premium and Premium Deluxe Die Sets From Redding Reloading Equipment

Redding Reloading Equipment has expanded its Premium Die Set and Premium Deluxe Die Set product lines, including over seventy of the most popular cartridges in the industry today.

Junior Hunter Gear: Get Your Kids Into the Field

Looking for ways to get your fields out from behind the screens and into the great outdoors this summer? Check out these great pieces of outdoor kit to help spur the process.

Stealth Cam Adds On-Demand Livestream

Shortly after teasing the launch of its new trail camera functionality at the 2025 SHOT Show, Stealth Cam has announced that On Demand Live Stream is available via the Command Pro app.

#SundayGunday: Benelli Super Black Eagle 3 A.I.

On this week's #SundayGunday, Digital Associate Editor David Herman talks with Benelli Vice President Tim Joseph about Benelli's new Super Black Eagle 3 with A.I. barrel technology.

NRA Foundation Awards $13,500 in College Scholarships

The National Rifle Association is proud to announce the Grand Scholarship winners from the 2024 Youth Education Summit (Y.E.S.)—a group of exceptional students selected for their leadership, initiative, and dedication to advancing NRA programs within their communities.

Interests



Get the best of American Hunter delivered to your inbox.