This page was first published online 1-1-2007

This page was last updated 1-1-2007

Feed Ramp Designs

The conventional feed ramp in a 1911 pistol has two components. The feed ramp in the frame and the feed ramp in the barrel. See Figure 1. During normal cycling, when the slide moves forward to strip a round from the magazine, the nose of the bullet first engages the feed ramp in the frame, which directs the front of the cartridge upward toward the chamber. As the round moves forward and up, it engages the barrel's feed ramp and eventually is pushed into the chamber. Ramped barrels have an integral feed ramp that replaces the frame feed ramp. Figure 1 shows this design in a 1911 pistol.

Figure 1

Supported vs Unsupported Barrel Chambers

The barrel's chamber provides support for the cartridge case. Conventional barrels in 1911s have a shallow concave cut in the lower rear of the chamber that is part of the feed ramp (labeled "Barrel Feed Ramp" in the left photograph in Figure 1). This cut exposes a significant portion of the cartridge case (the left photograph in Figure 2). This type of chamber is called an unsupported chamber because it does not offer support for the full length of the case. A supported chamber offers much more case support, as shown in photograph on the right side of Figure 2. (Note that the cartridge cases in Figure 2 have been placed at a rearward position, similar to how they would be in the gun during firing when the case is pushed backward to the breech face. This more accurately demonstrates the amount of the case that is supported/unsupported by the chamber when the gun fires.) The blue arrows point to the unsupported region of the case, which is also marked with a black line. The black line on the cartridge case in the unsupported barrel is much longer than the line on the supported case. The exposed region of the 38 Super case in the conventional (unsupported) chamber is generally strong enough to handle normal pressures without bulging. But if pressure becomes too high, the case in this exposed region will swell and can burst with extreme pressures, which can result in damage to the gun and injury to the shooter and bystanders.

Figure 2

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