page_title: .40 S&W
section_title: Case failure reports
hierarchical_section_title: .40 S&W / Case failure reports
caption_attribution_description: A .40 S&amp;W Beretta 96 barrel breech photograph showing case support for the cartridge at the feed-ramp. The gun has about 4,000 rounds total through it and 150 Winchester Ranger 155gr JHPs since last cleaned. This case was taken from one of those fired bullets. As can be seen, there is a small 1/16th inch area unsupported at the feed ramp. Internally this Winchester, a CBC and a Speer case I examined, all had a cupped/concave web area to move the combustion area forward of the small unsupported area at the feed ramp. No case bulging was found on any case fired in this weapon. If you have reason to suspect your weapon does not fully support the case at the feed ramp, disassemble it and perform this check.
context_page_description: The .40 S&W is a rimless pistol cartridge developed jointly by major American firearms manufacturers Smith & Wesson and Winchester. The .40 S&W was developed from the ground up as a law enforcement cartridge designed to duplicate performance of the Federal Bureau of Investigation's reduced-velocity 10mm Auto cartridge which could be retrofitted into medium-frame semi-automatic handguns. It uses 0.40-inch diameter bullets ranging in weight from 105 to 200 grains.
context_section_description: The .40 S&W has been noted in a number of cartridge case failures, particularly in older Glock pistols due to the relatively large area of unsupported case head in those barrels, given its high working pressure. The feed ramp on the Glock .40 S&W pistols is larger than on other Glocks, which leaves the rear bottom of the case unsupported, and it is in this unsupported area that the cases fail. Most, but not all, of the failures have occurred with reloaded or remanufactured ammunition. Cartridges loaded at or above the SAAMI pressure, or slightly oversized cases which fire slightly out of battery are often considered to be the cause of these failures, which are commonly referred to as "kaBooms" or "kB!" for short. While these case failures do not often injure the person holding the pistol, the venting of high pressure gas tends to eject the magazine out of the magazine well in a spectacular fashion, and usually destroys the pistol. In some cases, the barrel will also fail, blowing the top of the chamber off.
caption: Beretta 96 Feed Ramp
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