SPECIAL WARNING CONCERNING CHAMBER DIMENSIONS OF SEMI AUTO HANDGUNS THAT DO NOT FULLY SUPPORT THE CASE.
A potentially dangerous condition can occur with certain aftermarket modifications, and also certain factory-produced semi auto pistols that have chamber configurations that do not fully support the chambered cartridge case. This modification is incorporated or done to aid in the reliable feeding of the round from the magazine. Although it might be acceptable for newly manufactured ammunition, or new unused cases, a potentially hazardous condition can be created when cases are reloaded a second time or more.
After firing a round in one of these handguns, a deformed case can result. We recommend inspecting each case for a bulged or “pregnant” shape from the base of the main body towards one third to half of the case body, which is a sure sign that the case is not fully supported. Although this bulged part is reformed during resizing, the case strength could be weakened. The problem occurs when this part of the weakened case again lines up with the modified part of the chamber. This may cause the case to fail, which allows the gases to be ejected into the internal cavity of the weapon.
The loading data published by Western Powders, Inc. was developed in our ballistic laboratory in strict accordance with SAAMI testing methods and equipment, and does not exceed the pressure specifications. This information is safe for use in firearms which provide complete support of the case. Failure to fully support the case with cartridges of such intensity may result in bulged cases, ruptured cases, separated case heads, or other consequences that may result in destruction/damage to the firearm and/or injury or death to the shooter and/or bystanders. This can happen with any powder irrespective of design and/or burn rate.
If you own a firearm in which the chamber does not fully support the chambered round and is producing the above mentioned symptoms, Western Powders, Inc. recommends that you either contact the firearm manufacturer to determine if the case is fully supported, or have a competent gunsmith examine the firearm and determine the amount of support provided to the case.
If your firearm does not provide complete support for the case, please take extreme care and refrain from reloading cases.