Accurate Arms Warning

This warning is from the Accurate Arms 2002 load guide.  This is the text of the warning in full:

SPECIAL WARNINGS !!!

Concerning the internal dimensions and configurations of centerfire metallic calibers, especially semi-auto pistols. 

This warning is not aimed at specific weapons, but any weapon with the conditions or dimensions as described below.  Accurate Arms did not compile special data for any weapon.

Chamber dimensions:

It is extremely important to note that due to aftermarket modifications and for certain factory produced semi-auto pistols, some pistols have chamber configurations that do not fully support the chambered cartridge case. 

This modification is incorporated to aid in the reliable feeding of the round from the magazine.  Although this practice is acceptable with some calibers such as the 45 ACP which generate relatively low pressures, this kind of incomplete support can be a real problem with high performance calibers such as the 9mm x 19P, 38 Super, 40 S&W, and 10 MM Auto calibers.  Although it might also be acceptable for first fired conditions such as factory ammunition or new unused cases, a potential hazardous condition can be created when cases are reloaded for the second or subsequent time.  Whenever a deformed case results after firing (eg. a bulged or "pregnant" shape from the base of the main body towards one third to half of the case body), it 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 will then cause the case to fail and the gasses to be ejected into the internal cavity of the weapon.

The loading data published by Accurate Arms was developed in our ballistic laboratory in accordance with SAAMI test methods and equipment and does not exceed Maximum Average Pressure recommended by SAAMI.  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 with may result in destruction / damage to the firearm and / or injury or death to the shooter and / or bystanders.  This can happen no matter who's propellant is used.

We recommend that if you own a firearm where the chamber does not fully support the chambered round and is producing the above mentioned symptoms, you contact the manufacturer to determine if the case is fully supported, or have a competent gunsmith examine the firearm and determine the amount of support provided the case.

If your firearm does not provide complete support for the case, please take extreme care and refrain from reloading cases.