There have been many variations of "improved" cartridges over the years, and even several different flavors within the "Ackley" cartridges. The 280 is certainly no exception. When the 280 Ackley Improved was developed and standardized through the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) by Nosler®, the decision was made to honor Mr. Ackley's original design intent by headspacing the cartridge such that standard 280 Remington ammunition would chamber with slight (.003"/.004") crush at the shoulder/neck intersection and fire form into the Ackley chamber without the need to seat the bullet into the rifling. In fact, Mr. Ackley headspaced his "improved" cartridges by simply grinding a standard "go" headspace gage for the parent cartridge back by 0.004" and using it to headspace the new version. This is also the way that many large custom gun shops have chambered the 280 Ackley for almost 40 years. In order to achieve this, any standard 280 Remington firearm being opened up to the Ackley must have the barrel set back one turn prior to reaming the chamber – simply improving the standard chamber without doing so will yield excessive headspace, even though this was common practice for many gun makers over the years as well. Based on this design, the 280 Ackley Improved was accepted by SAAMI in February of 2008 and has enjoyed tremendous success ever since.
Occasionally, a rifle that was "improved" by simply reaming the chamber without first setting the barrel back will turn up and result in questions about its compatibility with factory ammunition. Unbeknownst to their owner, most of these guns have headspace dimensions of between 0.010" and 0.015" greater than the SAAMI version of the 280 Ackley Improved. These rifles are perfectly functional so long as they are used with ammunition that has been properly formed and sized to fit their chambers. If the customer wishes to use their rifle with modern SAAMI-compliant 280 Ackley ammunition, it must be re-headspaced to properly chamber the ammunition.
