Alliant Tech Systems’ GPS-guided Precision Guidance Kit hopes to do for artillery shells what Boeing’s JDAM tail kit has done for conventional bombs – or what ATK’s APMI kit has done for 120mm mortars.
The Western way of war has largely pushed conventional artillery off of the battlefield. A 200 – 300 meter CEP (Circular Error Probable, where 50% of rounds hit within that radius) just isn’t viable when you need to reduce the risks of friendly casualties and collateral damage. Attempts to improve that performance began in the 1980s, but ran into 2 big roadblocks: cost, and reliability.
GPS guidance and new technologies like MEMS have helped solve the reliability problem, and Raytheon’s widely-fielded M982 Excalibur rounds offer a publicly-disclosed CEP of 20m. It’s probably a bit less in practice. On the other hand, they cost over $100,000 per shell, and must be produced as a complete unit. Enter artillery fuze and propellant maker ATK’s XM1156 Precision Guidance kit, which screws into existing 155mm M549A1 and M795 shells, costs less, and offers < 50m CEP. That's good enough to make PGK an important supplement, and the US Army is pursuing it.