During late 1979, there were concerns that standard 30 Carbine ammo could be chambered in the VIPER trainer and cause malfunctions or extend the range of the trainer. This led to the chamber being shortened so that normal 30 M1 ammunition could not be used and the cases were trimmed to 1.10’’ The bullets were loaded to the cannelure to give an OAL of 1.880”. A small lot was made up using 150gr. Hornady bullets with orange tips. The cases were once-fired and hand trimmed to the shorter length. There shorter cases were however not necessary and no further development was done.