A worn sear or rear bolt will make the gun 'rapid fire' like a machine gun, but too fast to work properly. The gun may not stay cocked either. These are both caused by the rear bolt slipping off of the sear that is supposed to catch it and keep it back in the cocked position. If either your sear or rear bolt is worn, Tippmann suggests replacing both at the same time. A worn sear will wear down a rear bolt faster than norma and vice versa. Replacing only 1 of them may result in having to replace the same part again a lot sooner. This is the 'old ' style sear. New 98 Customs are coming with the A5/Cpro sear and spring. The receiver body internal milling has changed. At this time we do not know what the serial number was when this change was made for the 98 Custom's. If your sear is a pull sear(98-35), it will have a tab on the end to hook onto the sear spring.