Part I
Just got a PM basically asking what the Test Bolt is and what it was used for. Though this is not something everyone will run into, it is something that comes up often enough I figured the answer should be done here on this forum. Perhaps we should make this a sticky on this forum?
A Test Bolt is a precision ground and certified gage. They were made from standard production bolts, early in the manufacturing process, before the bolt was finish machined, hardened and annealed to blueprint specifications. This way, the distance or length from the rear of the bolt lugs and the face of the bolt were made exactly as possible to the MAXIMUM length distance allowed by the blueprints.
The first U.S. rifle that I'm aware of they made significant quantities of Test Bolts for was the M1903 Springfield Rifle. I have one of those along with Test Bolts for the M1 Garand and M14. These gages were always used by at least the 3rd Echelon Maintenance Facilities out of the 5 Echelons of Maintenance. I am not completely sure, but I think the 03 Test Bolt was only used by 4th and 5th Echelon. If one is not familiar with the Echelons (or categories of maintenance) used by the U.S. military, I suggest you check out "US Military History Companion: Maintenance" at this link for a good explanation:
http://www.answers.com/topic/maintenance
OK, so what were/are they used for? Basically, if the bolt closes on the Field Reject Headspace Gage and thus has too much headspace to be safe - the Armorer can not quickly and accurately tell if the chamber has been cut too deep, the bolt is worn too much, the receiver is worn too much or a combination of any two and/or all problems are going on with the rifle. So you pull out the Test Bolt as that is certified as the longest bolt that is made by blueprint and you try it in the rifle with the Field Reject Headspace Gage. If the Test Bolt does not close on the Field Reject Headspace gage, you then knew the bolt was bad and ordered a replacement bolt. If the Test Bolt closes on the Field Reject Headspace gage, you know it is the barrel or receiver (or both) is worn out or the headspace was cut too deep. At that point, the rifle was evaced to at least a 4th Echelon shop for rebarreling and if that didn't take care of the headspace problem, the rifle was sent to 5th Echelon Depot repair for replacement of the receiver or stripped for parts and the receiver destroyed. IOW, the Test Bolt would tell you if the cheapest part (the bolt) would fix the problem or if a more expensive part like the barrel or receiver (or both) had to be replaced.
OK, so that's how G.I. Amorers used Test Bolts, so the next question is are they necessary or at least practical for use by Civilian Armorers or Gunsmiths? That will be the subject of Part II.
Just got a PM basically asking what the Test Bolt is and what it was used for. Though this is not something everyone will run into, it is something that comes up often enough I figured the answer should be done here on this forum. Perhaps we should make this a sticky on this forum?
A Test Bolt is a precision ground and certified gage. They were made from standard production bolts, early in the manufacturing process, before the bolt was finish machined, hardened and annealed to blueprint specifications. This way, the distance or length from the rear of the bolt lugs and the face of the bolt were made exactly as possible to the MAXIMUM length distance allowed by the blueprints.
The first U.S. rifle that I'm aware of they made significant quantities of Test Bolts for was the M1903 Springfield Rifle. I have one of those along with Test Bolts for the M1 Garand and M14. These gages were always used by at least the 3rd Echelon Maintenance Facilities out of the 5 Echelons of Maintenance. I am not completely sure, but I think the 03 Test Bolt was only used by 4th and 5th Echelon. If one is not familiar with the Echelons (or categories of maintenance) used by the U.S. military, I suggest you check out "US Military History Companion: Maintenance" at this link for a good explanation:
http://www.answers.com/topic/maintenance
OK, so what were/are they used for? Basically, if the bolt closes on the Field Reject Headspace Gage and thus has too much headspace to be safe - the Armorer can not quickly and accurately tell if the chamber has been cut too deep, the bolt is worn too much, the receiver is worn too much or a combination of any two and/or all problems are going on with the rifle. So you pull out the Test Bolt as that is certified as the longest bolt that is made by blueprint and you try it in the rifle with the Field Reject Headspace Gage. If the Test Bolt does not close on the Field Reject Headspace gage, you then knew the bolt was bad and ordered a replacement bolt. If the Test Bolt closes on the Field Reject Headspace gage, you know it is the barrel or receiver (or both) is worn out or the headspace was cut too deep. At that point, the rifle was evaced to at least a 4th Echelon shop for rebarreling and if that didn't take care of the headspace problem, the rifle was sent to 5th Echelon Depot repair for replacement of the receiver or stripped for parts and the receiver destroyed. IOW, the Test Bolt would tell you if the cheapest part (the bolt) would fix the problem or if a more expensive part like the barrel or receiver (or both) had to be replaced.
OK, so that's how G.I. Amorers used Test Bolts, so the next question is are they necessary or at least practical for use by Civilian Armorers or Gunsmiths? That will be the subject of Part II.