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Test Bolts: What they are and their use.

7K views 8 replies 6 participants last post by  fatso14 
#1 · (Edited)
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.
 
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#3 ·
Part II

So is having a Test Bolt necessary to work on an M1903 or A3 rifle, an M1 Garand or M14 rifle? No, it isn't. It will come in handy often enough if you work on these rifles enough that the cost of getting one is justified, though. You don't need one if you are assembling a couple of rifles, but if you plan on working on them a lot, a Test Bolt will come in handy.

Test Bolts are the most handy for M1903/A3 and M1 Garand rifles as there was a large variation in the bolts over the years and the barrel chambers were not chrome lined. This is especially true with M1 Garands.

Test Bolts were not as necessary with G.I. M14 receivers, barrels and bolts because they were made to a higher standard of precision than the other two rifles. HOWEVER, NO civilian Semi Auto receiver is made to the same precision standard as G.I. M14 receivers were made. Some civilian receivers are closer to G.I. spec than others, but no one yet is making a civilian receiver exactly to G.I. standards. That would cost too much for commercial economics. So an M14 Test Bolt is actually more handy to have when working on Civilian Semi Auto M14 receivers than when working on G.I. M14 receivers or rifles.

The next question is can you use a Test Bolt in place of a regular issue bolt? Well, you can't do it with an M1903/A3 Test Bolt because the handle is different and won't work. No Government Maintenance Facility would ever have used a Test Bolt to replace a standard bolt in an M1 Garand or M14, because a Gage costs one heck of a lot more than a standard bolt. Do the rest of the parts that go in a standard bolt fit in a Test Bolt for the Garand and M14? The answer is yes. So SHOULD you use a Test Bolt if you don't have a standard bolt and you want to complete a rifle? Ah, there's the rub.

I've actually seen a few Garands and at least one Civilian M14 receiver with Test Bolts in them and all the rest of the parts to make a complete bolt assembly. They were always assembled and placed in a rifle by someone who did not know what they were doing and in most cases did not know what a Test Bolt was and the proper use for one. The answer to the question of SHOULD you use a test bolt, even as a last resort, is a resounding NO YOU SHOULD NOT. If you look at the front of the Test Bolt, directly at the bolt face, and compare it to a standard bolt - you will see where they took an End Mill Cut across the face of the bolt to make it so precisely to G.I. specs. That means the partial ring of steel that keeps the bolt inside the end of the chamber and supporting the cartridge case has been severely weakened by being cut away. That can allow a weak cartridge case to possibly expand too much and possibly rupture during recoil. You do NOT want even the possiblity of that happening, so DON'T use a Test Bolt as a replacement for a standard bolt in a gun you are going to fire.

OK, so what happens if you have an extra Test Bolt you don't need? What do you do with it? I would suggest you sell or trade it to someone who will use it for the intended purpose. They are worth more than a standard G.I. bolt, even at today's inflated prices for a G.I. bolt. Even if you can't get full value for one, you may be able to trade for a replacement standard bolt or close to what a G.I. bolt is selling for. Just PLEASE don't use a Test Bolt in a standard rifle that is going to be fired due to safety concerns.
 
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