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Posted: 4/12/2004 1:31:26 PM EST
Recently, I picked up a copy of the Army and Air Force M16A2 technical manual. Its dated May 1991. The book details assembly and disassembly of the rifle. The manual states repeatedly:

"DO NOT interchange bolt assemblies from one rifle to another. Doing so may result in injury to, or death of, personnel."

This is the first I've heard of this. Is there something I should know if I need to buy a new bolt assembly? Why would interchanging bolt assemblies be so dangerous?
Link Posted: 4/13/2004 4:27:38 AM EST
Because headspace can change. AT ALL TIMES when changing BOLTS, it is wise to have the headspace checked as well.
Link Posted: 4/13/2004 12:47:49 PM EST
Thanks! I've seen the headspace gauges. Can you direct me or explain to me why the space would be different between rifles of the same make and model? Also, if I buy a brand new bolt from Bushmaster, is this going to be an issue? Sorry for all the questions, I appreciate the advice!
Link Posted: 4/13/2004 3:27:50 PM EST
[Last Edit: 4/13/2004 3:29:03 PM EST by rebel_rifle]
Each barrel is individually chambered with a reamer. Headspace is measured in thousandths of an inch. Just varying it one way or another a few thousandths can make it dangerous. Whether you buy a brand new bolt from anybody, it is always prudent to check the headspace when changing bolts. Don't worry about the carrier, but check when changing bolts. More than likely it won't be an issue, but considering the money you paid for the rifle and a potential visit to the ER, don't you want to be SURE?
Link Posted: 4/13/2004 3:52:14 PM EST
[Last Edit: 4/13/2004 4:31:20 PM EST by agillig]
Alright...so if I wanted to be safe, should I just buy any entirely new bolt and bolt carrier altogether? I really don't have a good grip on this-even after checking the resources on this site, and I can spare the extra money...
Link Posted: 4/13/2004 9:54:44 PM EST
It is the bolt and barrel that make the headspacing/ The bolt carrier will have nothing to do with it. If you are concerned, get a new bolt. I always try to have an extra on hand, it can't hurt.
Link Posted: 4/14/2004 4:05:55 AM EST
Originally Posted By agillig: Alright...so if I wanted to be safe, should I just buy any entirely new bolt and bolt carrier altogether? I really don't have a good grip on this-even after checking the resources on this site, and I can spare the extra money...
View Quote
If the rifle you have came with the bolt and is factory original, don't worry about it. However, IF you buy another bolt to either keep as a spare or replace it with, have the headspace checked to be SAFE. The carrier has nothing to do with headspace and they can be interchanged without worry.
Link Posted: 4/14/2004 3:14:55 PM EST
Ok, do you know where I can take the upper to have it checked RIGHT? I'm not sure if my local gun store will do this or not...
Link Posted: 4/14/2004 4:17:40 PM EST
Just find a gunsmith with a .223 headspace gauge. It only takes a few minutes.
Link Posted: 4/15/2004 11:59:53 AM EST
Originally Posted By rebel_rifle: Just find a gunsmith with a [s].223[/s] 5.56mm headspace gauge. It only takes a few minutes.
View Quote
Or buy your own HS guages, you only need a Go and a Field.
Link Posted: 4/21/2004 9:14:55 PM EST
I'm not nessesarily recommending this but I have seen many M16 bolts interchanged without checking headspace and I've never seen a blowup or even a malfunction caused by the change. Still might not be a good idea but I don't worry about it.
Link Posted: 4/24/2004 6:05:29 AM EST
yep,I've heard former vets say that at the range after qualification during cleaning that the shooters would just toss all the bolt carrier assemblies into a tub of solvent and let them soak. When they were retrieved nobody gave any mind to putting any of them back in the rifles. There was no system in place to match bolts with each rifle. I am obsessive enough about safty and have the time so I check headspace periodically on my rifles anyway. It may not be necessary but it gives me peace of mind.
Link Posted: 4/29/2004 9:07:45 PM EST
I heard as long as your using spec parts and they are all new and not worn, "that there is no problem" is this true?

I heard that a used guns, Bolt and barrel extension will wear together. And switching bolts at that point is when you worry about Headspace issues. Is that true?
Link Posted: 5/3/2004 4:42:15 PM EST
If the parts are in good condition, switching bolts is not dangerous.

"Each barrel is individually chambered with a reamer."

True, but not headspaced to that particular bolt. The AR-15/M16 is NOT a custom fit rifle. No standard issue military rifle is.

I have swapped bolts among my rifles many times, with never a problem. I have swapped bolts and bolt carrier assemblies among my and other rifles doing troubleshooting.

Where you should be concerned is in buying parts kits made up from old, worn out M16's. If you have fresh barrels and bolts from reputable manufacturers, you will not have a headspace problem.

Overall, the headspace/kaboom problem is way, way out of sync with reality.
Link Posted: 5/9/2004 2:49:28 PM EST
I keep a couple extra Brand new bolt heads incase one fails, but I was always told not to change around used ones. so I dont and probably will never unless an Emergency . lol
Link Posted: 5/10/2004 12:28:04 PM EST
I took apart all my four of my ar's at the same time, once, and lost track of which was which. With great trepidation, I reassembled and checked the headspace of each rifle. All went well and there haven't been any KABOOMS.
Link Posted: 5/12/2004 3:05:05 AM EST
Back in the 80's when I was in high school I was on the school rifle team and we shot the M16 at the National Guard Armory. When they stored their weapons they kept the bolts locked-up seperate from the rifles. There was no markings on which bolt went to which rifle. They evidently were'nt concerned with headspacing with their weapons.
Link Posted: 5/12/2004 12:08:59 PM EST
[Last Edit: 5/12/2004 12:09:16 PM EST by Va_Dinger]
I swap bolts/carriers quite often in my rifles, depending on which one is clean. I've never had a single issue.
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