M-16 Bolts Not Interchangeable? Any Truth To This?

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From my first day of BRM ,till the day I ETS'd 14 years later I was told by EVERY armourer I met & All the training NCOs that our M-16 were all essentially custom made and that the bolts for each of the were made for that rifle and would not work in another M-16.

After I got off active duty I went to work as a machinist & got a chance to see first hand how mass production manufacturing actually works, & I know damn good & well that those bolts are run by the hundreds ,THEN assembled , THEN assembled into an upper reciever. And that as such they are TOTALLY interchangeable.

Has anyone else been told this? Does anyone have an idea WHY such a rumor would be started?
 
The story was probably started because they didn't want people messing around with their rifles. The headspace should be checked on every one built and if you start swapping bolts and carriers you could eventually find an unsafe combination.

That is just my ignorant opinion.
 
I think BITMAP has it right. If you go through enough bolts, eventually you will probably find one that won't headspace. That's why it is a good idea to have a GO/NO GO guage.
 
What we were told in basic was that it was due to wear. Nothing we got was new, that's for sure, and the story was, the bolt/chamber/receiver all had wear, and they all aquired that wear together. So bolt A, Chamber A, receiver A all fit each other perfect, but bolt B and receiver A, while not entirely incompatible, didn't fit quite 'right'.

Kind of like a glove, or a good pair of shoes. After a while, they fit you properly, but anybody else with them on isn't going to think they're all that great.
 
Swapping bolts is not recommended because it may cause uneven wear on the bolt lugs. This can lead to uneven strain on the lugs and premature failure.
 
I just bought a bolt assembly from local store, It looks just like the one I had in my assinged M16A2 while in the ARMY.

My colt bolt is different only at the back bottom half is Machined off.
 
Sounds like you are talking about the bolt carrier, not the bolt.
Colt uses M-16 carriers, and used to grind of the lower rear to prevent them being used with an auto-sear or M-16 full-auto parts.

I agree that the bolt should stay with the rifle it started out in.

They are matched up & headspaced with a barrel extension at the factory, and wear patterns will make a differance eventually.

If a new bolt is swapped out and used with an old barrel extension, the headspace should definately be checked.

rcmodel
 
I can understand why armourers say this because somebody is going to take a notion to swapping parts out and sooner or later you are going to have a problem. Uneven locking lug wear isn't an issue. Honestly, I can't imagine where you would have heard that one in the first place.:scrutiny: However, headspace may be an issue. When I teach an M-16 or M-4 class, I figure they are adults so I tell my classes the truth.
"If you swap around bolts, there is a chance you may wind up with excessive headspace. Now of all the bolts and barrels I've replaced over the years, I have yet to run into one that didn't headspace correctly no matter if both were new components, an old and new mix or a couple old parts thrown together. However, in EVERY case, I make it a habit to recheck the headspace. We have the guages to check for this condition. You do not. If the headspace is excessive because you were swapping bolts with your buddies, you have 52,000 PSI chamber pressure that is going to come back in your face because you tuned out what I've just told you. You've been warned."
 
You should not trade used bolts with out checking headspace.

New bolts in a new barrel with a new extension that is properly headspaced, you can move the bolt around. I have taken over a dozen complete uppers from a wide variety of manufacturers and moved the bolts all around checking headspace and it was always correct.

As far as the Army its all weapon systems, M16, M60, M249, M240
 
I allways wondered about this as well. I have heard from almost everyone that manufacturing tolerances allow for interchangability....however, if you get a bolt that is on one end of the tolerance range & a barrel extension on the other end, it seems that could potentially be problematic. A GO/NO GO set of guages only costs around $40, so that is what I will do. As stated earlier, I do not want to take a chance with 50K+ of pressure around my face!:what:
 
See, that's the thing I hate about stupid BS stories like this. Next thing you know that sort of information is being passed around like it's the Gospel because "somebody with the training told me so" and bang, another urban legend is born. :barf: Next time somebody tells you that it''s a custom-made part or causes uneven wear on locking lugs or something crazy like that, tell them to bring you their TM or TO (every shop is going to have one so don't let them BS you that they don't) and insist they show you were they are getting that information from. As they say, "cite your source."
Now as one instructor to another, if you are CATM, 2111, a PMI or what not, how about giving your students some credit. Yes, they aren't the brightest bulbs on the tree but they are adults. Just be honest with them and let them know the facts up front that while it might not be a problem, it would seriously suck to be you if you get the one that's not going to follow the rules and explode in your face. I have a lot more respect for people that will deal with me honestly than some idiot that wants me to believe that M-16s are assembled by super-secret squirrel craftsmen using a top secret magical pixie dust to fit the parts. :rolleyes:
 
I like the shoe analogy.

Headspace is set at the bbl extension. You dont have to check it if you get a new bolt for an old AR. Not a bad idea, but if your AR15 goes down while the S is HTF, surviving to check the headspace should be your first priority, so get your spare bolt or (complete BCG) in and worry about the headspace later.
 
I just checked my smart book(which I kept for whatever reason), and it says "Warning, do not interchange bolts between rifles." That's it, nothing more.

So I suppose I got that bit from my Drill Sergeants, cause I certainly didn't get it from my book!
 
When I was working as unit armorer in the mid 70's, the Army sent out a tech bulletin telling every one not to switch bolts on M16's.

The premise was, as stated above, that they would wear at different rates and eventually cause an unsafe situation.

Granted, this was a long time ago, but I can attest that it was an official policy at one time.

PS: We read it, announced and then forgot about it.
 
Also in the early 70s (Army)we had to electropencil the serial# of the rifle on the bolt carrier to make sure no parts were swapped. Armorer had to verify they matched before allowing them back in the arms room. They were stored seperately.
 
Uneven locking lug wear isn't an issue. Honestly, I can't imagine where you would have heard that one in the first place.
Click to expand...

How about the instructor that certified me as an armorer on the M-16/AR-15 type weapons.

It's not a wives tale, it's a reported issue that the Army, and many of the AR manufacturers warn you about. Once a bolt has been worn into a particular barrel extensions it shouldn't be swapped into about other barrel.

It's really not a big deal how often do you go about switching bolts?
 
I was a small arms repairman from 72 to 76. The book stated that if bolts were changed that had to be checked with a head space gage. We had go and no go gages. If it passed both, it went back to the unit.
 
The AR-15/M16 bolts wear along with the receivers of the guns they're in. If you take out the bolt in one weapon and exchange it with another, they won't match up. The rifle will still function, but headspace should be checked for safety.
 
When swapping bolts one should always test the bolt with at least a Field gage.
This is the longest acceptable headspace that will still allow the weapon to safely function.

If you want to obtain the best possible accuracy from your AR15/M16 then you should trial fit bolts until a minimum Go headspace gaging is obtained.

Go ahead and swap bolts without checking headspace if you are foolish or care free.
It is a 50,000 pound per square inch explosion going off next to your face, not mine,,,,,,,,
 
I just bought a bolt assembly from local store, It looks just like the one I had in my assinged M16A2 while in the ARMY.

My colt bolt is different only at the back bottom half is Machined off.
Click to expand...
That's because the heavier one is an M16 carrier and the Colt is a AR-15 carrier. I only use bolts headspaced to the barrel and M16 carriers. Why? Cause that's how Noveske sends them to me.:D
 
Quote:
Uneven locking lug wear isn't an issue. Honestly, I can't imagine where you would have heard that one in the first place.

How about the instructor that certified me as an armorer on the M-16/AR-15 type weapons.

It's not a wives tale, it's a reported issue that the Army, and many of the AR manufacturers warn you about. Once a bolt has been worn into a particular barrel extensions it shouldn't be swapped into about other barrel.

It's really not a big deal how often do you go about switching bolts?
Click to expand...

Can you show me a TM/TO reference concerning that? :confused:
 
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