AR bolt strength/ stability?????

syncro

syncro

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If a fully assembled AR bolt is subjected to very high temperatures ( lets say vehicle fire) is it still safe to use??? The bolt looks fine and after a thorough cleaning/ lubrication it seems to function well. I do not however want to test the bolth with a loaded firearm. Besides taking to a gun smith, are there any sure fire ways to determine if the bolt is safe???

Thank you
 
all depends on how high did the temperature reach and how fast it was cooled down, but if you feel the need to question it, I wouldn't use it.
 
Check it for any cracks (even hairline), check it for fit, if you have snapcaps run those through it, and if you still decide to run it in your gun... I would suggest firing one round then check it again... Fire maybe 5 rounds, check it... Then 10... 25... 50... 100...

The biggest thing to watch out for when you start to fire it is cracks.


That being said, as USP said, they are only $50-75...
 
The original tempering temperature on an AR bolt can't be much over 400 degrees C. I would say that chances are excellent that it attained temperatures higher than that in the fire and is now softer than it was ever intended to be.
 
There will be no safe or practical way for you to determine the integrity of a bolt that has been in a fire. You might be fine or you might lose a body part, it's not worth it!

Was the entire gun in a car fire or just the bolt/bolt carrier assembly??

If the entire gun was in the fire, there are parts, other than the bolt, which could have been compromised (barrel, barrel extension, fire control group) and could cause serious injury/death.
 
Even if the hardness is where it should be, after being exposed to high heat if not properly stress relieved it can be quite brittle and potentially shatter.
 
you gentlemen have been a huge help, thank you. Now, another question. Is a military bolt higher grade than that of a civilian manufactured one? As for the guy that told me i can test it but do not have the experience to do so, i bet you feel cool.

Thanks again guys
 
Before you get all snarky, the guy who said it wasn't practical at your level was referring to the fact that you probably don't have the necessary equipment sitting in your garage to test the hardness and MP test the bolt. Add to that, the cost to get it tested would likely exceed the cost of buying a new one. :)
 
Was your car air cooled or did it get get hosed down with water? If it was air cooled the bolt should be fine. (If it was made in china? It was a POS anyways.) 900c to 1200c is the average gas fire. Carbon steel average melting point is about 1425 to 1540c. The upper transformation range is about 1330 for carbon steel. hit it with a punch to see if it dents easy....so its OK.
let your wife cycle some rounds first to be on the safe side. HO ho Hooooo
:D:onCrack:
 
KevinB works for Knights Armament, with their Military / Government group.
See his signature block.

He is Ex-CF, and does not forget about us up here.

Maybe next time you ask for help, and get some from a knowledgable invidvidual, you should not bite the hand that feeds you.
 
Dude relax,

My point was that unless you have access to whatever the thing is called that allows for surface hardness testing (we have some but while I know how to use it I have no idea what its called) as well as a test barrel, high pressure testing and the ability to magnaflux the part after to test for cracking and then its not worth the unk factor.

Milspec for bolt steel is Carpenter 158 steel (shot peened etc.) however the VAST majority of commcercial bolts on the market are not, and are 8620.

I am not a metallurgist, but I do work with some pretty smart engineers, and have been learning a thing or to about the effect of heat on materials.

But I would recommend doing some reading...

http://www.interlloy.com.au/data_sheets/case_hardening_steels/8620.html

Just saying ;)
 
I say don't be a Pu55y. Pay up your dismemberment/death by stupidity insurance and have at it. What's the worse that could happen? Look at the bright side, your house could be paid for, and the next guy to move in with your wife wouldn't have to worry about a mortgage. :slap:

Yes get rid of that bolt. Buy a new one. :D
 
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