Curious about barrel temperature tolerances

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somanyquestions

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This will be my first post here, and i truly how I'm not asking a stupid question or one that's already been asked a thousand times (I couldn't find anything with multiple searches but hey).

I am curious, what is the temperature threshold at which rifle barrels are ruined? I've seen people shoot to cherry red and then pick it up after it's cooled and shoot again like it's nothing, and i know when gunsmith sporterize old milsurps they use a torch on the sight blocks to desolder them.

On the opposite end of the spectrum, Demo Ranch showed a campfire ruin the temper of ar500 plates so projectiles they would normally stop punched right through.

So what's the threshold for barrel murder? Is the steel that much of a different composition from ar500? How do you know if you are going to ruin a barrel?
 
If you get it red hot it’s ruined in my view. Most carbon or low alloy steels dont get their heat treat condition messed with below 700F. If its glowing it is way above that. They do get weaker though long before that point. If the hand guard is too hot to touch then stop.
 
700F is the mark then? That's about 360 C iirc? What is the desoldering point? And you say it gets weaker before that, about when does it start permanently (without a complete retempering) softening the metal?
 
Yes it starts getting temporarily weaker at 200F or so so wear could increase. Not a lot but a little.

Barrels are often 4140 or similar which get tempered starting upwards of 700. So above that you could get into permanent strength loss
 
Unless the barrel is chromed lined, shooting a barrel that hot accelerates the throat erosion that takes place. For a blasting, spray and pray, it probably dose not matter. For a high accurate bench gun your shortening the life of the barrel.

Good rule of thumb if it's too hot to touch, allow it to cool. Most all guns start loosing accuracy as they heat up past a certain point.
 
I've always done just that. My grandpa taught me early on that I shouldn't shoot a hot barrel. I use the cool down time to check my targets, do some math, repaint any gongs, etc. Mostly this question was because I have never heard of anyone retempering a barrel after stuff like (mentioned above) desoldering the front and rear sight blocks.
 
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