High shot volume, hot barrel, and accuracy question

[roymunson]

I'm admittedly pretty new and pretty self taught when it comes to the nuance of reloading and rifle accuracy.

I was shooting my 300 WSM (180 gr TTSX, 65 gr H4350) and generally it's been an accurate enough round that I'm pleased with what it'll do in the field.

Today I wanted to shoot. Ambient temp was around 80-85 degrees, and I shot quite a bit. Barrel was hot to the touch to the point I couldn't maintain contact with my hand on the barrel.

The impacts started running. Not incredibly, but 2-3 MOA. Which is enough to get my attention out of an otherwise MOA or just sub MOA gun/round.



I hope I didn't ruin anything, but if I did, it was out of ignorance, so please don't flame me. But 10+ rounds in 10 minutes was definitely causing groups to change and spread out. I want to blame the hot weather/hot barrel rather than my reloads and other factors because of how well it's shot previously.

Can someone please educate me on the effects of a hot barrel to accuracy.

 

[Formidilosus]

I'm admittedly pretty new and pretty self taught when it comes to the nuance of reloading and rifle accuracy.

I was shooting my 300 WSM (180 gr TTSX, 65 gr H4350) and generally it's been an accurate enough round that I'm pleased with what it'll do in the field.

Today I wanted to shoot. Ambient temp was around 80-85 degrees, and I shot quite a bit. Barrel was hot to the touch to the point I couldn't maintain contact with my hand on the barrel.

The impacts started running. Not incredibly, but 2-3 MOA. Which is enough to get my attention out of an otherwise MOA or just sub MOA gun/round.



I hope I didn't ruin anything, but if I did, it was out of ignorance, so please don't flame me. But 10+ rounds in 10 minutes was definitely causing groups to change and spread out. I want to blame the hot weather/hot barrel rather than my reloads and other factors because of how well it's shot previously.

Can someone please educate me on the effects of a hot barrel to accuracy.

In a properly stress relived barrel and a properly assembled rifle, the barrel temp does not materially effect mechanical precision. It does cause barrel mirage, which causes issues that most people incorrectly attribute to “thin barrels don’t shoot when hot” myth.

You didn’t hurt your barrel. If you want to shoot the rifle when it’s hot and not spend an hour getting 10 rounds off, a barrel mirage shield works.

 

[roymunson]

by mirage are you saying the "heat waves" coming off the barrel obstructing sight, or are you saying my aimpoint is impacted similar to light refraction in water kinda concept?

 

[Formidilosus]

by mirage are you saying the "heat waves" coming off the barrel obstructing sight, or are you saying my aimpoint is impacted similar to light refraction in water kinda concept?

Those are kinda the same thing in this case. The mirage changes the apparent position of the target when crowing through the scope, usually resulting in vertical spread of groups.