Load testing (grouping) with heat

Hey guys, I just got back from the range with my father-in-law and I've got a little bet going and I need some wisdom.

-Father-in-law shoots groups with a HOT barrel.

-I tell him he should wait for the barrel to cool between shots to get a better sense of the groupings. (This is what I've read but I've never tested the opposite)

-He says it doesn't matter because a hot barrel will only change POI and not impact the actual groups.

(In his defense, he was shooting really tight groups with a piping hot barrel. But I think those groups might be different if the barrel had a chance to cool between shots)

Also, hes shooting a bull barrel .308. Not sure if that matters at all...

What are your thoughts?

I have to go with your FIL. I've even thought of bringing my IR temp gun and shoot the chamber to find what, if any particular temp shoots best. I find a warm barrel, shot at sufficient intervals that maintain any even temp yields my best groups.

Thanks Texas! I know it shot well when it was hot but will the POI, or spread, change if the barrel is allowed to cool between shots? Or will the groups not change? As long as the shooter does their part.

Depends on the barrel, most of time the group will open up with heat. As the barrel heats up things change, metal expands, the barrel will accually get longer, not much but it will. Also any stress in the steal with the manufacturing process will start showing up.

I too agree with your FIL. All my rigs are close to 1" barrel thickness (bull) . I'll shoot all of them all of them at warmer temps especially at long distance

In my (albeit limited) experience, yes the poi will change, but the groups may remain the same. How much it will change depends upon a lot of factors as Eddies and JB say. I noticed a big improvement in my model 12 BVSS once I bedded the action. Large POI movements associated with barrel temp changes became much smaller movements, for all the reasons stated above, and more.

The added heat will ruin the barrel quicker. In f-class it isn't an option to time your shots. I don't know any benchrest shooter that shoots his barrel sizzling hot. Heat causes fire cracking which will end up killing the accuracy.

Thanks guysß