I'm asking my suppressor to perform for me on various guns during a given range session, its a .308 cal and as an example I will shoot it on the 6.5 Grendel for 40 - 50 rounds and then move it to a .270 for the same and by the time I finish I put it on my 308.

After 100 rounds of slow/moderate shooting (load development) the suppressor is very warm perhaps hot. A light mirage will be visible through the 308 scope even though the barrel is about to send out the cold bore shot.

Anyhow - seems that groups open up for me on the 308 when it is last in line on the range, being the bullet doesn't contact the suppressor I'm not convinced that a hot can is effecting my POI - it could just be shooter fatigue as I am not only laying rounds downrange but also swapping gun setups, loading mags, swapping scopes, etc...

What do you think does a hot can effect Point of Impact on a cold barrel?

Shooter fatigue would be my first guess. As you said, since the bullet doesn't contact the suppressor, I wouldn't think there's much interaction there.

QD or direct thread? If direct thread, you could argue that while you're screwing it on and getting everything ready, the hot suppressor begins to transfer heat right at the end of the barrel. Depending on the weight of the .308 barrel, I suppose there is a small chance that heat transfer is causing a shift?

20/20, but what happens if you let it cool for 15-20 minutes, then transfer it and shoot it?

It’s a direct thread

I suppose a variable is removed if I let it cool but I’m usually pressed for time at the range and don’t have that option hence the question.

It’s not a significant variance but when load developing perhaps I’m skewing the results by not letting it cool off...