Non lead bullets question

[KSB209]

Have to use non lead here in CA. At what velocity do I have to worry about them not preforming and opening up? Mainly shooting the Barnes TSX and Hornady GMX. I'm not shooting much past 300 yards now but practicing for 2021 elk and deer season.
I want to be proficient up to 500 yards. My hunting rifles are 270, 308, and 300 WM.
At 400 yards the 308 and 270 will probably be sub 2000 FPS the 300 WM will be around 2200 FPS based on ballistics from federal and hornady websites.
So at what speeds make the copper and GMX not "expand"? Or am I just over thinking this issue?

 

[JMW67]

1800 fps is a good number to go by

 

[KSB209]

Thanks. I figured 2000 FPS was nearing the threshold but didn't know for sure. I would assume a tipped bullet similar to Barnes TTSX might open up a little better at lower velocities a little better. Would you say that is a fair assumption?

 

[Stammster]

In your 270, start a 129gr LRX out around 3100-3200 fps, and you'll be > 2000 fps at 600 yds.