It really isn't all too difficult to stop copper slugs if you start using them on bigger game. Heck, even a rather puny sub-200 pound caribou is capable:

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This 120 7mm TSX didn't expand a whole lot in the process either. (I've killed quite a few caribou with the older 140 XFB with no bullet recoveries and much quicker killing effect than what this faster slug managed.) Bigger game are great receptacles for bullet recovery IME, even the copper slugs. No sense is using less than the 210 since it shoots well and has the cavity advantage of the TTSX.

Sometimes, the air you 'let in'matters less than the air you 'let out'.