π Is 3 In GURPS

In GURPS an M1911 firing caliber .45, ball, M1911 does 2d pi+

That's mil-spec ammo doing approximately 885 fps 25'6" from the muzzle.

185gr Golden Sabre JHP by Remington flinging along at 1015 fps at the muzzle does...

2d(0.5) pi++... differing from ball only because it's a hollow-point.

The same sort of thing happens with 9x19mm too.  115gr ball and 124 gr ball end up being the same.

Heavier rounds going slower and lighter rounds going faster end up within a point of one another and often so close the the original round's damage numbers that it's a wash.

Judging from Lucky Gunner's neat little charts it's a fair simulation of "reality" for game purposes.  It at least follows some expectations from the real world in parallel so the players won't complain too loud about it.

The lack of expansion in some of those rounds is even accounted for in the game rules, with GM having to make the call about whether a round is sufficiently advanced to skip the expansion check.

With our above example, and Lucky Gunner's chart, we can make an argument that it does expand reliably enough to avoid the roll.