Here's some morningstar data for the two funds:
VBIRX, 2.98% SEC yield, x2.66 duration, 2.90 year maturity
BCOIX, 3.66% SEC yield, x5.80 duration, 7.95 year maturity
So let's apply a 0.25% increase in bond yields across all bonds, and see what happens:
0.25 x -1 x 2.9 = VBIRX loses -0.73%
0.25 x -1 x 5.8 = BCOIX loses -1.45%
2.98% - 0.73% = 2.25% interest minus loss of capital (VBIRX)
3.66% - 1.45% = 2.21% interest minus loss of capital (BCOIX)
If interest rates go up, and bond yields follow, BCOIX will trail the returns of VBIRX. When there isn't a rising yield envinment, BCOIX will beat VBIRX.