cross correlation between two different sections of two vectors.

Given two vectors A and B of equal length.

first i determined the value of the lag at which the cross correlation between A(1:100) and B(1:100) can be maximum in the ff way.

[r, lags]=xcorr(A(1:100),B(1:100))

[r_max,idx]=max(r)

lag_max=lags(idx)

is there any possibility that the value of lag_max to be different when we do the same for A(1:200) and B(1:200)? I get a little bit different value in my case, but I can't figure out the physical resean.