  Recent measurements of the out-of-plane magnetoresistance of delafossites
(PdCoO$_2$ and PtCoO$_2$) observed oscillations which closely resemble the
Aharanov-Bohm effect. We develop a semiclassical theory of these oscillations
and show that they are a consequence of the quasi-2D dispersion of
delafossites. We observe that the Lorentz force created by an in-plane magnetic
field makes the out-of-plane motion of electrons oscillatory, similarly to
Bloch oscillations. Analysis of the visibility of these Bloch-Lorentz
oscillations reveals the mean-free path to be $l \approx 4.4 \mu m$ in
comparison to the literature in-plane mean free path of $20 \mu m$. The
mean-free path is reduced as a consequence of the out-of-plane relaxation and
sample wall scattering. Our theory offers a way to design an experimental
geometry that is better suited for probing the phenomenon and to investigate
the out-of-plane dynamics of ballistic quasi-two-dimensional materials.
