Rabaul in Papua-New-Guinea is an extremely active andesitic caldera complex that displays a large spectrum of eruption styles. Since 1878, four sub-plinian VEI-4 and ten VEI1–3 (effusive, strombolian, vulcanian) eruptions occurred from Tavurvur and Vulcan, the two main active vents. We study the lava flows, bombs and pumices from five of these eruptions to investigate magma ascent rates and volatile outgassing during ascent. We measured total and connected porosities, permeability, and bubble connectivity that we relate with crystallinity, MND (Microlite Number Density) and MSD (Microlite Size Distribution) of plagioclases and orthopyroxenes. From the application of existing percolation models, we find that explosive products yield a percolation threshold between 50-60 vol% total porosity, while petrophysical parameters of effusive products and some of the bombs can be explained by bubble collapse driven by surface tension. Permeabilities range from 10 -10 m for pumices and bomb cores, while they range from 10 -10 m for bomb rinds and the lava flow. Sub-plinian products show low phenocryst contents (5-15 vol%), microlites generated by nucleation-driven crystallization, or glassy textures due to a lag in kinetic crystallization. Bombs and the lava flow on the other hand, show medium to high phenocryst contents (15-40 vol%) and microlites that crystallized by growth-dominated processes. Sub-plinian MSDs can be interpreted as a partial record of drastic magma acceleration, while bombs and lava flows show slower, more gradual ascent patterns. We estimate that magma feeding sub-plinian eruptions ascends 2-3 orders of magnitude faster than magma feeding vulcanian/effusive eruptions (~1 versus 10 MPa/s). The faster rising speeds cannot be estimated using MNDs due to the important lag in kinetic crystallization, but are instead estimated by the average dimension of pyroclasts and their characteristic timescale of permeable gas escape. Combining petrophysical and textural measurements we suggest that slight changes of initial conditions in the reservoir, such as phenocryst content, can have profound impacts on the ascent rate and generate positive or negative feedback reactions leading to powerful sub-plinian activity or intermittent vulcanian/ quiet effusive activity respectively.