The Abbot cannon is a large 105mm Cannon fitted to Main hardpoints.
The venerable Abbot, pre-colony tech that hasn't changed in over a century. Sure the munitions have evolved, and the exact metal composition might be a bit different now, but along with the Mãe Dois and the König, this weapon is a perfect feat of engineering. Put ten thousand rounds through it and your shots will still land just about where you aim. Age and reliability mean you can travel to just about any colonized world and find an Abbot perched off some vehicle or another. It's a steadfast weapon that's good in just about any situation.