Tank bunkers might be a pain in the ass when infantry runs into them unprepared, but a tailor-made solution is something else. I give you, the MG Panzernest, or as the Red Army nicknamed it, "Crab":
"This armoured container is a machinegun nest. Height: 1.8 meters, average diameter: 1.6 meters. Armour near the firing port: 115 mm, in the lower part near the hatch: 35 mm, in the upper part: 45 mm. The firing port is placed in the narrowest part of the container and contains two openings, one for observation and one for the machinegun. The size of the firing port is 160 mm by 110 mm. The firing port can be closed completely from the inside with a steel door. The entrance hatch is on the opposite side form the firing port. A machinegun is mounted on a special mount, giving it 45 degrees of range.
Observation of the battlefield can be done through periscopes, which can be covered up. In order to install the container, a trench 0.8 meters deep is dug. After installation, the container is covered in dirt. In most cases, the container is invisible on 1:8000-1:10000 scale aerial photographs." - Types of German Field Fortifications, November 1943
MG Panzernest from the top and from the front
MG Panzernest from the front. This photo makes it very obvious why these things cannot be seen from the air.
Rear side of the MG Panzernest.
Machinegun mount.
Extracted MG Panzernest at a trophy exhibit in Moscow.
MG Panzernest in transit and before installation. The metal shell is carried upside-down and flipped into the trench.
Via dr-guillotin.