I have a doserless M4 MCAP.. but I feel this is diverting the thread..
The joke here is the spring loaded Elektra Microcasa a lever is notorious. We're talking to the point of the right days following bean roast, the grind quality and amount within the puck. Operation is sweet and to the point - you prep, lock in the portafilter and pull the lever down. Boiling Water transfers across into the group head and then you let go of the handle, the water supply is cut and it pressures the water through the puck.. the only thing stopping a shotgun of superheated steam is your skillfully prepared puck.
If the puck is too permeable (dry, old beans, bad grid, bad tamping) then the spring will hammer the water through resulting a massive spray from your cup everywhere.
If the pick is too impermeable (oily beans, too close a grind, over tamping) then spring will not be able to push the water through the puck.. and it will sit there.. fully loaded with steam.. and no backoff relieve valve.. when this occurs you need to defuse by taking some strain off the sprint and wrap the thing in a towel.. and pray as you unclip the portafilter.
Oh.. did I say that the group head heat is not regulated.. so if you don't regulate it then a cold GH=sour shot, over heated GH = acidic shot.. so the number of shots you can do at a rate is dependent on you... plus the boiler takes 15 minutes to heat to temp with only enough water for two Italian-sized cappuccinos.
If you've tamed it.. then you're rewarded with one of the most stunning espresso shots and the most stunning velvety milk foaming.
So it's sort of an autistic's nightmare due to the unpredictability even when following ridged prep steps.