Getting bonked in the noggin is not conducive to good shooting.
What's happening is the case is not clearing the ejection port before the slide comes screaming back and hits it causing the case to fly like a line drive straight back at your head.
There are two major scenarios to be considered.
- The extractor loses control of the fired case as the slide moves rearward. The case ends up floating freely in the space above the magazine until the forward edge of the slide's ejection port contacts it and drives the hot brass straight back at the shooter.
- The empty case makes solid contact with the ejector which drives the case horizontally into the slide area below the ejection port. This causes the case to pop up in time to be smacked by the forward edge of the slide's ejection port which drives the hot brass straight back at the shooter.
Before you clean the pistol check all around the ejection port for brass smears for evidence of this contact.
As you point out the problem is with either the extractor or the ejector. In my experience, the extractor should be your focus first. Once you get it squared away the pistol needs to be test fired to see if the problem has been solved. If not, you can move on to the ejector.
Keep in mind that lowering the ejection port is commonly done to provide a larger window through which the empty brass can fly. However, this should be your very last option.
Here's a tutorial on how to fit an extractor that should proves useful to you:
L I N K.
Do not waste your time or money fiddling with the ejector until the extractor is correct.
As for the ejector, I've had the best results using extended ejectors with no angle on the nose in shorter than 5" 1911s. Here's a lousy picture of one of my Commanders showing the ejector poking through the breechface. You can see the nose is perfectly flat with just the edges gently rounded.
Here's a pic of the same ejector during the fitting process showing how long the nose is. It is so long that live round (factory FMJ) ejection is just barely possible. In other words, the ejector is short enough to allow live round ejection but no shorter than absolutely necessary. The reason for the long nose is to get the empty case out of the ejection port as soon as possible. Why? Because these short slide 1911s have a much smaller time frame in which to operate to kick the brass out than a 5" 1911.
In any event, these long ejectors that I install combined with the correctly fit extractors have proven to be utterly reliable.