As there is not much in the way of information online about the EM1, I thought I might do my part in adding to the web library by documenting what little I have to offer on this firearm.
The Erma Werke EM1 is a .22LR version of the M1 Carbine. They were manufactured in Germany from 1966 to 1976. Iver Johnson also sold EM1's in the 1980's. An Erma Werke EM1 listed in a recent, $0.01 to start - no reserve, Gun Broker auction sold for $280.00. I have seen them listed as high as $350.00, I purchased mine for less.
Parts for an EM1 are hard to come by. A good bet would be to try Numrich Gun Parts Corporation first. Numrich also has a detailed exploded parts view here. Firing pins can occasionally be found on Gun Broker or even Ebay.
Loosen the front band screw, pull the band forward and remove the upper hand guard.
Remove the rear guard screw that is located behind the trigger guard.
Remove the stock from the barreled action.
This is as far as is usually required for general cleaning of an EM1. An aerosol based gun cleaner with lubricant will adequately clean the action. The upper receiver is cast and can easily break, and there are small parts that can disappear. I have also read a few reports about the operating slide breaking, but I am not sure how that could happen.
Another common failure is a broken firing pin. To replace the firing pin, further dis-assembly is required:
Remove the slide spring and slide spring guide by compressing the spring and pulling the guide forward and out of the lower receiver.
Remove the receiver screw and the two trigger housing retaining pins.
To remove the upper receiver, pivot as shown in the following images. Note the ejector and sear release assemblies. Pay attention to how they are assembled so that you can get them back together correctly. With the bolt partially retracted, you can remove the slide.
Raise the recoil plate from it's notch and remove the firing pin spring, firing pin and the bolt.
One common failure on this rifle is the firing pin. Mine was broken when I purchased the gun (might be why I got such a good deal on it). I could not quickly find a firing pin, so I made one.
The black firing pin is the OEM (purchased off of Ebay) and the shiny bright one is the one I made. You will notice that the length of the striking portion of the pins is different. When I made mine, I did not have one to use as a template, I made mine so it extended .030" beyond the bolt face. I used A2 drill rod and decided not to heat treat it. I have over 400 rounds on the new pin without any deformation, so it appears that heat treating is not necessary. The length of the smaller diameter of the OEM firing pin is .265". If you can not find a new pin, a machine shop should be able to knock out a new one for you in no time.
Prior to reassembly, ensure that the sear spring and the sear spring plunger are properly oriented under the sear. The plunger goes down, the spring against the sear. The following image is of an incorrectly installed spring/plunger.
To reassemble, just reverse the steps you used to disassemble the rifle. Take care to align the ejector and sear release assemblies as shown in the images above.
If you have more information on the EM-1, please mention it in the comments. If you have better images, email them to me and I will add them to this post.
I hope this information is useful.
A comment to this post prompted me to disassemble my EM-1 and take an exploded view image of the trigger group.
This should help with "Where does this spring go?" questions.