from
http://www.directactionsolutions.net...n-explanation/
First of the SSE cannot be done on every pistol that is not on the California Roster of Approved Handguns. Most of the guns we offer require us to purchase extra parts to make the gun meet the dimensional requirements of the SSE. (The gun must have a minimum barrel length of 6 inches, and an overall length of 10.5 inches) Most guns are not even close to this. The solution is to purchase a new barrel from manufacturer or source one from an aftermarket company. In some cases this may cost as much as $5oo.
So now that we have found a barrel, we need to lengthen it so it meets the SSE requirements. Usually lengthening the barrel will help us meet both dimensional requirements. The final modification is to manufacture some sort of block that can be inserted into the magazine well. The purpose of this is to change the gun from a semi-auto magazine fed firearm to a single shot firearm that can only be loaded one round at a time. With the longer barrel installed in the slide and the block installed in the magazine well, we have now created a Single Shot Exempt Pistol. This pistol is now exempt from the California Roster of Handguns, and legal to sell in California.
When you come into purchase your SSE pistol, it will be configured with the longer barrel and magazine block installed. You will start your ATF and Department of Justice paperwork and start your ten day waiting period. When you return to pick up your firearm, you will sign and complete all necessary documents, and receive your SSE pistol. The gun is now yours.