When the price of legal guns skyrocket, you give incentive for smugglers to bring in lower cost, untraceable pistols for the criminal world. It is not hard to backward engineer a semi auto pistol in the Third World.
Actually some "3rd World" countries already makes some fine firearms, there's no need to backward engineer. Some like Argentine bought manufacturing rights from Colt long ago for the 1911. Taurus pistols are made in Brazil and Arcus (fairly new on the scene) is made in Bulgaria. And Albania of all places makes a better than average AK.
The bottom line is that this Bill is just stealth gun control.