According to the report, any random part that the user could “readily” convert into a firearm would be subject to ATF regulations. As in the past, the document doesn’t define what the term “readily convertible” means. This term could be that any block of metal could be “readily convertible” into a firearm. In fact, the document shows that the ATF used a court case where it took the user eight hours to covert a kit into a gun. The document does highlight the need for a complete machine shop, and qualified workers to complete a firearm would not fall under the proposed rules.
The document would mean new 80% AR-15 lower receivers, chunks of metal, would need a serial number and require the buyer to obtain a background check before the seller could transfer it because it could be “easily” convertible with “readily available” tools. The document demonizes the modern sporting rifle by highlighting that Eugene Stoner originally designed the rifle for military use.
I strongly urge you to read the rest of the article: https://www.ammoland.com/2021/04/atfs-new-rules-take-on-ghost-guns-serializing-blocks-metal/