You may have heard about Joe Biden's proposal to require current owners of "assault weapons" and "high-capacity magazines" to register them under the National Firearms Act. Here's an overview of what that registration currently entails. https://joebiden.com/gunsafety/ 

This is the application to make/register an NFA item with the ATF. If you wanted to turn a shotgun into "short-barreled" shotgun, for example, this is the form you would use. https://www.atf.gov/firearms/docs/form/form-1-application-make-and-register-firearm-atf-form-53201/download

You'll need to fill out your name, address, and contact info. You'll also need to fill out firearm's information. Magazines do not typically have serial numbers, so I'm not sure how that section would work for those.

Next you have to "specify why you intend to make" the firearm. Note that when it says "make", it doesn't necessarily mean making a gun from scratch. It also means "making" a non-NFA item into an NFA item (such as by shortening the barrel on a shotgun).

Next is the page for "law enforcement notification". Many of these questions are similar to those asked when buying a gun. You will need to fill these out and attach a passport-type photo of yourself to the page.

Last, you will need to provide a method of payment for the $200 tax that must be paid *for each NFA item* you intend to register.

You will need to make three copies of this form for every item you wish to register: Two for the ATF, and one to give your state/local police so they are "notified". You will also need to submit two fingerprint cards.

Additional info: If you later intend to (1) Bring your NFA item to a different state (for most items) or (2) change your address, you must notify the ATF. Also, if you have your NFA item with you and an ATF agent asks to see your registration, you must provide it to them.

How long will it take the ATF to approve your registration? Currently, wait times for individuals are about 200 days, but there's no telling how long it will take if Biden's proposal passes and the ATF starts receiving millions of applications. https://www.silencershop.com/atf-wait-times 

What this means for you: Under Joe Biden's proposal, if you intend to keep the three 15-round magazines that came with your Glock 19, you will need to pay $600 while giving all of the above-mentioned information to the ATF and your state/local police.