A kit for modifying a firearm includes an adapter, and the adapter includes an external threaded surface configured to detachably couple to an internal threaded surface of a receiver of the firearm. An adapter bore is disposed opposite the external threaded surface, and the adapter bore is configured to receive a barrel of the firearm. The kit further includes a securing element, and the securing element includes a securing element bore configured to receive the barrel. The securing element is configured to detachably couple to the adapter and thereby secure the barrel to the adapter.