Here are a couple suggestions if you want them. First great story. Better than most written like this.

If you continue, think of not continuing in the same spot. Move forward in time - perhaps to a quiet drive home with her mom and work in brief flash backs.

Don't have her mother go into a long brainy rationale for what they did. Just let it pass.

Have her missing - even longing for more. That was one of the best parts of what you have done so far. Have her ask her mother for a gun - loaded - to use in her cunt with the safety off or better yet safety broken.

Then go to the next visit. One last suggestion - have the cuntlet work on expanding and deepening her hole to make a better gun rack. That would be fun to hear her talk to her mother about!

Great work - thanks,