Dont forget, "charges dropped" is not always an all clear.
There are some states (PA?) which say "If you have ever been ADJUDICATED" you cannot buy a firearm.
Adjudicated is a very broad term, but simply means if you have ever been processed in a criminal case.
For instance, in Maryland, if you were 13 years old and got caught shoplifting and the charges dropped, even when your 80 years old and a totally clean adult record you still wouldn't be able to buy a firearm.
The same in Colorado.
Yet, an adult who has non-violent misdemeanor convictions is still able to buy firearms all day long .
Insane isnt it?
What I would advise you to do , is get your record expunged.
Even though the charges were "dropped" there is still a court record on you.
Getting it expunged would totally delete your case file from any computers.