My name is XXXXX XXXXX I am an experienced criminal lawyer.
Unfortunately, while it's very commendable that you've moved on from your criminal offense and become a stable, lawful and productive citizen, once you have a felony conviction, the Federal government as well as the state, will strip you of your gun rights.
There's no longer any provision to get Federal rights back through the Federal government, so the Federal bar to your second amendment rights is technically a lifetime bar. However, the government has agreed that If yours was a state conviction and the state restores all of your civil rights including your gun rights OR if you have your offense set aside, expunged or pardoned, the Federal government will lift its disability. That means you should have your federal rights back too.
My research indicates that Kansas will restore a felon's firearms rights five years after the completion of his release from incarceration or of his probation, so long as the conviction was non-violent. As your drug felony was non violent, if your sentence was fully discharged (completed) at least 5 years ago. You would be eligible for the automatic restoration of your state rights. Kan. Stat. Ann. 5 214204(a)(3)
So if you have completed your sentence more than 5 years ago, you should have your Kansas rights back. If you try to purchase a firearm and fail a NICS check and can show official proof of your conviction and then the statute under which your rights were restored, you can appeal the Federal decision and the Federal government should lift its bar. You can find more on appealing a NICs denial here
If you are denied on appeal, the Federal government is going to require a pardon or an expungement, in order for you to restore your rights.
If you cannot reapply for an expungement, you would need to try to get a pardon from the governor of your state
. I have linked you to where you can find the information and forms.
There are also lawyers who specialize in this kind of law if you don't want to do this for yourself. You could price one by contacting the Kansas State Bar Association's lawyer referral service.