My grandfather had loaded a .45cal percussion black powder rifle( he has passed on).  I do not know how long it has been loaded but my uncle tried to shoot it and it would not fire. I do not know how long it has been loaded but it sounds like for a very long time. Im the firearms guy in the family so they came to me. I know nothing about black power weapons. I have yet to get my hands on the rifle but its on the way. Im worried it may have been improperly loaded as the my grandfather was 93 when he last used the rifle. What is the safest method of unloading for this situation?

sometimes you can blow it all out with an airgun in the nipple

Google black powder bullet puller.  

I would take the rifle apart (barrel out of stock) and secure it in a vise pointed in safe direction and with some sort of improvised bullet trap. Then I would carefully remove the nipple from the breech and see if I could determine if any powder is present in the barrel by carefully inserting a small pick in towards the chamber. You mentioned that the rifle would not fire earlier. There may only be patch and ball, no powder..... Next I would pour in a decent amount of oil and let it soak into the breech/chamber. After a couple of days, I would very carefully to use a BP bullet puller, and see if I could remove it.

There are two alternative methods that might works also.
A. Using a CO2 shot discharger, sold by Mid Southshooter supply, Midway etc. screw it onto the nipple push button with rifle pointed in a safe direction, then verify clear chamber. Clean thoroughly and put it back into service (if you are a BP shooter)
B. Depending on the method the barrel was built, it may be possible to put the barrel in a vice (as above) and unscrew the rearmost portion of the barrel aka the breechplug. If you can do this then cleaning is like for any normal breechloading just using proper solvents for BP.

IM/Email if you have any questions, I'll try to help.

I have a screw shaped addition to a cleaning rod for removing the actual ball, once that's done I remove the percussion nipple and use compressed air to clear the powder and wadding.

The first part is done very carefully with your hands on the SIDES of the cleaning rod with leather gloves.

this rile may have been loaded for 15 years. I'm interested in the air compressor method is there an attachment I can find, buy or recommended? If that fails is still safe to try the oil and bullet puller? Thanks for the replies.

Here you go.

https://www.buffaloarms.com/b-i-d-co2-blowoff-inflator-discharger-rmc1082

I have successfully used one of these with the rubber front piece, and my compressor.



I had the barrel clamped in the vice and had removed the nipple.  I also soaked the powder with WD-40.
You might want to soak the powder before you try anything anyway.  Couldn't hurt and safer is better.

GREAT THANK YOU SO MUCH.

So, did you get it unloaded?  If so, how did you go about doing so?

Remove nipple.
Sprinkle powder into hole
Replace nipple
Cock hammer
Cap nipple
Point muzzle in safe direction
Squeeze trigger.

Seriously.  Status report? Did it result in some terrible accident?

I bought a flintlock on GB  that came loaded with a 69 gr ball. I soaked the load with soapy water  for a day then used a screw type ball puller on it. The ball came out with no trouble. After inspecting the powder and patch I believe that flinter  was loaded for a very long time, decades.

I used to have a tool that used a CO2 cartridge.  Think it was called a Silent Distcharger or something like that.