Sorry but I am going to have to jump in and confuse you all a little more.
First of all, a BP pistol is not a firearm according to federal law (PERIOD). That's in simple English. Now as to the conversion cylinder:
"If the replica is not designed or redesigned for using rimfire or conventional centerfire fixed ammunition"
1) You did not design the replica to fire conventional centerfire fixed ammunition
2) You did not re-design the replica. You are just popping in a conversion cylinder. Everything is in tack. You are just implementing an accessory.
Furthermore, if you are going to read the law, read all of it. Don’t stop when you think you found enough to prove your personal view. The definition of “Antique Firearm” continues on to say the following:
"Antique firearm shall not include any weapon which incorporates a firearm frame or receiver, any firearm which is converted into a muzzle loading weapon, or any muzzle loading weapon which can be readily converted to fire fixed ammunition by replacing the
barrel, bolt, breechblock, or any combination thereof”
Wogpotter, you said you didn’t find anything related to the cylinder; however, they clearly tell you what parts of the gun cannot be replaced and cylinder is not one of those items. Let your common sense kick in. If changing the cylinder altered the status, it would have been listed with, “
barrel, bolt, breechblock”.
Furthermore, since the definition of “Antique Firearm” mentions conventional ammunition, let’s examine the GCA definition of ammunition.
"The term ammunition means ammunition or cartridge cases, primers, bullets, or propellant powder designed for use in any
firearm"
A BP revolver is not a firearm. Also, we NOW know that the cylinder is not included in the parts listed that would change the status of this. So you are firing rounds through something that is NOT a
firearm, therefore; the rounds are NOT ammunition by the definition.
Lastly, intuition tells us that if the makers of conversion cylinders were making it that easy for people to break the law, they would have taken so much heat by now, they would have quit.
Conclusion:
If you are not using your GUN (not firearm) with a conversion cylinder in the commission of a crime and you are transporting it in a manner you would transport a FIREARM then you should not have a problem. Honestly, prosecution will be tough if the only time you have the cylinder in the GUN is at the range or in the home for self defense. If you plan on carrying it on your person (which I can’t imagine because of its size), that’s another thing. Even then, just pull the lever and the cylinder will drop right out on the ground… so then the cop has to prove it was actually in the GUN and not being transported apart. The conversion cylinder is probably one of those things that are so hard to enforce, it's let go. MAN, DON’T WORRY ABOUT IT!!! Your Good!