Scott, it looks like if your ammo was in the trunk, you should be okay...
Here is the code on transporting in/through DC.
http://www.lexisnexis.com/hottopics/dccode/
D.C. Code § 22-4504.02
DISTRICT OF COLUMBIA OFFICIAL CODE
Copyright 2013 by the District of Columbia
*** Current through April 1, 2013, and through D.C. Act 19-658 ***
DIVISION IV. CRIMINAL LAW AND PROCEDURE AND PRISONERS
TITLE 22. CRIMINAL OFFENSES AND PENALTIES
SUBTITLE VI. REGULATION AND POSSESSION OF WEAPONS
CHAPTER 45. WEAPONS AND POSSESSION OF WEAPONS
D.C. Code § 22-4504.02 (2013)
§ 22-4504.02. Lawful transportation of firearms
(a) Any person who is not otherwise prohibited by the law from transporting, shipping, or receiving a firearm shall be permitted to transport a firearm for any lawful purpose from any place where he may lawfully possess and carry the firearm to any other place where he may lawfully possess and carry the firearm if the firearm is transported in accordance with this section.
(b) (1) If the transportation of the firearm is by a vehicle, the firearm shall be unloaded, and neither the firearm nor any ammunition being transported shall be readily accessible or directly accessible from the passenger compartment of the transporting vehicle.
(2) If the transporting vehicle does not have a compartment separate from the driver's compartment, the firearm or ammunition shall be contained in a locked container other than the glove compartment or console, and the firearm shall be unloaded.
(c) If the transportation of the firearm is in a manner other than in a vehicle, the firearm shall be:
(1) Unloaded;
(2) Inside a locked container; and
(3) Separate from any ammunition.
HISTORY: July 8, 1932, 47 Stat. 651, ch. 456, § 4b, as added May 20, 2009, D.C. Law 17-388, § 2(d), 56 DCR 1162.
NOTES:
SECTION REFERENCES. --This section is referenced in § 7-2502.01, § 7-2502.04, § 7-2505.04, § 7-2507.05, § 22-4505, and § 22-4508.
LEGISLATIVE HISTORY OF LAW 17-388. --For Law 17-388, see notes following § 22-4501.
EDITOR'S NOTES. --Section 3 of D.C. Law 17-388 provided: "Sec. 3. Savings clause. Nothing in section 2 shall affect any action, proceeding, or prosecution commenced before September 16, 2008. Any such action, proceeding, or prosecution shall continue, or may be enforced, in the same manner and to the same extent as if the amendments made by that section had not been made."