"2003 (older, I know) there were 730 deaths attributed to "Firearm discharge" and 11,920 deaths attributed to "Assault by Firearm" -- for a total of 12,650 "firearm" deaths."
This is bending the facts, my site is from 2001:
Assault by Firearm: 11,348 (an addition 572 over 2 years is not unrealistic, so I am going to assume its true.
Firearm Discharge: 802 (even though this number is larger then yours, its only 70 away from yours, so again, I am going to assume its true.
However I have a 3rd category, which you accidentally forgot about.
Suicide by Firearm: 16,869 quite a big number...
in any case the total deaths by firearms in 2001 was 29,573, so its not unrealistic for an increase from 29600 to 30,000 in 10 years...