Those of you wondering about the size, check out the
http://halo.wikia.com/wiki/M6D_Pistol entry at the Halo wiki. The pistol is actually about the size of a Desert Eagle(still massive for a handgun) There are some reference pics at the bottom which includes the magnum variant which looks much more manageable due to the lack of scope, however the frame is still identical. Another issue with the scale comes from entity scales in the Halo engine. The weapons, all of them, are scaled to match the Masterchief, not the Marines. This ensures that their Hero model always looks proportional to the arms he is carrying. However, the poor marines end up carrying slightly oversized models. The final contributer to the apparent oversized look of the M6D is the massive handguard. The wiki entry only mentions the length(barrel to butt) of 26.7cm, or 10.5 inches. A Desert Eagle is is 26cm, or 10.25 inches. The long and short of it: The pistol is big, but not 'that' big.
I'm curios to know what the length of your pistol is. By the looks of it, you might be pretty close to the actual size. Nice tape work BTW!