Ammunition chambering mechanism for automatic firearms

A training barrel assembly for an automatic firearm comprising:

• (1) a barrel with a forward muzzle, a rearward chamber end having a chamber formed therein and a generally longitudinally-aligned bore;
• (2) a protrusion extending downwardly from the barrel proximate to said chamber end to serve as a mounting post for a feed ramp extension, said protrusion having a rearwardly facing recess defined by:
• (a) a downwardly-facing first containment surface on the underside of the barrel, rearwardly of said protrusion;
• (b) a rearwardly-facing second containment surface carried by said protrusion and defining the vertical interior end of the recess;
• and
• (c) a generally upwardly facing third containment surface carried by said protrusion, said third containment surface opposing at least in part said first containment surface to further contain said feed ramp extension against displacement in the vertical direction, and
• (3) a feed ramp extension which is non-integral with the barrel and the protrusion, said feed ramp extension being positioned within said recess, extending rearwardly therefrom at the chamber end of the barrel, said feed ramp extension having a guide surface for guiding a round as it is being chambered into the barrel,
• wherein a longitudinally oriented groove is provided within said first containment surface and the feed ramp extension is slidingly fitted into and contained laterally by said groove while abutting against said second and third containment surfaces.