Blueprints
A two-half, print-on-legal-paper layout template for the Mk III receiver tube with hole positions and overall length (18-1/16 in), plus a note on lengthening for a bolt extension. Hobbyist drawing, not official.
Reference line for joining the two plan halves 7/ 8" 1 1/8" * overall tube length 18 1/16" 9/ 16" (3/8" 7/ 16" 1 7/16" drill) 3/ 8" 3/ 8" 6" 2" 1" 1 1/8" 1 5/8" 3 3/4" (3/8" 11/ 16" 1 11/16" 9 1/2" to end of tube (1/4" drill) Corners may be left rounded 1/ 4" These plans are for educational and entertainment purposes only. All NFA laws apply. Notes - Print out on 8 1/2" X 14" (legal) paper - for semi-auto conversion with bolt extension increase distance * to 2 1/4" 1 1/8" 1" drill)