Error in Kuhnhausen Shop Manual

[ssgross]

I sat down last night to continue adding to my own shop notes. After a few double takes and head scratching, I sent the following letter to Heritage Gun Books, publisher of the Kuhnhausen-VSP shop manuals. Being this is such a great book (as are the others) and a go-to reference for so many of us here, I thought I would post for others to find. It's not hard to observe for anyone paying attention to or wondering about max/min barrel draw when swapping or installing a new barrel.

Dear Heritage Gun Books,

I am writing to bring to your attention an error in some data contained in Jerry Kuhnhausen’s The U.S. .30 Caliber Gas Operated Service Rifles: A Shop Manual, Volumes I&II, Bench Edition, 1995. Specifically the table at the bottom of Figure 87, page 97, concerning Final Barrel Shoulder Draw incorrectly reads:

Degrees Rotation ...|... Final Barrel Shoulder Draw
15 degrees ...|... *5/16" rotation
12 degrees ...|... *1/4" rotation
10 degrees ...|... *3/16" rotation
*Rotational draw figures rounded off to nearest 1/16”

The Final Barrel Shoulder Draw should instead read 5/32”, 1/8”, 3/32”, respectively, rounded to the nearest 1/32”.

Indeed, the exact distance between scribe marks is given by 1.100*sin(?/2), where 1.100 is the barrel shoulder diameter recorded on page 95 and ? is the angle of rotation. Perhaps Mr. Kuhnhausen mistakenly used 1.100*sin(?), which gives the values in the table as published.

EDIT: apparently our forum does not like to render thetas