Page 49 and 50 of Kuhnhausen vol 1 details a 45 degree chamfer on the disconnecting edges of the slide and barrel lugs. This chamfer is supposed to allow extra clearances to prevent lug drag. A removal of .005" of material is stated as the maximum for each lug (10%). Does this relate to the 0.20" clearance between the barrel hood and slide lug as suggested in the timing test article by Schuemann barrels? Does anybody still do this chamfer? Any first hand experiences with this process and its consequences?
Quote:
Does this relate to the 0.20" clearance
No. The chamfer provides a little extra fudge room that keeps the lug corners from catching as the barrel times up into the slide. Not an issue with ordnance-spec pistols, but could become one in certain pistols with tightly fitted barrels... specifically between hood and breechface... because zero clearance there causes te barrel to cam up earlier. Slide and barrel lug corner contact as the gun returns to battery is what 3-Point jams are made of.
But, it doesn't help a thing if the linkdown/drop timing is wrong.
1911Tuner, very interesting. Btw, just caught a mistake. I meant 0.020" as opposed to 0.20".
Quote:
I meant 0.020" as opposed to 0.20".
Didn't catch that.
To get a better understanding of how the bind occurs, you can exaggerate it by placing a .010 inch shim between the breechface and the barrel hood as you guide the slide into battery. The shim causes the barrel to time into the slide too early, before the slots are lined up with the barrel lugs.
FWIW, the blueprint of the USGI barrel calls for a 0.005 to 0.015 inch by 45 degree chamfer on all 5 corners.
FWIW... Chamfer the barrel lugs if you like, but leave the slide's lugs alone.
Tried the shim, and it does exactly what you say. FWIW, I think Kuhnhausen, at least when the book was written, believes that it assuages link down to some small degree. If you have vol 1, see page 49, fig 4, and the subsequent write up that leads into the chamfering business.
Then again, Kuhnhausen also believes that barrel contact on link down should be made solely to the frame bed. Could just be outdated thinking since the book was written in the 80s.
Quote:
I think Kuhnhausen, at least when the book was written, believes that it
assuages link down to some small degree.
Yeh. Wouldn't be the first time that Kuhnhausen shot himself in the foot...
Go to the tech section and find the write-up called:
"How the 1911 Really Works" by Jerry Kuhnhausen.
If you understand simple Newtonian physics, the error will jump out at you.