Ramped up

This is one of those small but very important 1911 detail things, the feed ramp.  I chose to leave it completely uncut and in retrospect I should have just machined it along with everything else.  But there is a library's worth of discussion and argument on what the "best" feed ramp angle should be and I wasn't sure how the barrel would fit so I put it off until later.  And now it's later.  After a whole lot of reading, I decided that despite all the discussion and arguments, it is not, in fact, rocket science.  There are millions of these things out there from hundreds of companies, spanning over a century of manufacturing, and they can't all be the same.  I chose the most commonly recommended ramp, at 31.5°.  I started by laying out some guidelines where the limits of the ramp should be, the most important one is that it needs to be .030" from the throat of the barrel.

Not trusting myself to do an ultra precise angled setup on my little mill, I elected to do all the metal removal by hand.  I can already feel the gun community shudder as I start attacking this with my Dremel.

I may look stupid, but I'm not dumb, and I'm not doing all of it with the Dremel.  I'm just doing the roughest of roughing.  The rest of it will be done with sandpaper.  But how do you make a very precise angle with sandpaper?  With a happy coincidence and a stupidly simple tool.  You see, if you put a 1/4" rod through the magwell so that the back of it rests on the MSH side and the front lays on the feed ramp, it ends up being exactly 31.5­°.  If you then have a 7/16" diameter circle tangent to where it contacts the ramp, you have the exact diameter you need for the feed ramp.  I checked everything in Solidworks, and it all works out perfectly.  I made my tool with some 1/4" rod, and a 3D printed sleeve.  I put a center line on it so I could be sure it stays straight up and down while being used.

Wrap the sleeve in sandpaper, hold the frame in something secure, and have at it. I taped off as much as I could to keep from getting everything scuffed up.

I sanded using progressively fine sandpaper up to 400 grit, and stopped when I hit the barrel setback line I had scribed.

Then I hit it with some Mother's Mag and Aluminum polish to shiny it up.

I don't know how accurate it actually is, but it feeds very well with my dummy rounds.  We'll have to wait to see how it works with actual bullets.