What then are they doing wrong that changes the way the pistol feeds?
The most common mistake made when someone jumps in and starts polishing is that they aren't careful to maintain the defined corner at the top of the frame's feed ramp. It becomes rounded...or "rolled" as I call it. That effectively changes the critical angle of the ramp and usually guides the bullet nose straight into the barrel ramp. That pushes the barrel forward...and as the slide progresses...the barrel starts moving up. If it moves up too early in the cycle, the front corners of the lugs hit the rear corners of the slide's lugs, which...in its extreme...stops the gun cold in a hard 3-Point Jam.
So...our Dremel jockey investigates closer, and sometimes figures out what is happening...and he turns his attentions to the barrel ramp...aka "throat" and begins to grind away at it until he gets the bullet nose over the top as it should. The problem is that he usually destroys a lot of case head support in the process. Depending on how badly he mangled the frame ramp...he may completely destroy it. Bulged and burst cases are the usual result, especially if the headspace is near its maximum limit.
Or...Another one will look at the gap between the frame and barrel ramp and decide that a smooth, seamless transition would make the gun feed better.
The end result is usually the same. I've seen hack jobs like this done on pistols that fed and functioned perfectly, and it was done simply because the hacker thought that it would be even better after a "Ramp and Throat" job that he read about in a gun magazine.
High-end smiths use machinery, jigs, and fixtures to either correct improper
geometry...or they use'em to maintain correct geometry when they polish the areas. This is something that's very hard to do with a Dremel and a buffing head. It's easy to screw up even with sandpaper and a fingertip if it's overdone, and care isn't taken to maintain that all-important corner at the top of the frame ramp.
The reason that I cringe whenever somebody tells me that they'd done a ramp and throat job is because I know that there's a very good chance that they've lost the angles in the process...and I'm gonna hafta work longer on the gun to correct the feeding problem.
Much rather not work too hard, y'know. I've gotten lazy in my old age.
Been hangin' around the Old Fuff too long, I guess.
