I have slowly been upgrading my stainless Commander. It needed a tighter- fitting firing pin stop so I went with the EGW as discussed in the "amazing" thread. The mod went well, and the stop is no longer "dancing around" in the slide. I radiused the bottom to the .78 spec. Yup, it's a bit harder to rack with the hammer down. I, myself didn't notice much change with the tight radius when firing. I also installed a new wolf 18lb. recoil spring. I was hoping to lessen a condition seen when I first started shooting the gun and that is the brutal beating the cases are receiving when they are ejected. The pix below are from todays test session and are from some 230 ball factory ammo (Independence). The cases have improved since the mods, they aren't getting the nasty, deep ding on the side anymore, but the scraping and bending of the case mouth is still evident. I marked the ejection port with dye and shot some more. The cases are hitting just below the lower opening at the forward "dashed" area (removed dye). Plenty of shaved brass below the area. I would like to reuse the cases so I have been studying this problem a short while, now. I am running the stock hammer spring(maybe 21lbs.?) and the gun shoots well otherwise.
Your dinged brass is coming from one of two places. Either the bottom right side of the port due to ejecting at 3 o'clock... or the top as a result of getting hit by the slide before it clears the port. Look for the brass tracks for the area that hits the brass. Ideally, the case should exit at 2 o'clock or just slightly higher.
For the former, you can radius the bottom corner of the hook lightly, to cause the cases to twist free at a slightly different angle. A tiny radius at the top can also have a telling effect on how and where the case releases.
For the latter... try increasing the extractor tension a little. Sometimes that's all it takes. When the extractor has a little tighter grip on the rim, the case doesn't roll with the ejector's punch as much, and gets a more solid smack... kicking the brass clear of the port with a little more oomph.
The recoil spring load itself can also be a factor. Sometimes a lighter... or heavier spring can cure it... but usually lighter. I've never used heavier than 16 pounds in a Commander. If the brass is ejecting forward of the gun, the slide is catching it on the return to battery. If it's vectoring it straight up and overhead... or you get hit by the brass... the slide is catching it in recoil. Sometimes when it exits forward, the extractor hook is a little long, and isn't releasing the case quickly enough, even with correct tension. Measure the depth of the hook from the back of the stem to the bottom of the slot, and then to the tip of the hook. .035 is about right. More than that, and the case rim can get into a bind between the tip of the hook and the Commander's extended ejector. The brass gets part-way out of the port, but is still in the extractor's grip, or just barely free. The slide hits it and kicks it loose... but it gets dinged.
If you need to shorten the hook, instead of filing it, drag the hook sideways across a medium India stone, being careful to keep it square and level. Go slow and measure often. Under no circumstances should it be shorter than .032 inch, and radius it a little at the bottom corner afterward.
If none of these things help, you may need to play with the shape and length of the ejector.
Sometimes this one can be a pain to fine-tune.
Thank you Tuner! Dang pix didn't get through (message comes back "in progress"). Yup, three o'clock is it. So I should radius the bottom of the hook? I'll try it. Whats the "telling" with radiusing the top of the hook? The tension is set at 26 oz. right now and it is the factory piece. I've moved up to the number three limited class shooter so far with this gun (all the way from the cellar!) so I'm taking the upgrade process slowly. Don't want to mess this gun up! That EGW stop is nice, I'm going to get a couple more, one for the stock and one for my partner (who's butt is getting beat lately by yours truly).
The top of the hook should have the sharp corner lightly broken with a stone.
Lightly... just enough to let the case rim twist free without snagging. This is mainly a little extra measure... just in case it IS a sharp burr there causing a problem. Sometimes, it doesn't change anything... sometimes it's the very thing to cure the problem.
If tuning the extractor doesn't effect enough change to keep the brass from getting beat up, you may need to turn to the ejector. Lightly reshaping the nose with an appropriate angle to direct the brass out of the port usually has a dramatic effect. Looking at the rear of the pistol... break the top right corner on an angle in the direction that you want the brass to go... or so that it will roll up and to the right at about 45 degrees. Easy does it. It only takes a little. Use a stone instead of a file, and test-fire the gun to see what difference it makes.