sabotloader: give that piece a chance to break in. We advised D MAN to shoot anywhere from 3-500 rounds or more before he should consider his pistol functionally broken in and maybe a few more to determine true target accuracy potential. I would recommend the same for your Springer. Your Government Model is a real workhorse and a healthy piece of machinery - it needs a chance to settle in.
The marks you reference from the extractor are probably still due to some need for break-in but may also be due in part to the +P loads you were using. Although you have replaced your recoil spring with a 20 pounder, that only abates recoil, not the pressure of the ammo you are shooting and high pressure ammo (+P) usually shows some pressure signs on fired cases, including extractor marks. Chceck the rear of the cases of both the +P and ball ammo to look for differences in the imprint left by the ejector. Your +Ps may not have a more noticeable imprint, some +P ammo seems hotter but may not properly cycle your pistol, especially with the heavier spring and buffer. Other marks you may find on the fired brass cases might be magazine lip scratches.
Bent cases at the case mouth are usually caused by the case still caught by the extractor as the slide goes forward stripping a new cartridge from the magazine - the cases impact on the outside edge of the ejection port. This is one of the side effects of using heavy recoil springs and recoil buffers. They don't allow the slide to go all the way rearward against it's designed stops which allows for proper ejection of spent cases. Truely, with the 20 lb springs I would remove the buffer. I don't think you need it, certainly not with ball ammo, and that spring should handle +P without the need for additional buffering of the frame unless you intend to feed the pistol a very steady diet of +P ammo on a very regular and consistent basis but I still think the heavier spring is all you really need.
Just a couple of thoughts fer ya (lol). HTH. Mikey.