What is a recoil spring reverse plug?

"DNS"...
The reverse recoil spring plug is approximately .050" larger in diameter in the rear of the plug and greater in diameter for a length of .375" also at the rear of the plug. The slide 'spring guide'is counter drilled from the rear of the slide to the previous dimensions to accommodate the new reverse plug. No nipple is required on the front of the plug since they are used with a bull barrel. And, since there is no barrel bushing a nipple is not required on the spring plug to prevent'rotation' of the bushing under firing load. Take down of the recoil system is usually with a "paper clip"
placed into a hole drilled into the FLGR with the spring under compression. Once the spring is captured it is removed to the rear of the slide as a contained unit. There are other variations of the reverse plug such as the reverse plug with a nipple on the front...kind of a unique situation where the slide has been cut for a reverse plug but a regular barrel and bushing are used. If a standard spring plug is used with a slide that has been cut for a reverse plug you will get battering and mushrooming of the back end of the slide spring guide, and, sooner or later the slide will break ! Remember the back end of the spring tunnel which hits the impact surface of the frame on recoil has been reduced .050" in diameter to make room for a reverse bushing! Its strength is not restored unless the reverse bushing is in place and the plug is flush with the end of the slide for uniform impact on recoil. On the other end the reverse plug nipple has to be adjusted to put no forward pressure on the barrel bushing so as to not cause fatigue and breakage of the bushing
...But on a positive note this system if adjusted properly puts no pressure on the barrel bushing and should theoretically maintain a more accurate bushing fit over time since there is no forward pressure on the bushing to cause excessive wear. Other examples of the modified reverse plug can be found on officers model 1911s and some Springfield Champions...
FYI, there is a picture of the reverse plug with nipple at George Smith's "EGW" website under new products as well as a regular reverse plug, and other interesting products.
Sincerely-Barry