I had a couple of problems with the original design: 1) the guide would hang up on the ejector, 2) it didn't stick out of the bore very far and was difficult to extract, and 3) it would start to slide out when pulling the cleaning rod out.

I modified the original design by adding a cutout for the ejector, lengthening the guide and adding notches to hold on to it, and extending the lug so that it would stay put in the bore during use.