I've never worked with Delrin. I know all of the advice above applies to hickory, from which I have made a bunch of rods. I hope you'll let us know how it goes, fitting tips to Delrin.
Just a couple of things...
You can use a tubing cutter to make the cut for the shoulder on a wooden rod when you fit the tip, but holding the blade of a sharp utility knife or "box cutter" on the rod while you roll the rod on a flat surface works just as well.
In pinning the tip, I fit the tip or ferrule to the rod first, then drill a slightly undersized hole through the ferrule and the rod for the crosspin, then re-drill just the metal ferrule (both sides) to a size that allows a slip or light press fit for the pin. I put a little epoxy in the hole before tapping in the pin. I cut the pin off flush when the epoxy has cured, and just file it flush. I've never found a need to peen the ends of the pin.
I clean the inside of the ferrule or ramrod tip with acetone on a Q-tip before gluing it in place. This helps achieve an optimal bond.
The ferrule may be epoxied or secured to the rod with hot-melt ferrule cement, as is used for arrowheads and threaded inserts. Both give a very strong bond, when done properly. However, before gluing the ramrod tip or ferrule, I put a well-greased 3/8" machine screw of the appropriate thread size into the threaded hole in the tip or ferrule. Don't forget to grease the very end of the screw! The screw prevents the epoxy or cement from filling in or fouling the threaded hole, and the grease keeps the cement from sticking to the screw.
I don't know if you really save any money making your own rods, but I do believe you can make a better rod than you can buy. That's what matters.
Good luck with your project!
Notchy Bob