Started building a walleye jigging rod on an immortal 6’2” MXF. On Rainshadows website the tip is said to be a 4.0 but when I tried to place a recoil 4.0 the tip top has the same O.D. as the rod tip. I tried 2 tip tips and both wouldn’t fit on the blank. When I measured the tip top it measured 1.654 mm.

I guess my question here is should contact Rainshadow about the tip not being 4.0 or is this a situation where I should just order a 4.5 tip top and continue with the build?

You might be able to scrape the paint from the very tip of the blank and get the tiptop to fit. Sometimes that is all that is needed.
Norm

Take some fine Emory cloth to to blank won't take much. May even be able to use a scotch bright pad. If your really worried about the blank take it wrap a tool and polish the inside of tip top. I had to do this on a blank recently. 4 or 5 rounds and she fit like a glove.

If your afraid of going too far up on the blank tape it so you don't ruin the finish.

Tip top sizes are spec sizes - it is rare that any rod blank comes in at exactly the spec'd size. It is very common for any blank to be either one size under, on or one size over, the spec'd measurement listed in the catalog.

Don't sand the blank tip. There is little margin for error there. Sure, you can scrape the paint off and even take a drill bit to the inside of the tiptop tube to perhaps buy a smidgeon there. If it still won't fit, move up to the next tiptop size.

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i have used a small drill bit in my dremel to polish the tube a bit..usually works..

Travis,
If you buy the blank and components in the same place, there are many advantages, you can have them size the tip top and anything like a metal winding checks you might use. It will all fit into the blank tube and many times ship on the same nickel.

I'm with Ben.