Interesting, Jim.  I had never thought of using a sheet of yellow legal paper for a background before.
FWIW, in years gone by when I used to make a lot of those valved priming horns, I kept one valve tip as a guide. 
I would install a good one in the tip and after the epoxy had set up, I would take the working parts out and then screw in the  old tip.  Then I would sand down to that, producing a tapered horn tip that followed the exact size of the screw in end.
I also had a set of numbered drill bits and I would open the hole in the screw in tip one drill size larger and I would polish the plunger and make sure the vent at the bottom was free of any burrs.
It was a PITA, but it made the horn work so much more smoothly.
I also kept a supply of replacement parts (especially springs) in case something got lost in the manufacturing process.
John

Hooked up with Eric yesterday to continue the testing of our homemade antique muzzleloader propellent.
 Here's the results to date.
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 As you can see the commercial stuff out preforms the AMP but I'm still happy with these results.
 The powder is Milled for 24 hrs. There is debate regarding better performance with longer mill times, 36-48 hrs
That's something I'll have to look into.
 As far as fouling, the 76 12 12 had softer fouling, less crunchies left behind than the  77 13 10.
 I'm told that's due to the sulfur content, less makes harder fouling??
  So still more playing to do but the 76 12 12 will be my go to recipe for the foreseeable future.
  Oh and accuracy at 25 yds was spot on with all the powders tried.
 Kevin

Hers another project finished that has been in a box for 10 or more years, have 5 of them to finish before I finally start the Kibler!

Bison priming horn

Too many issues for me this year and very little shooting done,    ... but things will be different come next year!