How did Springfield zero trapdoors?

[Texcl2]

I was wondering if anyone knows how Springfield zeroed their rifles in the trapdoor era or did they build them to a high enough standard that they were generally close enough? I know most of mine have been almost dead on windage wise which I find pretty incredible, my 1868 print’s exactly to poa at 100. If there was some zeroing going on I imagine it would entail a different rear sight or perhaps bending the barrel?

[Fred Gaarde]

Many years ago, I read how Mr. Buffington was able to take a newly assembled rifle out of the rack and shooting it, he would hit a big post set in the ground 1,000 yards away Five out of Seven times.

[Texcl2]

That’s pretty amazing.

[John S.]

SRS lists a number of "weekly accuracy test" guns in 1887, and a scattered few "accuracy test" entries earlier.
Al Frasca may know more about what these consisted of.