Took me about a month. I was shooting a Win 97 trench gun! At a gun show I found another '97 with 32" full choke, took 2" off the barrel (cylinder bore at that point I think, no front sight) and within a few months ran 217 birds straight one day.
A Win M42 .410 full choke was next. This was in the day of paper hulls and Ljutic mono wads, plastic hulls were just coming on the scene. With the M42 I had many 25s, 50s and 75s and managed two 100 straights, still have the CIL awards patches.
Fow fun my buddy and I who also had a M42, would shoot high house birds from #7 with full magazine loads, try to break the bird early then see how many pieces of it we could hit. Several times we each got three and four pieces, total five hits from one bird.
The .410 was a mind blower especially in full choke. The slightest error in lead was a miss.