I do not live in an area with lots of woodcock though we do have some along. Most of the ones I killed I used an ounce of #8 from a choked 12 gauge. I do recall shooting "One" when I was out rabbit hunting & near stepped on one. Don't recall now what gun I was using but remember I shot it with a fairly light load of #5. He hit the ground as Jerry Clower would have said "Graveyard Dead".
#9 is as small of shot as I would ever want to use for any hunting & that would be only for very small loads for use on very small birds at short range. As an example oz of #9 would have about the same pellet count as 1 oz of #7. The #9 would not of course carry pellet energy equal to the #7 so would be useful only when up close & Cosy. Might be good for a 2 .410 load for woodcock. Personally I would still prefer #8 for quail. Though I have never had the privilege of engaging in it I understand that both #9 & #10 was/is popular for Rail Shooting from small bore guns.
In "The Gunsmith's Manual" published in 1882 by Steele & Harrison they show six US shot towers. For "Soft" shot #10 varies in count per ounce from 815 to 1006. For "Chilled" shot they show only the Sparks & Tatham towers which for #10 have respectfully 960 & 868 per ounce. For the Soft shot Sparks & Tatham showed 950 & 848 per ounce. The sizes from the Tatham tower is incidentally the sizes which are in current use so have remained essentially unchanged for at least 136 years & probably longer.
Different alloys will of course very the count slightly as seen in the soft vs chilled. The antimony in the Chilled is lighter than the lead thus pellet count is a bit higher.
The chart at this point does not show a # 7 size. As a compasion Tatham listing for #8 shows 399 for soft & 409 for chilled which is essentially the same as modern sizes show.
