ideal buckshot size for 20 gauge?

[DutchmanDick]

What is the "ideal" size buckshot for a 20 gauge? By that, I mean what will more-or-less neatly stack in layers? Seems like 00 buck might be a bit large, as 2 of them next to each other is just over bore diameter on my NWTG (.618 bore), and just under bore diameter on my Middlesex howdah pistol (.629 bore).

 

[Joel/Calgary]

The "ideal" size depends in part in what you are loading for - defense, deer, coyotes, etc. You want the shot sized to sit in even layers, or the forces involved will wedge them against the sides, with much greater deformation, and scrubbing on the bore if not protected. The proportions between the diameter of buckshot that would sit in even layers and the diameter of your bore (or the minimum of your choke, or inside the shotcup, or inside the shotcup passing through your choke, etc.) are:

- 2: 1/2 * the minimun diameter of bore, choke, or inside of shotcup
- 3: .4639 * the minimum diameter "
- 4: .4142 * the minimum diameter "
- 5(+1 in centre between layers): .36± * the minimum diameter "
- 7: 1/3 * the minimum diameter "

I suspect that normally, one would use something a hair smaller than the "exact fit" size to allow for imperfections, fouling, etc. I've never seen anyone calculate for layers of more than 7 - probably by then, one can just treat them as loose shot.

Regards,
Joel

 

[CoyoteJoe]

That's an interesting table you present there, I'll have to file that for future reference, thanks!
As to 20 gauge buckshot, there is probably good reason why ammo makers load only two sizes, #2 buck and #3 buck.

 

[tg]

in Oregon there is a min size of shot leagal for Deer so one cannot get the best stack and be leagal for Deer but I found that the .030 even though they do not stack as such when put atop a ball offer a good pattern out to 15 yds or more, I don't know about such restrictions in other states that might infuence what one uses.