Quote Originally Posted by u-b View Post
Okay, we got no more responses on GURPS rules forums, but from the three we got basically no one recommends using B409 rule with multi-ball ammunition as it was neither designed nor intended for that. What we can do instead is...
1. Just ignore it and keep the rest as is.
2. Nerf things a bit as per HT172 multiple-projectile loads damage formula instead of the more specific HT173 multi-ball damage values, which gives us 5d+1 instead of 6d+1, AND/OR...
3. Nerf things a bit by treating shots under 50 yards to be equivalent to solid slugs, doing 7d+1 instead of two separate projectiles.

I'm fine with any combination of the above.
For now, option 1.
We can come back and rethink things later.