That's a beautiful gun, ejector and I see pins so not a droplock. Single or double trigger? Westley's aren't that hard to figure out. Explora = 2 1/2" cartridge 730gr @ 1250 but with a capped bullet. It should regulate with a lead paradox style bullet to 50 and 100yds but might need some tweaking. Do you have bore and choke measurements? The gun looks to be pristine. The Holland ammo may be too slow to shoot well in your gun but it is worth a try. There are no capped bullets commercially available. Don't use modern slugs of any kind in this gun they are too hard. The cap doesn't really contact the choke.
I have a gun that shoots the capped bullet also, send me a pm.
A capped bullet should have a tighter grouping and better ballistics. Pretty impressive for a " ball and
shotgun"
