.177 slugs - why no diameter size options?

Every other caliber has a bunch of size options to try out in different barrels. Why wouldn’t .177 be the same?

My 177 Alpha Wolf shoots 4.50mm H&N pellets better than 4.52mm ones. My luck with off the shelf slugs hasn’t been too good and I wonder if this might be why.

NSA 177s are listed as .178. Howlers are listed as ‘caliber 177’, but they are made by NSA so I think they would .178 too. H&N’s new slugs say .177 caliber as well with no mention of the exact diameter.

It would be nice to be able to try .176, .177, .178 in my Alpha to see if I can find a better working slugs.
 
Every other caliber has a bunch of size options to try out in different barrels. Why wouldn’t .177 be the same?

My 177 Alpha Wolf shoots 4.50mm H&N pellets better than 4.52mm ones. My luck with off the shelf slugs hasn’t been too good and I wonder if this might be why.

NSA 177s are listed as .178. Howlers are listed as ‘caliber 177’, but they are made by NSA so I think they would .178 too. H&N’s new slugs say .177 caliber as well with no mention of the exact diameter.

It would be nice to be able to try .176, .177, .178 in my Alpha to see if I can find a better working slugs.
Our Slugs are .1775 / 4.51 mm. This diameter actually worked best for all of our test guns.

Best regards

Jörg