For some reason, 44 cal is actually .429"
10.75 is about .425"
You have to be careful, but it could be a good start. Slug the bores first.
I own a 10.75x45R Heym double, but I have not had a chance to slug the bores yet. I plan on using cut down .410 brass in that gun.
There is a host a variations on those calibers from 10.75x45 from 45mm long case to 52mm and up to 65mm.

I suspect the 45 version will be throwing a 300 grs bullet at ~1300fps. The 52 will be somewhat faster.

Best regards,
WC-