I only use 0,429 diameter bullets and my loading dies are intended for 0,427. Both my 44-40s have 0,429 bores. IF I wanted smallest groups, I probably should get expander plug for 0,429 bullets -- so as to get more consistant alignment of bullets with bore -- at least that is expectation.

I too find loading 44-40 really easy, in spite of thin brass. Maybe I have advantage cause I started loading 32-20 brass when I was 13 years old and still do. One does have to take care in adjusting loading dies, more care than with 44 Mag, 44 SPL, 44 MAG. Lubing is only extra, that is if you are accostumed to using carbide dies.

Stick with lighter loads and 44-40 can be a really pleasant round to shoot. Even with full BP loads and equivalent nitro loads, it is pleasant -- and it will also give you understanding why it was such a popular cartridge for so many, many decades, both in USA and elsewhere.

Niklas