I have a Lefever 10ga E grade ca 1889 with 3" chambers & also a post 1907 Lefever 16ga H grade with 3" chambers as well. I can't of course vouch that either left the factory with that length chamber, but as shells were available in those lengths to order at the time of build & would not be many years hence till they would become unavailable in either of those gauges the logical explanation is they were ordered that way.
Researher;
I only have a very meager collection of old shells but am almost certain I have some old factory paper 10 ga shells which are shorter than 2 7/8", probably 2 5/8". I will have to get them out & see what I have. I can of course only measure the loaded length, but can determine very close to what the fired length would be.
