Weapon design - how much can you lighten an artillery barrel?

Going about designing weapons for my TL 8+^ campaign, I'm trying to figure out how much I can lighten the 105mm recoilless rifle, which is pretty similar to the M40 from High Tech. It's a limited production weapon; the Navy only needs to put a compliment of 2-8 weapons shipboard (4-ish on maybe 80 cruisers, a larger number on 80 battleships, smaller number on destroyers and frigates), and enough to equip two marine divisions, which rarely see combat, mostly sitting in garrison scattered between different planets, even during wartime. Even at most 100 weapons a year during wartime is all that would be needed, and if limited stocks are built up during peacetime, it may go in and out of production as the need arrises.



Lightening the tripod is easy - just make it out of the same high strength titanium alloy the navy builds their ships out of, they could likely simply machine it out of scraps from the dockyards, a single cruiser has at least 20,000 tons of the stuff.



My question is how much would using special high strength, but expensive, alloys for the barrel allow you make it lighter? I would assume it's possible, but not actually done today due to cost for a massive number of weapons. The Navy in my campaign enjoys the luxury of having a very small weapon loss rate coupled with a non-expanding number required, so they can afford to spend more per weapon.



So how much, if any weapon experts would like to weigh in. 25%? 50%? I don't really have a number to go on.

Weapon design - how much can you lighten an artillery barrel?