Ole said it again, remaining silent likely would save me from embarassment, but here a new try to entertain you all.
The whole is headlined as “steel ammo” (besides that being wrong terminology as is known, and “steel cased ammo” further down in the text makes it almost worse) what is missleading since this here is a test of different brands using soft steel jackets. In my view 2 different things.
Going by the headline and soft steel jacketed projectiles (terminology!) I would have expected that exactly all components in the test were identical but the projectiles in question.
Means same case, primer and propellant and as Jochem said same guns and there in particular same barrel material.
Only then a conclusion on what is ruining a gun can be done. In particular as propellant is not less important in this issue and as we see every cartridge tested came with a different propellant.
I am almost sure there is test reports (by the US military, available on DTIC maybe?) which have evaluated this in a scientific way as the issue must have been on the minds of generations of engineers.
I am not questioning the findings in this report at all but more the framework and technical approach.
And there must be many factors in all this which went unobserved in the report above since it is also known that there is large caliber projectiles with sintered iron driving bands which caused less barrel wear than copper bands.
Just my opinion.