Yes, up until 6 months ago(ish?) Tulaammo looked like it was copper jacketed, yet if you took and house key a scraped it the copper would come off. Now it looks steel and has a transparent coating on it - no idea what the coating is.
The copper color was just "washed" on copper that would lightly plate it, imo doing nothing except confusing consumers.
Real copper jackets provide three benefits, maybe more:
1. Allow the projectile to really "bite" into the bore of the barrel so that the twist rate effects the projectile as the manufacture intended.
2. Copper Is softer than the CHF barrels, which allows the barrel to get hot from sustained fire without being damaged by a cold steel (cold means harder because it's not hot) projectile.
3. Damage on target. Copper jackets fragment on impact causing more damage than a projectile that just goes straight through.
All of this being said certain things should be taken into account, most people with with semi auto rifles will never shoot a rifle enough to wear out a barrel, especially if you have multiple rifles that you shoot. I've seen a hand full of studies similar to the one I posted and barrels run bimetal projectiles fine if the gun is allowed to cool. And then cost, idk what it cost to rebarrel and HK now, maybe 700-1000 bucks? Well if you can shoot 10-15k(likely more in semi auto) rounds before rebarreling the rifle, saving $100+ per 1000rds then you still come out on top by shooting the bimetal steel stuff.
Personally I run my belt fed with the Russian stuff because I can change the barrels myself and the $500 is easily off set by the savings on ammo. (1919 and a Shrike to be specific). I runs mix through my clones based on what ammo I have available to me and I only run copper jacketed ammo through my real HK because I do want to replace the original barrels.
As for the Sparks on the back stop, I'm not sure. I would think that's normal with any real copper jacketed steel core ammo. But idk, I really only shoot outside.
Also no idea how polygonal barrels wear, I've never seen anything about that. But I've run 4-5k of .45 Tulaammo through my glock 21 with a polygonal barrel and it's still dead on.
That's my opinion, based on the studies I've read, personal experience with HK's other rifles and belt feeds.
Is this why the first box of tula 9mm I bought to try out had normal copper-colored bullets, but the case of 1000 I ordered later are silver? Or do they actually make some copper jacketed stuff? I don't remember the kind of sparks I see now on the backstop being thrown with that first box. But maybe I just wasn't paying attention.
Is the wear from bi-metal jackets any better on polygonal barrels? Now I'm worried about sending the rest of that case through my VP9 or P30sk...