I agree with you as my engineering exprrience tells me the same. Lets look at it this way. SAAMI specifications for a .308 barrel is a bore diameter of .300 and a groove diameter of .308 meaning the rifling is .004 in height (.300 plus .004 X 2 equals .308cal). Now projectiles for this cal are usually around .3090 minus up to .0030 and they do vary quite a bit based on the thousands of rounds that I have loaded over the years.
Now take into condideration that all projectiles are going to deform to the barrel unless the projectile is made of harder steel than the barrel. This deformation is what causes the projectile to engage the rifling making the projectile spin or rotate if you prefer. If the projectile is harder than the barrel, the gun will explode because the .308 projectile will not deform to the .300 cal barrel. You also have to remember that the barrel DOES NOT remain static during the firing process. Heat and pressure will allow the bore to grow in diameter. This is why a cold barrel will be more accurate than a hot barrel.
So the issue is the deformation of the projectile. I submit that whether the projectile is copper washed, copper clad bimetal or copper jacketed, due to the deformation there will always be copper engaging the rifling as the projectile initially starts its travel down the barrel. Here is the potential issue. Will the copper clad, copper washed, or copper jacketed projectile survive the entire travel down the barrel with sufficient copper intact gliding along the grooves and bore (rifling) before the friction obliterates the copper around the projectile.
What I can say is that so far, every copper jacketed and copper clad bimetal projectile that I have recovered intact, the copper jacket has survived intact. Allbeit, I do not make a habbit of recovering many fired projectiles though.
There are a multitude of variables that have to be examined and emperical evidence indicates that there is minimal additional wear caused to the barrel when a bimetal projectile is sent down the barrel ONLY if the jacket does not remain intact.
I think an argument can be made on both sides but unless a thourough examination is made we will have to decide for ourselves whether it is bad to shoot a specific ammo or not.
As I indicated, I do not do FA fire nor do I do rapid fire so the bimetal rounds that I choose to use do not affect the barrel in any significant way to cause me any concern as the barrels of my firearms will outlast me in the longevity arena.
Your firearm, your choice. JMHO.
By magnetic you mean, if you hold a powerful magnet near a bullet you'll get a reaction, cause my lake city M80 didn't move at all, and it was a serious magnetAll U.S. M80 ball is magnetic. all US and Greek M2 (.30-06 ball) is magnetic. At least all I've ever tried.
My opinion? Shoot it (if your club allows it).
Interesting. Try touching the bullet to the magnet and see if it sticks. My Lake City M80 definitely does stick to a magnet. One of those telescoping pen-type magnets.By magnetic you mean, if you hold a powerful magnet near a bullet you'll get a reaction, cause my lake city M80 didn't move at all, and it was a serious magnet
Note: This product contains steel in the projectile (this bullet is magnetic) as it is made to military XM80C specifications.