Like you said bullet design has alot to do with it also.
Shot the 123 hornady Sst
50rd bxs
Accurate
Pricey
Lotta euro brass case and copper jacket bullets versus bimetal jackets out their also that are accurate.
S&B
Privi
Yugo M67
Others also..
Accurate but pricey.
I think aotta the hardness of bimetal jackets in relation to rifling is like a mouldablity issue to them kinda skipping longitudinal across lands.
Espeically in the leade area and 1st inch or 2 of the rifling before taking "hold" for spin.
Kinda conjecture my part.
But I have looked at alot of ak,s and akm,s where they leade is not a nice visible ring and it looks basically like a overly long shotgun forcing cone going into the rifling.
Some look relatively VG exterior and mech wise.
Then ya look down the barrel.....
Not cleaning , running too hot and mag dumps can do this also.
I think bimetal plays into it also as a factor.
But cleaning alleviates bi metal barrel wear issues IMO.
# of factors come into play.
Build up of and erosion issues of bimetal can be addresed
And then ya throw corrosive ammo issues into also.
Perfectly good wpn neglected is no longer a perfectly good wpn.
You can deliberately screw up and destroy just about any mil type wpn firing a obscene amount of ammo thru it in a short given time.
Tracers rds are the worst and take the least.
Reemed out many an azz over the years, soldiers trying to do the full tracer mag thing mag after mag after mag auto and semi...
Just cause they thought it would be cool and could get away with it.
🤦♂️🤦♂️🤦♂️🤦♂️
Only person in a platoon with more than a 4 to 1 ratio should be the wpns squad leader.
Full 30 for intial mag to desg tgts to his guns.
Then 2 to 1 rest of his mags guns know its him desg tgts and the line sqds from his firing sig.
Everyone else on 4 to 1 if needed, top 2 tracer with last 3 to sig your getting close to reload.
