"Certainly, it is the rifle round. "Ordinary" or not, doesn't matter. Tell me what is the criterion for division? Case length? Muzzle velocity? Muzzle energy?"
Intended role. It is to bridge the gap between 800m and 1200m where the .308 lacks range and power, but 50 cal rifles are too big/expensive/powerful for the role.
"Nice try, GazB, to compare weight battle rifles without optical sights to assault rifle with them. I show You the L85A1 weight without SUSAT with iron sights. So, add about 0,5kg (optical sight) to all battle rifles weight and than once again try to compare weight. "
I included the weight of the scope for waepons that carry scopes as standard. Hence the SA-80 and the SVD weights include scopes.
"That was the first assault rifle. Compare the first SMG weight to modern ones. "
So we then establish weight as being immaterial in the definition then?
"Nope. Take a look at 12,7mm (.50) HMG also may be used as infantry fire support weapon on wheeled mount or as vehicle weapon mounted in turrets (e.g. HMMWV, M113). Also used in single or double AA mounts. So, Browning is also automatic cannon? The cannon vs. machine guns calibre limit is 20mm not "over 12,7mm". And that's not "my" opinion, they are HMGs by definition - open JANE's Infantry Weapons and check - 14,5mm KPV and 15mm FN MILO are considered as HMGs. "
As I have mentioned the division is defined as shell projectiles. In the past that meant 20mm. Now such a definition could include HMGs through the improvements in power in HE charges and design of shells.
"As I said 20mm is upper limit for rifle ammo, so some of 20mm round are (or may be) and some aren't rifle cartridges. "
So you can't talk about a Rifle or Cannon "calibre" if that calibre can be the same. (ie .308 is a rifle calibre, but if 20mm is both a rifle calibre and a cannon calibre then it is neither and both.)
"You're right. My fault, sorry."
No need to appologise, from your location I am guessing English is not your first language. With this in mind misunderstandings are natural, though your English is excellent BTW.
"This kind of shotguns have their own name - "slugsters". "
An American term... though you will notice my term is more accurate in that it is obvious that the weapon is a rifled weapon. I have a smoothbore shotgun with a cylinder bore (ie no choke) which I use to fire Slugs and could call it a slugster too. (it has rifle type sights especially for firing slugs).
"...also 20mm Croatian RT-20 and 20mm Finnish APH-20."
Would be interested in hearing more about them if you have any links...