The Kord-5.45 is for MVD and police forces, the military are not interested in it because it is too heavy.
PKP is about the same weight, but has heavier but more powerful and longer ranged ammo.
The box and drum only feed RPK-16 is about 4.5kgs and is much lighter but the drums and box mags add weight to ammo... the Kord is about 7.5kg and 7kgs in the newer model and can used drum or box or belt feed, but the RPL-20 is only about 5.5kgs but it can't use box or drum mags.
The Kord 545 looks interesting but is probably too heavy.
In 6x49mm calibre, all three would be useful as LMG because in terms of performance they would actually be better than the PKP in terms of power and range but the ammo would be lighter.
The weight difference is interesting, if we go from the numbers from [url=modernfirearms.net]modernfirearms.net[/url], the weight of the RPK-16 is 4.5kgs, while the weight of the Tokar 2 is given as 7.5kgs, while the RPL-20 is given as between 5.2 and 5.5kgs empty.
Note the Tokar fires from an open bolt only and is full auto only.
For ammo, it says, a spare 300 rounds of 5.45x39mm ammo in magazines weigh between 4.8 and 6 kg (in 30-round box or 95-round drums), while same 300 rounds in steel belts will weigh approximately 3.9 kg.
So 4.8kgs per 300 rounds in 10 x 30 shot mags.
6kgs per 300 rounds in 3 x 95 round drums.
3.9kgs in 3 x 100 round non disintegrating link belts.
Which means each box mag weighs half a kilo, each 95 round drum weighs 2kgs and each 100 round belt weighs 1.3 kgs...
In a unit where you want 1200 rounds of ammo for your LMG carried by your other squad members, that means with drums you will actually be carrying 1140 rounds in 12 drums of 95 rounds, or you can carry 1,200 rounds in 40 x 30 shot mags, or 12 x 100 round belts.
12 drums would be awkward to carry, because they wont fit on chest rigs, and at 24kgs they will be the heaviest option.
40 x 30 round box mags means you will just be taking 30 shot mags from the guys around you and they will weigh 19.2kgs.
With 12 belts of 100 rounds each, the LMG guy could probably carry one on the gun and 3-4 belts on him, so the remaining 7-8 belts could be easily draped over the other squad members who drop them off to his position when you stop or come under fire. Those 12 belts weigh 15.6kgs.
So the lightest the RPK-16 could be with 300 rounds is with 10 x 30 shot mags at 9.3kg, while the Kord 5.45 would be with three belts which would be 11.4kgs, while the RPL-20 with three belts would be 9.4kgs.
At 1200 rounds the RPK-16 with 40 x 30 shot mags is 23.7kgs, the Kord 5.45 would be 23.1kgs, and the RPL-20 would be 21.1kgs.
Obviously spare barrels would effect that too...