Regardless of what word he used, he's describing the bolt bouncing off the rear of the receiver, adding a bit more power to the bolts forward stroke then spring power alone. 

Does the PKM pull mechanism shorten the total length by several inches?

yes, as it allows placing the belt feed unit above the barrel breech

Just look atthe Polish UKM-2000 machine gun which is, basically, the PKM mated to MG-42 belt feed

gatnerd said:

Regardless of what word he used, he's describing the bolt bouncing off the rear of the receiver, adding a bit more power to the bolts forward stroke then spring power alone. 

Some buffers can also add power to the forward stroke.  A spring type can prevent solid impact with the rear of the receiver,  if it is not fully compacted at the end of the bolt's travel, then use the stored energy to accelerate the bolt forward.  The amount of energy returned to the bolt would likely be higher than if it had impacted the rear receiver.   A hydraulic buffer can also return energy for forward bolt motion, although by design, a certain fraction of the energy has been absorbed.  Nevertheless, since a hydraulic buffer, like an automotive shock absorber system, can be combined with springs and valved for relatively high damping in compression and low damping in "rebound",  it can return a significant amount of energy to accelerate the bolt back to its original position.

Yeah that one, I'm not an engineer I just play one on tv lol.

I'd love to be better educated than I currently am, working on it but there's so mucg to work on so little time.

What baffles me about that is both the Chinese and arsenal Inc can and do make rimless pull feed 308 pkm's. 

There's even ways to do that with a disintegrating link, and the impetus to do so since NATO/American standard push through links aren't all that light efficient or otherwise favorable.

It makes much more sense to me to just keep the pull feed and design a better cheaper and lighter disintegrating link

Are you an actor IRL?

Lol no, I did some PA work on tv shows long ago but I'm definitely not an actor.

I'm just an eccentric gun nerd who likes to tinker in his basement ...

I used to want to be something more but recently I've decided there are worse things to be than me.

Fired 6.56 mm and 7.62 mm Evolys today. Hugely impressed.

Did FN UK give any information on future developments in their rifle range - will we see a ‘new’ SCAR variant ( apart from the NRCH ) ?

 I got some hands on at DSEI of Evolys and also was impressed with it , crazy light in the 7.62 version yet solid feel .

what did the British Army guys think ?