Okay, the RPD and the RPK have the same barrel length, the same muzzle velocity and fire the same round, so how is it possbile for the RPD to have a claimed effective range of 800m while the RPK is only 400m?  What makes this even more interesting is that the effective range of the PK which fires the x54 is only 200m more than the RPD.  Is this due to different standards or what?  
Also, I'm looking at buying an RPD from Vector.  Does it fire from the open bolt or is that still restriced by the F-Toop?  Also, anyone have $0.02 on this weapon?  Thanks!

Quoted: Okay, the RPD and the RPK have the same barrel length, the same muzzle velocity and fire the same round, so how is it possbile for the RPD to have a claimed effective range of 800m while the RPK is only 400m?  What makes this even more interesting is that the effective range of the PK which fires the x54 is only 200m more than the RPD.  Is this due to different standards or what?   Also, I'm looking at buying an RPD from Vector.  Does it fire from the open bolt or is that still restriced by the F-Toop?  Also, anyone have $0.02 on this weapon?  Thanks!

Closed bolt on the semi-autos.  They are sweet rifles.  I highly recommend them.  Vector did a very good job with the RPD.  I also like the blued finish better than the parkerized that Vector uses for their AK's.  I still love their AK's but I prefer a blued or enamel finish.  Copes Distributing is selling the 100 round drum mags including the 100 round belt for $24.99.  Stock up now.  

As far as the effective range, I agree with you that it doesn't make any sense for the RPD to have a longer effective range than the RPK.  

I'm not sure, but I'm seeing the RPK as having a 590mm (23.23") barrel, and the RPD as having a 520mm (20.47") barrel. I'm also see one source say that the RPK and RPK-74 both have 800m max effective ranges. Another source supports what you said about the RPD and having an 800m range.

I have a new Arsenal 7.62 RPK, but have only test fired it to 500m with iron sites. It shot fairly well at that range, especially taking into consideration that I didn't take the time to adjust for windage.

Despite the 800m effective rating, I'm guessing that the RPD and RPK are more like 600m-700m weapons, especially with iron sites. Plus, it's hard enough to see a man size target at that range, let alone 800m.

AK weapons

RPK

RPD

The only thing I can think of is, maybe there's a tripod setup for the RPD with elevation and traverse knobs on it that give it some extra repeatability in sustained fire.

I certainly wouldn't be shooting out to 800 yards with either gun, even in the original full-auto configuration, unless there was, I dunno, a platoon of guys out there moving on line across an open field.  Against a single target?  Shooting any 7.62x39 at 800 yards is just giving away your position for no good reason.

In real life, I'd say 300 is the maximum practical effective range against single targets.  I guess you might hit a fuel truck or something out at 800, so they can claim its within the effective range, but in reality?  Meh.

I think 800 meters might be an effective range if you are going balls to the wall across Europe with thousands of guys blasting away like Mongols on opium.... then it might be effective in some cases.

I almost get a headache just trying to think about shooting out at distance with AK style sights!