Yes, this picture is very strange- the UH-60 Blackhawk cannot lift the M198 howitzer, and  even if it could handle the weight, you need more sling legs.

 

Do you have the explanation?

There are enough odd things in that picture that would make me think that it is a photoshop job.

The perspective of the helicopter and the gun are different, and the sizes seem at odds

There's no apparent downwash effects on the snow-covered ground

The featureless sky would make it very easy to mix two pictures with no obvious join

No ground crew apparent.

Below is a link to the source.  CannonArtillery.com 

 

cannonartillery.com photo gallery 

 

I initially though "photoshop" aswell.  But as neutraliser points out the howitzer is actually still on the ground.

(FALightFighter)

(historynut)  Could it be picking up something else

Yes, I'd agree FALightFighter,
in that it does seem odd to sling-load with only two runners (sling cables connected to lifting hook).

 

If only using 2, as the pic suggests,

the load would be horrible at staying flight-worthy while the chopper is in forward flight: basically, by the pic, the cannon is/was slung at roughly the midpoint, which would leave it teetering like a see-saw, in even the slightest wind (especially if flying forward).

 

Just about every cargo I've seen slung, the sling harness itself does certainly attach to a single point on many helos,

but you need more that two runners, ideally one at each of 4 "corners" of the load, just to generally balance any payload while in flight so it doesn't tilt and buck back and forth.

 

Most slings have the option of a quick-release mechanism to detach the load, but never have I seen some sort of two-point sling attachment on a helo that would allow only one set of runners to be detached (dropped to the ground) yet leave the other two cables remaining in such a way that it puts the load's balance in a precarious situation.

If anything, there's nothing wrong with attaching cables to the midsection of a payload, as this pic suggests,

but one must also then attach an additional sling to each end, ideally of a same length,

just to keep the load from tipping too far in one direction forward or back,

at which point a short sling could cause the load to shift dramatically nose/tail down and risk damaging the load during landing,

or worse,

the load could teeter tail/nose upwards and strike the aircraft...

even if the weights were correct etc... you wouldn't just sling it from the centre either..

 

that piece would be swivelling about like a drunken sailor in a brewery....

Also it seems like a bad idea to hoist a gun by the barrel. You might bend the barrel.

 

And the US army is not cool enough to straigten bent barrels by use of a helicopter, no?