This is a standard trope in warfare lore. Would this actually muffle the explosion enough to prevent anyone nearby from being killed, or would serious injury or death still occur to bystanders within, say, a 10-foot radius?
Previous thread:
Grenades kill and wound primarily through fragmentation, not through the blast itself. A properly dug fighting hole will include a grenade sump for that reason. Myth Busters testedthis, and determined that a soldier throwing himself on a grenade would reduce injury to bystanders.
Yes, it does work to smother the grenade and it is even possible to survive the blast.
Let Jack Lucas (Genuine Billy Badass) and youngest Marine to ever receive the Congressional Medal of Honor, tell how he smothered two at the same time.
Here’s the citation:
The President of the United States takes pleasure in presenting the MEDAL OF HONOR to
PRIVATE FIRST CLASS JACKLYN H. LUCAS
UNITED STATES MARINE CORPS RESERVE
for service as set forth in the following CITATION:
For conspicuous gallantry and intrepidity at the risk of his life above and beyond the call of duty while serving with the First Battalion, Twenty-sixth Marines, Fifth Marine Division, during action against enemy Japanese forces on Iwo Jima, Volcano Islands 20 February 1945. While creeping through a treacherous, twisting ravine which ran in close proximity to a fluid and uncertain front line on D-plus+1 Day, Private First Class Lucas and three other men were suddenly ambushed by a hostile patrol which savagely attacked with rifle fire and grenades. Quick to act when the lives of the small group were endangered by two grenades which landed directly in front of them, Private First Class Lucas unhesitatingly hurled himself over his comrades upon one grenade and pulled the other one under him, absorbing the whole blasting force of the explosions in his own body in order to shield his companions from the concussion and murderous flying fragments. By his inspiring action and valiant spirit of self-sacrifice, he not only protected his comrades from certain injury or possible death, but also enabled them to rout the Japanese patrol and continue the advance. His exceptionally courageous initiative and loyalty reflect the highest credit upon Private First Class Lucas and the United States Naval Service.
More Billy Badass than the rest of the world.
The common misrepresentation in movies is that a grenade creates a huge blast, destroying buildings, blowing out doors and hurling bodies in every direction. It’s complete nonsense, of course, as it’s an antipersonnel weapon (as mentioned above). The idea behind such a thing is to wound as many as possible, requiring the assistance of healthy troops to tend to and carry the wounded, thus removing them from battle. While grenades can kill, they’re generally not designed for that purpose.
Here’s a picture of him afterward. 
Read also of Matthew Croucher GC who put his rucksack on the grenade, winning the George Cross in the process.
I’m a bit stunned he wasn’t awarded the Victoria Cross. It seems cutting it a bit thin and bureaucratic that “no enemy was present”.
PFC Ross McGinnis threw himself on a grenade inside his HMMWV. All suffered some injuries although the medic riding with them only had ruptured ear drums and a concussion. One was knocked unconcious briefly and had minor wounds; he got out was able to keep fighting after he regained consciousness. The two on the left side of the vehicle (driver and the SM seated behind him both) took shrapnel wounds.
That’s a grenade going off inside a contained metal box. 2 of 4 avoided serious shrapnel injuries and were able to keep functioning. It’s not hard to expect far worse results if PFC McGinniss had followed the battle drill and left the vehicle through his hatch.
Beat me to that one. Threw himself on the grenade, lived, and refused to be evacuated afterwards. A giant brass pair and the brains to operate outside the film trope.
Hey, don’t sell the guy short – he was wearing the rucksack at the time. 
I was interested to hear him say, in an interview, that he did expect to survive the blast. He thought he might lose an arm or a leg, but he trusted his body armour to protect his vital organs.
The GC and the VC are of equal status, and the GC is what’s awarded in situations involving armaments left lying around (e.g., bomb disposal personnel).
Not so: the VC takes precedence if someone has both.
I’m surprised anyone would question the reality of such acts of sacrifice. Granted its a rare event but Wikipedia lists quite a few. I recall a New Zealand Army sergeant many years ago throwing himself on a live grenade dropped by a nervous soldier. He died. I think he was awarded the Military Medal posthumously but can’t find a reference.
A Victoria Cross is a step up - usually the act of bravery involves saving a group of soldiers. Such as single handedly entering a pillbox or a machinegun emplacement. Equivalent to the Medal of Honour.
True, although nobody ever has been awarded both. There is a unique instance of a GC recipient and a VC recipient in the same family.
There is also (you learn something new every day) one instance of a man receiving a VC for saving the life of his brother who already had a VC.
Was it this guy?
What Quartz said; and Matthew Croucher GC wasn’t involved in ordnance disposal, he had set off a trip-wire and acted to save the other members of his reconnaissance patrol in Afghanistan and was initially put forward for the VC. While technically it is correct that no Taliban were present when he tripped it, like I said it seems overly bureaucratic. He insisted on remaining with the patrol which set up to ambush Taliban coming to investigate the sound rather than be evacuated. In the event, no Taliban came to investigate it, but if they had and a massive firefight ensued the same logic could be applied that no enemy was technically present at the moment of Croucher’s action.
Well, he had to have one heck of a sack to haul around those big, brass…
Wait, you said “ruck”? Never mind.
I recall reading an article on this subject (haven’t been able to track it down) that stated as the explosion from a grenade tends to travel mostly up and outwards if soldiers nearby simply threw themselves flat on the ground they could avoid much of the danger.
The point of the article was that people, and by extension soldiers, have unrealistic ideas about the effects of grenades and that they have been throwing themselves onto them to save others unneccesarily.
No idea if thats true or not but I thought it was interesting.