[masraum]

If you all believe wikipedia for a more modern grenade.

The M67 grenade has a spheroidal steel body that contains 6.5 oz (180 g) of composition B explosive. The M67 grenade weighs 14 oz (400 g) in total.

The M67 can be thrown 30 to 35 metres (98 to 115 ft) by the average male soldier.[citation needed] Its fuse delays detonation between 4 and 5 seconds after the spoon is released. Steel fragments (not to be confused with shrapnel) are provided by the grenade body and produce an injury radius of 15 metres (49 ft), with a fatality radius of 5 metres (16 ft), though some fragments can disperse as far out as 250 metres (820 ft).[4]

There's less info on wikipedia about the old "pineapple" style grenade.

total weight - About 1 lb 5 oz (600 g) depending upon filling

the explosive filling, either 1.85 oz (52 g) of TNT, 2.33 oz (66 g) of Trojan explosive (a mixture of 40% nitrostarch, ammonium nitrate, and sodium nitrate), 1.85 oz (52 g) of a 50/50 amatol/nitrostarch mixture, or 1.85 oz (52 g) of Grenite (a mixture of 95% nitrostarch and binders). Some early Mk 2 grenades were filled with 0.74 oz (21 g) of smokeless EC powder. The improved "Mk 2A1" (a designation used informally by armorers, historians, and collectors, but never by the US military[3]) introduced in 1942 was filled through the fuse well instead. The Mk 2A1 was initially filled with 0.74 oz (21 g) of EC powder. In 1944, the EC powder filling was replaced with 1.85 oz (52 g) of TNT.

I found some random dude that posted the following.

But what makes grenade shrapnel so deadly is the speed with which it is dispersed. No shotgun round could match the burn velocity of the average frag grenade’s charge. Grenade shrapnel also has a good bit of kinetic energy from the velocity that the shotgun charge could not create. Not only create, but the maximum pressure a shotgun could withstand is magnitudes below the brief pressures generated within the average frag grenade. The US M67 frag uses Composition B as its ‘filler’ (explosive). This is the same filling in US Howitzer HE artillery shells. Composition B is a binary explosive, using 59.5% RDX and 39.4% TNT actives and is stabilized by parrafin wax. RDX detonates at 8,750 meters per second; TNT, 6,900. They detonate at the combined velocity of 8,050 mps, or about 24,000 feet per second. That means the blast wave, the expanding combustion gases, and the flame front (small) are moving at about 4–3/4 miles per second. A good .30-’06 bullet moves out at about 2,500 fps or about a half-mile per second. The grenade charge is thus in practicality about 10X as forceful. This velocity, combined with the intense pressure it creates just prior to the grenade body disintegrating, propels fragments outward at about 5,000 fps briefly, before air resistance to the irregular shaped shrapnel causes rapid deceleration. Grenade frags can travel about 600 feet, but are usually lethal only out to about 150 feet.

A good shotgun load pushes the ballistic mass out of the barrel at about 1200–1400 fps. It develops a chamber pressure of about 11,500psi. That’s why shotguns are not machined as heavy as rifles (.30-’06 generates up to 48,000psi and the barrels and receivers look much heavier and thicker along their entire length than in shotguns). You can fire a shotgun with the sun behind you and even see the slow-poke shot in flight.

Additionally, modern frags are not your Granddaddy’s ‘pineapple’ grenade—the shell is thinner and the ‘shrapnel’ is a packing of various materials inside the grenade. Most of these materials (including pieces of wire) would fly poorly at the snail’s pace a puny shotgun charge could push them. Firing grenade fragments through a shotgun with a max-pressure shotgun load would most likely not result in a more lethal shotgun round, but probably a lesser one.

So if you’re positing a shotgun as your primary weapon, it would be far better to fire 12-ga 00-buck from 3 or 3–1/2 inch magnum shells.

I found some interesting photos.