Using such high explosive would apparently have an effect akin to having a rail gun that fires in all directions.
This is not something you would use for anti-personal, it is extreme overkill.
Fragmentation mines, even way back WWII, were down right deadly.
This includes the good old 'bouncing betty', which is a good example of an explosive surrounded by ball bearings.
German S-Mine6 ounces of TNT and surrounded by 360 steel ball bearings, it had a lethal radius of 22 yards (20m), and an casualty radius of 110 yards (100m).
This means if you were standing at the end zone of a football field, and one went off in the other end zone, you will be close enough to be in a world of hurt if any of the fragments hit you.
Claymores have similar capabilities, even though they are made to have a defined area of effect.
Claymore MineJust as nasty, if you are within 55 yards, you will be hit. Also mentions the velocity of the fragments are 4,000ft/1,200m per second. That's roughly mach 4. There is mention of a casualty radius of upwards of 110 yards/100m, and that the fragments can actually travel upwards of 820ft/250m from the claymore.
Back to the subject at hand.
Upgrading this to MDC explosives, and MDC materials, were are going to end up with a fragmentation weapon that is to a claymore/fragmentation mine as a rail gun is to an SMG.
Also, blast range of explosives likely has no effect on the range of the fragments. Once accelerated, those fragments are going to keep going until they loose their momentum or otherwise hit something.
There will be double damages. One for the explosives themselves, and also for the fragments, which should cover a very large area.
As for the Slammer fragmentation idea, it will be brutal. With a 'slower' and 'longer lasting' blast, it might be possible that the blast will be able to impart more force into the fragments, perhaps making them even more dangerous than if just regular MDC explosive was used.
On a side note, IMO, the fragmentation missiles/bombs in Rifts have a pathetic blast radius.
Seriously, a WWII mine has a kill radius only slightly less than a fragmentation LRM, and a casualty radius several times that of the blast radius of said frag LRM.
Getting a high density metal fragment slammed into you in speeds in excess of mach 4 should hurt a lot, even at a fair distance, especially since the MDC material means they won't simply splatter or shatter when they hit something hard, they will likely deliver a good deal of impact before they are effect by the extreme forces, or simply blast clean through a soft target like a hot rail gun slug through butter.
A basic idea of handling damage and ranges and chance of hitting.
Base damage. 2D6x10+20 MD 10ft radius (explosive blast), 2D6x10 MD fragmentation. (based on the fact the explosive is comparable in power to a high explosive LRM, it should have comparable fragmentation damage also)
At greater ranges, damage should still be possible, with increasing chances of fragment being spread out to the point there are 'gaps' in their coverage.
Normal damage out to normal range (80ft?)
Damage halved again for each range increment, and increased chance to miss until it becomes very weak at 3rd range increment (1/2 and miss on 1-4 on D20 at 81-160ft, 1/4 and miss on 1-8 on D20 at 161-240ft, 1/8 and miss on 1-16 on D20 at 181-320ft).
Double damage at 'point blank' range (10ft or less, on top of explosion damage, extreme pain, likely create a 'cone' behind the point blank target that keeps others protected from fragment damage?)
Fusion Blocks and fragmentation.
Should work as well as using a flamethrower to propel a stick of butter at a mutant lobster... that is, there won't be anything left to inflict fragmentation damage, it will just add some more superheated matter to the mix.
In regards to DU fragments.
Not going to work well with high explosive, IIRC, DU has a habit of fragmenting (and igniting) when it comes to major impacts.
A concusion/shockwave type weapon like a Slammer (or a thermobaric charge) could possible be more 'gentle' enough to make it more possible.
On a similar note, Stirling Silver, it is stll 97% silver (give or take 1-2%), but is far harder, so it could be a possible usable material also.
Or to mess with Elementals, pure iron with magic to make the iron fragments MDC.