Absolutely correct
Longwalker!
DGX (X for "expanding") and DGS (S for "solid") are designed to shoot to the same point of aim but are two vastly different bullets. The pair is designed to provide the choice between expansion in soft tissues (e.g. double lung & heart shot from the side) and deep penetration through any bone structure (e.g. shoulder or brain shot on elephant, of "any-angle" follow up shot on heavies (Elephant, Hippo, Buffalo) running away from a non-lethal first shot). The DGX was indeed replaced by the DGX B (B for "bonded") that has earned to approval of Kevin "doctari" Robertson, the well know Zimbabwean veterinarian and PH. No faint praise!
I have had good results with it in .470 NE on Buff...
As to the advice given by some folks against using FMJ, I shall respectfully disagree.
Sure,
Rare Breed, the monometal bullets are all the rage right now and the fashionable kids on the block, but they are not without their own challenges... the classic dilemma being to have them hard enough to not bend, but still malleable enough to not wipe out the rifling in the barrel, or crack the solder joint of the barrels on double rifles. A large number of designs have been gone through from what were generally groove calibers slugs in the beginning, to bore riders or semi-bore riders with stabilizing bands to take the rifling; and what was typically naval bronze initially (too hard!), to a collection of pure copper, brass, or various mixes of gilding material and softer bronzes. It seems that they have come to maturity now, and they certainly are good bullets...
But they do not kill any better than best quality (emphasis: best quality) jacketed solids such as produced by Woodleigh for example, or for that matter Hornady whose DGS has a rather good record in Africa.
So, yes, the monos are the latest evolution of "solids", and are indeed technically true solids, but that does not necessarily make obsolete the traditional jacketed slugs designed to be "solid" in the traditional understanding of the word in the context of African hunting. One advantage they retain is that they do not need to be as long as the monos to get to the proper weight because their lead core is typically heavier, and they have generally been designed to match the older Kynoch design so they generally shoot well in double rifles that were regulated with Kynoch...
I think that ChrisG's first post explains some of the confusion. The term FMJ as applied to military bullets designates bullets which are not designed for Buffalo or Elephant hunting, although cropping officers who used military 7.62x51 loads in their FAL to kill thousands of Elephant and Buffs in Rhodesia in control duties would likely disagree. The confusion comes from the fact that FMJ construction was and is still used (by Woodleigh for example) to designate bullets that ARE designed for deep penetration on DG and that have a much thicker jacket (the Brits used to call them "full patch").
In the context of a forum focused on Africa hunting, the likely understanding of FMJ should not be military FMJ but DG hunting FMJ, which work very well when of proposer design (i.e. jacket thick and tough enough).
As to their use on Buff, I agree with Red Leg. An AFrame or TSX that retains its integrity is a much better choice for Buff in a herd (it dramatically reduces the chances of collateral damage upon pass-through with the first shot). It is the rare PH who still recommends a solid for the first shot at Buff nowadays. The discussion remains open regarding up-the-rump follow-up shots. Solids still make sense because it is a long way to the vital from the tail end, but modern tough "softs" that retain 95%+ of their weight apparently finds their way there, when older cup & core softs that shed 40% to 50% of their weight did not...