BlackBart,
Here's a post I made not long ago involving this subject, on a thread that started about Speer Hot-Cor bullets, but eventually involved Federal Fusion bullets and Speer Deep Curls, both which are made by Speer using the same process:
"Eventually Federal Fusion ammo became so popular Speer decided to introduce the bullets as handloading components. But the marketing whiz then at Speer decided they needed a different, spiffy name--which was really odd because "Fusion" was already widely recognized among hunters. A lot of people thought the new Speers should be called Fusion bullets to take advantage of that fact, but the marketing whiz insisted, and came up with the Deep Curl name. Deep Curls were also going to cost just about the same as Hot-Cors, and were supposed to replace Hot-Cors. But for quite a while very few Deep Curls or Hot-Cors were available--and when Deep Curls did become more available, they cost significantly more. Apparently so many hunters refused to buy Deep Curls (instead switching to Interlocks or other relatively inexpensive hunting bullets) that Speer decided to drop 'em and start making Hot-Cors again."
I'll add that yes, Deep Curls did result in higher pressures than Hot-Cors, which is why Speer often introduced a Deep Curl of slightly different weight than the "equivalent" Hot-Cor, to avoid the problem of shooters just switching bullets and using the same powder charge. But in other calibers they introduced the same weights, especially traditional weights like 1560 and 165 in .30 caliber, which probably resulted in pressure problems when the same powder charges were used.
In answer to your last question, I personally don't think Deep Curls offered anything over Hot-Cors for hunting whitetails. A good illustration is the 165-grain .30 caliber Hot-Cor I used to kill an average whitetail buck in the 1970's. Muzzle velocity was around 2800 fps and the buck was running away at 100 yards, angling just enough for a bullet to slide into the rear of the left-side ribs. At the shot he stumbled a little ways and fell, and I found the bullet perfectly mushroomed in the right shoulder, retaining 85% (that is not a misprint) of its weight.
I dunno how a Deep Curl could have done any better--but that is also far from the only Hot-Cor I've used on deer. They've ranged in size from the 105-grain 6mm to the 200-grain .338, including some 140 6.5mm's shot from the .264 Winchester Magnum at 3200 fps. All worked just fine.
