This has been covered many times in the past at the Campfire. A search will give you lots of info.
To summarize: I started using the Nosler .284" 120-grain Ballistic Tip several years ago. A friend of mine who worked at Nosler at the time told me that the bullet was a total flop with varmint hunters (duhhhhh ), but that the rifle metal silhouette shooters used a zillion of them.
Nosler got complaints from the rifle silhouette shooters because the bullet was too frangible to consistently tip over the 500 meter ram. Because the rifle silhouette use was seemingly the only market for the 7-120, Nosler made the jacket considerably heavier than the original design.
This change was intended to satisfy the silhouette shooters complaints, but an inintended consequence was that they unwittingly made one heck of a big game bullet.
The first I heard of it was my friend at Nosler was shooting California wild boars through both shoulders (both gristle plates) with the 120 in a 7-08. Full penetration and very dead pigs!!!
Please bear in mind that the silhouette story above is purely legend, but if you will split a 7-120, you will find the jacket is waaaay heavy. Actually, it resembles the .338 BTs, which are heavy and are sure killers on larger critters.
Down to your question, "What has Dogzapper shot with the 120s?" Answer: A bit of stuff.
I've killed a couple of 6X6 bull elk. Not big ones, but around 290 B&C and decent bodies for five year olds. One was shot from above, looking away at 375 yards, the bullet entered the spine behind the shoulder and was found under the hide of the chest. Expanded to .75" or so and the recovered bullet weighs about 100 grains (it's around here someplace and it's a big lead and copper ball.
Second bull was 400ish. Not to be fancy, I shot the bull through the center of the shoulder. The bullet broke both shouders and was recovered under the far hide. The bullet is identical to the first bull's bullet.
Both of these were killed with the 7-08 Ackley.
Other kills with the gun and bullet were a large Montana mule buck at way too close, peeking though a juniper tree at first light. Horns were big and so was he and I had to hit the only open thing I could see ... an eyeball. And I did.
Bullet went clear through the head and didn't break the skull. Exited leaving a one-inch hole.
Another Montana mulie was probably the largest-bodied mule I've ever shot in Montana. He was aged at 9 1/2 years in Great Falls game stop (by a PhD professor of big game). I knew the buck intimately and had not been able to kill him the three previous years. I caught him in a herd of over 100 does, with head low and his dick hanging out. Saw him at over 400 yards in the dusk and made a running open field stalk ... closed to 205 yards and shot him a little too high behind the shoulder. Spined him, dead right there, bullet fully penetrated leaving a 2" exit.
There's a few more deer with the 7-08 and some antelope, but the tale is always the same.
I've also used the 120 in the .280 Ackley @ 3,370 fps.
Shot a moose one morning with it. Range was 91 yards and the three year old dumbly stood in the middle of a farm two-track. I shot him under the chin, slightly to my right, trying to break the spine upon exit. One or both carotids were broken, C-2 vertabrae was totally missing and the bullet exited leaving a two-inch hole. For all I know, it may still be in low orbit of the earth.
Mickey Moose died right there.
I've shot many antelope with the bullet in the .280 Ackley. Ranges from 100 to over 500 yards. Nver missed a got with it and never shot twice. Total penetration from most any angle, except for one old and large buck that I shot fully in the chest and recovered the bullet (deadliest mushroom in the woods) right next to his bunghole. I guess you'd call it full-penetration of a goat, minus one-eighth inch.
Lotsa mule deer and whitetails. Normally full penetration. Don't remember ever recovering a bullet from a deer. Exits usually rin one to two inches.
You ask about maximum recommended impact velocity on deer and elk. Heck I don't know, I just go out there and kill stuff.
I don't know that I'd recommend it on elk of moose. I have a habit of hunting deer with the tags for big critters also in my pocket. I carry 120s and sometimes magic happens. If I was purposely hunting elk or mooses only, I'd probably up-bullet to a 139 Hornady Interlocked in both the 7SGLC and the .280 Ackely.
Or for really big stuff, like the Asian water buffalo I killed a couple of years ago, I used the 154 Hornady Interlocked in my .280. I severed both carotids and created a buffalo blood fountain that was quite beautiful.
Anyway, I've written way too much. Use it or don't, it's not a matter of honor or pride. I use the 120 and am not prejudiced and find it kills the schit out of stuff without ruining a lot of meat.
In truth, the 120 Ballistic is considerably "harder" and in my experience will out-penetrate the 140 Ballistic Tip.
I also find the 139 Hornady Interlocked (plain, cheap cup-n-core) to be one heck of a great bullet.
Those of us who love medium sized 7mm cartridges are truly blessed with a plethora of excellent big game bullets.
Steve