I'm curious to hear more details on that long shot with the 6.5 swede. Was it a long day of tracking? Did it require follow up shots?
A typical 140 grain 6.5x55 is producing under 1000 lb-ft at 400m so you'd be pretty close to that limit at 370.
The unalarmed cow elk was slightly quartering to across a large field when I shot her with the 6.5 at 370 yards. (The rifle I has that day as we were out mostly looking for deer, and unexpectedly came across the elk.) Hit her proper height wise, but only got one lung (Was trying to stay clear of the shoulder bone). The rest of the herd was milling about, but did not run off.
She laid down right away, but not flat out. I shot her one more time, again getting the same onside lung. She got up and ran with the herd, about 200 yards to the edge of the brush, and hung up there, as she was having troubles and was reluctant to jump the fence and and leave the field with the herd. I was now closer and gave her one more more shot (do not recall distance, but was probably about 200 yards). This one broke her front shoulder. She jumped the fence but was down about 10 yards beyond. I gave her one last round to finish her when I got to her a few moments later.
My load at the time was the max load of IMR 4350 with the 140 gr Barnes X bullet (Barnes manual of the day (1995). Never chronied the load in my Rem 700 Classic so not sure what the energy would have been at 370 yards. That load would consistently place 5 rounds into just under 1" @ 200 yards, and was just slightly better accuracy wise than the 140 gr Nosler partition load with the max load of IMR4350 in the Nosler manual of the day. I practiced with that rifle and load out to 400 yards on a regular basis (I would shoot about 500-700 rounds per year with that rifle, just practicing, and not including load development, sighting in and hunting).
Previously, I had shot a young bull moose with the 6.5 140 X Bullet combo at about 100 yards. It didn't go anywhere after the first shot and died after the third shot, about 5 yards from where it was first hit.
While bullets all hit vitals, and the one recovered bullet had expanded (shoulder shot on that cow elk), they just didn't seem to kill as quickly as the Nosler Partitions did. I didn't take any more game with the X bullet load after that in the Swede. Went back to Nolsers for hunting with that 6.5x55.
Today, I am shooting the Nosler AccuBond ammo in my LH Sako 85 Hunter. It produces 1/2" groups at 100 yards. At 300 yards it is supposed to have 1435 ft lbs of energy remaining and 1237 ft lbs at 400 yards. Definitely not distances at which I would shoot an elk at today with the 6.5, but I have learned a lot more about hunting elk and ballistics in the 27 years since I shot that cow elk (my second elk overall)!