"...a 45 gr sp should be more than capable of taking a deer..." Not in a million years. That is a varmint bullet and is totally unsuitable for deer sized game.
"...I can't see how a SP or a TSX in the boiler room..." They're varmint bullets too and will not penetrate enough to get to a boiler room or even the captain's bath room.
That's hilarious, another spewing of the same old same old, that shows that you don't actually have any experience about which you speak so authoritatively.
FWIW, I recovered 37 grains of a 50 grain spire point from a Mule deer doe this last month, the bullet traveled in through the ribs, destroyed two lungs and the top off the heart, exited through the ribs on the far side, and the remains of the (well mangled by now) bullet, were found against the bone on the leg opposite where it was shot.
So much for that theory.
I also helped out a newb hunter, who had shoulder issues, and was somewhat recoil adverse as a result, to gut her very first deer, also a Mulie doe, shot with .223 factory ammo, couldn't tell ya if it was 50 or 55 grain spire points.
The heart on that one was destroyed, not just a little bit, but "leave it on the pile" destroyed, and the base of the bullet was found against the off side rib. Total dump of energy between the ribs. Perfect!
5 grains extra or less weight isn't going to make a whit of difference to the deer. Choosing the correct and appropriate shot, to suit the cartridge in use, will. In both cases, the entry was through the ribs, behind the point of the elbow, and 1/3 of the way up.
I worked with one dolt that shot a moose in the arse with a 7mm STW and stood slack-jawed and watched it walk off into the swamp. He thought that his super-magnum should have killed it outright. I am sure the moose died, eventually. The lot he hung with were the sort that thought getting liquored and shooting holes in the other guy's boots drying by the fire, was "good times" though.
Too many people have made up their minds based on what they think they know, rather than what they actually know. They will often share, when sometimes it would be best if, well, they just didn't.
Oh yeah. Look up a TSX bullet. not exactly meant for varminting. That is the bullet I WOULD choose, if I wished to use my .223 as a general purpose gun, as like as not, whatever angle I shot a deer at, that one would come out the far side, or darn close to that.
Cheers
Trev