I have a beautiful .458 WM sporter that I loaded up 300gr hollow points. Was thinking of shooting a deer with it this year. How big an exit hole do you think it will make?

.750 range

I've used 400gr out of a .416 Rigby and you could eat right up to the hole, but 300gr hp out of a .458 could make a mess. What kind of bullet is it? Is it designed for 45/70 velocity?

Standard Hornady 300gr HP's

Probably smaller than a 12 gauge slug.

I considered using my 416 Rigby when I was hunting KY. I was going to go with the 400gr as well. I'm thinking a little stouter bullet in your 458 may help with the destruction issue.

No different than a 20ga sabot.

I would use a 500 grain cast bullet, myself.

2,700 fps vs 1,800 fps... That's a bit different.

It will make about the same size hole as a 454 casuall.

Umm that bullet is meant for the 45/70, and its velocities.  Used on a deer at 458 win velocities, it would be like hunting deer with a varmint bullet.  They say the Hornady 350gr was meant for the 458win, but it doesn't even hold up well at those velocities.  400gr is where you need to look at, and no not the Remington 405gr, that's another 45/70 bullet.  Use the right bullet, it wont make as big of mess as you would expect.  It'll just look like a hole saw bored thru the beast.

actually, I think the 458 will do surprisingly little....  The vast majority of 458 bullets are overwhelmingly designed as stoutly built deep penetrators.  And the impact speeds will be modest.  Penetration could likely be measured in yards and feet, but those bullets won't open up really expansively or explosively.  You'll get a nice 1 inch hole all the way through the deer, then thru the oak behind it, and then through 6 feet of dirt behind the oak....

the truly awesome (ridiculous?) wounds are cause by speed.   Shoot the same whitetail with a very light for caliber, rapid expanding, explosive bullet driven to 3200 fps and kaboommm, its shredded meat.  think along the lines of something like a 140 ballistic tip at firewalled speeds out of a 28 Nosler, or a  Hornady VMAX at max velocitites out of a 300 Weatherby. It'll get ugly....

Of the dozens and dozens of deer I've killed, one of the farthest running deer with the  least impressive wounds was nailed exactly right with a 350 Rem Mag shooting 225 grain nosler Partitions at just under 2700 fps.  Again, tons of deep penetration coupled with limited expansion.  Wounds are surprisingly narrow.

A buddy also used 375 H&H extensively on deer.  In most cases, its a deep penetrating bullet at speeds of what, 2700-2800 fps?  In other words, a vary large scaled up 30-06 with a 180 grainer.  The typical 150 remington corelokt or win powerpoint makes a bigger mess.

The killing power of big cartridges at modest speeds (2600-2800 fps) is based on del penetration.  they kill BIG critter reliably, but don't make huge messy gaping wounds (that would run contrary to the design intent of the cartridge).  The huge gaping wounds (which, when you think of it, are really stupid) are caused by lightly built bullets at reply high speeds.... instead of expanding, they explode.

Using a light for caliber bullet, designed for slow impact speeds and then driving them 300, 400 or more feet per second faster, pushes bullets beyond their design limits.  An extreme example would be using 45 colt hollow points in something like a 45-70 or 458.  Or using 158 JSP for 357 pistols in 35 Rem.  You are now into explosive bullet territory.  Expect a very wide but very shallow wound, complete shoulder loss, and a real waste.  

Your 300 HP in the 458 will be similar.  This sounds counter intuitive, but you'll act sully get BETTER performance if you load that bullet to slower than 458 speeds.  If its designed for 45-70 speeds, and its driven too hard, it will not do well.  If you cut back the muzzle velocities so you are shooting at high end 45-70 speeds (sort of a 458 lite), you'll do fine.

No it isn't.  The original question was "how big an exit hole do you think it will make?"

A .45 caliber sabot will probably make an exit hole similar to a .45 cal bullet.  Elephant guns aren't the magical world stomping contraptions some folks think they are.

If using a bullet designed for 458 WM or Lott then you will see little to no expansion.  Like has been said by many others about using a 45/70 bullet designed to expand at low velocities you will see bullet failure and plenty of meat damage.  Still not going to look like a prairie dog after it's been hit by a high velocity varmint bullet.

You might be wise to go to the bigbore section of accuratereloading dot com.  Velocity makes a difference on the size of an exit hole, if there is an exit hole.  There is nothing magical about how big bores perform, but they do follow the laws of physics just like anything else.  The bullet has to withstand the impact to do any good, and a 300gr Hornady will not in a 458 win, which is what he had in mind.  It'll fragment, so you may get some small holes out the back side on deer.  It was designed for 45-70 velocities.  Big bores, in particular, have target velocities that bullets are designed for.  400gr 416 caliber are designed to work around a 2400fps muzzle velocity.  300gr 375 caliber are designed around 2500fps muzzle velocity.  458 caliber drifts into several different camps.  You have 45-70  speeds, and bullets designed to work with those speeds.  You have 458win mag speeds, which is around 2000-2100fps on a 500gr bullet, and then you have the big 458 mags, which push 2300-2400fps with a 500gr.  Lighter bullets for those magnums are designed to work with higher speeds obviously.  You take a magnum bullet design and run it at low velocity from the muzzle, it'll have reduced expansion if it expands at all.  Take a 45-70 bullet and push it at magnum velocities, it'll expand violently, and in many cases it will outright fail.  There is a complete terminal performance sticky on there, if you care to learn.

I can say with 100% certainty that a neck shot will indeed exit and while doing so will take a good portion of spine and meat with it. A large can of Campbells chunky soup would have fit in the exit.  Most likely due to bone blast and not bullet.  A chest shot on a large doe vaporized her heart and lungs and left a quarter size exit.  I am no doubt driving that bullet too fast for its design..

.458, I don't know.  But my .454 does less damage than a 12 gauge sabot and a little more than a .54 patched round ball.