I don't know about lengthwise through a horse, (I doubt that), but a 120lb deer, certainly.
In fact, when my friend shot the deer and armadillo's, we in fact were pig hunting. Most of our "pigs" run 75-300lbs, or within the extream range of size (roughly) of our deer.
Pigs are certainly in peril from a .45lc with lead bullets.
My LRFN's are the Lee mould. They've got a much larger meplat than the original flat point round nose factory swaged bullets.
A "carbine" or rifle load with the loading we are using is ~1,200fps. Not enough to expand greatly, but enough shock to be ultra effective. Can't say just how much expansion as I/we haven't recovered one shot into game.....
Consider that the .45colt was orginally a duplication of the dragoon revolvers which indeed were "horse pistols".
If they will take down a 1,000lb horse, they'll do on 300lb pigs....
The military didn't even for long issue such powerful handgun loads. The original 40gr BlackPowder load was soon loaded down to ~28gr, which in effect duplicates the .45acp loads.....From a handgun.
The only real reason to increase the m/v of these loads is to flatten trajectory. At 1,200fps. the trajectory is essentially that of the .22lr. A 4" high zero at 50yds yeilds a zero at ~100yds... and 4" low at 125yrs... About as far a you can see to shoot where we use such "hardware".... So not a "handicap".
The deer he has shot have been diagonal chest shots, and have penetrated 18-25" of deer before exiting with 1-2" exit wounds. Short double blood trail...