How is it that the Church can accept private revelations which say that Jesus received 5,115 blows during the Scourging, when Roman Law limited the scourges to 40 or even 39? The Mystical City of God says this is the number of blows He received during the Scourging.

Even if you were to count each individual stripe that the Roman flagrum had as separate blows, for instance, if it normally had 3 stripes with a little metal dumbbell attached, even this would be 3x40=120 scourges. Even if you wanted to make it 5 or 6 stripes per flagrum, it would still be 300 and 360 respectively, nowhere near 5,115.

And if you were to suppose Roman Law was set aside in the case of Our Lord, would not that have been mentioned in the Gospels to show how much more brutally they treated Him?

Those of Anne Catherine Emmerich, which i deem unreliable because they were tampered with by Clemens Brentano, say that the Scourging took 45 minutes, which would also make the total number of scourges in the thousands, not 40.

As a side note, does anyone else believe that the Scourging as portrayed in Mel Gibson's movie is inaccurate? I mean the multi-headed claw-shaped flagrum. I have seen pictures of actual flagrums and they were dumbbell-shaped like i mentioned, not claw-shaped. This is also what is seen in the Shroud of Turin, dumbbell-shaped marks. I believe these claw-shaped ones would have attached themselves to bones all over and would have broken them, they're too deadly.

I would say that it was out of sheer animal rage that Roman Law went out the window in the case of Our Lord.

In his writing about "the many" (ie many are called but few are chosen), Fr. Wathen writes.........

Among the realizations which the Lord Jesus wept and bled for
in the Garden of Gethsemani is this: No matter what He might do to
save them, the "many" will hate Him for it; they will take all His
material, earthly gifts, and devour them like pigs, and ever clamor for
more. But of gratitude and repentance, of faith and love, they will
have nothing. These accursed souls are personified in Judas, who had
received nothing but kindness and honor and enlightenment from
Christ. Let The Deniers give an explanation why Judas did not just
walk away from Christ, or tell Him that he had lost interest, that he
liked the feel of money, and had decided to open a clothing store. No,
he must sell his Master, Him Whom, for months he had seen as the
sweetest, most thoughtful, most patient, and wisest of all the men of
his experience.

The "many" are personified in Pilate, whom Our Lord tried
sincerely to save, while He proceeded to thwart Pilate' s lame efforts
to save Him. But Pilate, like ninety-nine percent (or thereabouts) of
those in public office, determinedly thrust away the grace. It would
have been perfectly easy for him to save Jesus and his own soul (The
Savior of the world stood right before him, subject to him!-as He
does to every man, in the Church), but he chose to do everything the
wrong (and harder) way.

The "many" are personified in the scribes and Pharisees, the
priests, and Annas and Caiphas, who knew perfectly well, as
Nicodemas said, that Christ had come "a teacher from God," (Jn. 3:2).
They knew that His miracles were authentic, that His character was
blameless, that His teaching was irresistible and holy, that He was a
luminous exemplar of every man of religion. "He saved others; himself
he cannot save" (Mt. 27:42 and Mk. 15:31)., they said, thus admitting
the former truth, while closing their eyes to any explanation
for the latter.

The truth was clearly before them, as the truth of the
Catholic Church is before the men of the world of this and every other
generation, but they were determined to reject Christ, and in order to
justify their doing so, they must convince themselves and everyone
around them, that He was not what He appeared to be. Furthermore,
they will not be content simply to let Jesus go. They must kill Him;
and not kill Him merely, but kill Him cruelly and ignominiously.
They must somehow vent their resentment of His grace and His
majesty and His holiness against Him, to teach Him that they would
bow to NO ONE, save each other. They will take their revenge
against Him, Whose very divinity they could not deny, Whose resurrection
they could not disprove. Mutatis mutandis, the very same can
be said of all those who have rejected the Church, from that day to
this one. If they would only make an effort, it would be no problem to
them, but they will not. And the Lord Jesus, there in the Garden, saw
that they would not, and it sorely grieved His Sacred Heart to foresee
it.

From The Pieta Prayer Book

Be it known that the number of armed soldiers were 150; those who trailed me while I was bound were 23.  The number of executioners of justice were 83; the blows received on my head were 150; those on my stomach, 108; kicks on my shoulders, 80.  I was led, bound with cords by the hair, 24 times; spits in the face were 180; I was beaten on the body 6666 times; beaten on the head, 110 times.  I was roughly pushed, and at 12 o'clock was lifted up by the hair; pricked with thorns and pulled by the beard 23 times; received 20 wounds on the head; thorns of marine junks, 72; pricks of thorns in the head, 110; mortal thorns in the forhead, 3.  I was afterwards flogged and dressed as a mocked king; wounds in the body, 1000.  The soldiers who led me to the Calvary were 608; those who watched me were 3, and those who mocked me were 1008; the drops of blood which I lost were 28,430.

Those of Anne Catherine Emmerich, which i deem unreliable because they were tampered with by Clemens Brentano, say that the Scourging took 45 minutes, which would also make the total number of scourges in the thousands, not 40.

Duration is irrelevant; it's possible that, due to being under orders not to kill Our Lord, they took some breaks; otherwise the trauma and pain would have been enough to send someone into shock and kill Him.  There's some Arab guy being punished with caning right now, and he gets a couple weeks' break in between sessions.