Lee White wrote:
"I think it HIGHLY unlikely that a true Whitworth would have burst." Jo Whitworth worked hard to build that reputation of strength for his artillery, but they were in fact rather fragile. His "fluid-compressed steel" for example, was a post-Am.Civ.War development, and whether that strengthened his guns is still debated. His guns did indeed "burst," or were so described:

During Gen. Longstreet's Tidewater campaign from mid-March to April, 1863, several Whitworths (certainly breech-loaders) were used, and were effective: "The Whitworth solid shot pierced through the iron plates about the boat [the U.S.S. Commodore Hull] and pilot houses as if they had been of paper" reported Act'g Master W.G. Saltonstall (O.R.Navy v.8, p. 692). The Confederate battery (Lane's)which did this damage had "burst four of his guns at Rodman's Point, two [one] Whitworth and two Parrott rifled" (O.R.Navy v.8, p.684). Confederate Major James Dearing acknowledged this: "[Capt. John] Lane's Whitworth gun burst in North Carolina" (O.R. v.18, p. 335). Note, both sides used the word 'burst.' By April 25, though, R.E. Lee reported: "The Whitworth gun of Lane's battery is, I understand, in Richmond, repaired. I fear it was disabled by carelessness in loading" (O.R. v.25-2, p.749). One might infer the gun had "burst" it's breech-cap.

Re: Raymond, Br.Gen. John Gregg reported only: "Captain Bledsoe, with his artillery (one of the pieces of which burst during the engagement), continued during the whole day to keep back the enemy." Nowhere does Gregg (or anyone else) say that the burst gun was even a rifle, let alone a Whitworth. No one (that I've found) identifies any of Bledsoe's three "pieces" used that May 12.

A week later, in Vicksburg: "One Whitworth gun on my [F. A. Shoup's] line was disabled on May 19, from effect of its own shot." This must be the same as the "one Whitworth gun, which also burst the first day" according to W. A. Baldwin (reitterated in table, p. 405, O.R. 24-2). Someone's second "Whitworth gun, waspish in its annoyance" was in operation on 22 May (v.24-2, p. 269), unless misidentified by those under its fire.