That sounds like every bulged barreled S/W 45 auto Ive had. Without reading all the previous entries. I remover grips ,sideplate, sear, fish out the safety levers, disconnect etc.Same with decocker assy and firing pin/spring. This is mostly just to inspect them.See if they are broken,chipped . Never been the case, that Ive seen.
Then usually end up driving out the slidestop ( on the 45s it shears off the inner lip of the slidestop but its pretty thin on the 45) dont know on the 40 cal. And lock frame in padded vise and tap slide off forward.
Ive done at least a dozen 45s, all after we added 40 cal to our ammo ,and guys would somehow get a 40 cal round in with the 45s. The 40 would fire , next round pushing the 40 case into the barrel and there you go. Same could happen with 9mm in a 40 cal mixup. Every one only needed a new barrel and slidestop and they were good to go . Just my experience, good luck. Bob