That's interesting...because 2 of the 3 patches at 40grns are exactly what they should look like.
Anyway, your tests prove to me that the fire is NOT causing the problem...it's either tearing during short start or there is/are sharp lands in the bore.
The next most logical thing to me is they're tearing at short start as someone else mentioned earlier...easiest thing to me would be to get a brand new 'FRESH' bag of patches, from a completely different place from where you bought the first ones, in case the ones you've been using are somehow rotted from age or improper storage, etc, and are pulling apart under the strain of being short started.
Assuming the replacement bag of patches is good fresh stock, and they still shred at 40grns, it's gotta be something in the bore.
By the way, when you get new fresh patches, if you have a ball puller or an air compressor, one quick check of the bore would be to seat a patched ball WITHOUT any powder, then using a ball puller or compressed air, pull it back out and see if the new patches are cut.