I've not had a problem with TSX's feeding in my M70, however I handload. With respect to you saying they were seated to spec, what did you measure them to? SAAMI is 3.6", but my Barnes manual says to seat them to 3.57" with a minimum 3.54" length. Can you see that it is actually hanging up on the front of the bullet? I say this because I went through an issue with my M70 in that it doesn't like to feed non-crimped rounds. After fiddle farting with it, I watched very closely as I chambered a round and could see it actually hanging up on the "face" of the brass at the neck. Most factory rounds are crimped so this shouldn't be an issue, but can you see on yours if they're crimped into one of the grooves?