Ok this scares me and I am fearless. About ready to sell my 550. Very seldom do my bullets match what the manuals use and some of the COLs don't feed in my M&Ps. I would think you could look up the bullet they used and get the length compare it to the length of your bullet then the length of the case they used. You should be able to figure their seating depth then figure what your bullet needs to be seated to and then if your gun will eat it it is probably ok, MAYBE. Am I wrong. I can't tell how far my brass flys as it bounces off the partition ever which way. I guess I never seen a flat primer and not sure what it looks like if I had one. When loading 12ga in the 60s a over load would make the case head concave. Seen that we would 10ga loads in 12ga mag cases by reducing the wad column. I was young and dumb then.

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USN Retired/VN VET
M&P X5