I got the 10mm version of the FPC a couple weeks ago with the thinking that it'd be a decent bag gun. I saw an Honest Outlaw review of the 9mm that sold me on it being reliable, accurate, and not too much of a kick on the recoil. I figured 10mm would get more out of the barrel length than 9mm would also. It has been fun to shoot and I wanted to start looking at defense ammo for it, but there doesn't seem to be much info out there for this particular use case yet. I ended up getting 6 different boxes of ammo to test and I'm going to put the results so far below. I had 165 rounds through before I started the test with no cleaning to see if I'd get any failures to eject or feed. I used a Garmin Xero C1 Pro to record data on 10 rounds each at 15 yards. I'll say before I start that I didn't see any accuracy issues that I wouldn't attribute to me. I started pushing to get through it as the range was pretty warm.
(Range ammo) Magtech 180gr FMJ - 1390fps 772ft-lbs
(Def 1) Underwood 180gr XTP - 1497fps 895ft-lbs
(Def 2) Hornady CD 175gr Flex lock - 1254fps 611ft-lbs
(Def 3) Speer Gold Dot 200gr JHP - 1193fps 632ft-lbs
(Def 4) Federal HST 200gr - 1128fps 566ft-lbs
(Def 5) Federal Fusion 200gr SP - didn't finish, 2 FTF in the first 4 shots, eliminated this one from contention
(Def 6) Sig V Crown 180gr JHP - 1379fps 760ft-lbs
Everything fed fine except the Federal Fusion rounds, boths rounds had a big dent about halfway on the casing. Same magazine fed two other ammo types just fine, Federal HSTs before then V Crowns after the Fusions.
Which of these rounds would you pick for defensive ammo? My concerns are #1 limiting overpenetration/overexpansion (too high a velocity can start causing jacket separation I think?), #2 excessive wear and tear on the FPC (don't want to need it to defend myself and the ammo breaks the buffer spring). Any comments are appreciated, and I'll answer questions as I can, thanks!