Any Lake City ammo is good for training, but out of a 10.3" barrel don't use it for defense. The 5.56 fmj's depend on velcoity to "break" the bullets and cause cavitation and fragmentation. If they don't they make a narrow wound channel and over penetrate. With the 10.3" and M855 I got around 2600 fps, and the absolute frag velocity is around 2500 fps which means your below 2500 fps under 50 yards. Even then the wound channel neck (area after penetration and before cavitation) will be long, up to four or five inches. For the 5.56 in general, and 10.3 especially, look at soft points. Federal 62gr tactical, Speer 64 grain Gold Dot, Federal 64 grain Tru, etc. Even 55 grain soft points are nasty little buggers. We use the Federal tactical at my agency and it has worked well. It is a bonded bullet and expensive. I've been testing the Federal Tru 64 grain soft points and have been very impressed. Soft points require a much lower velocity to expand and fragement, (1800 fps) and are great HD performers.
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