3 weeks, 6 days ago
We have previously discussed the Marine Corps battle with the Army and Congress over fielding a different ammunition than the Army, who spent a wad of money on an “environmentally friendly” lead-free cartridge, the M855A1.
Currently, the Marine Corps is trending towards the MK 318, which appears to be a far superior round, and it comes in right at 2900 FPS out of the M4 barrel, higher for longer barrels. The claim is that it behaves better at longer distances and retains its ability to penetrate.
This trend towards heavier rounds has been going on for some time now, and 62 grains isn’t the top weight for the 5.56mm bullet. One reader sends information about Sierra 77 grain, and tells me that the 1:9 twist is just fine with this ammunition. Of course, one gives up something to get something. In the case of heavier bullets, you give up muzzle velocity.
This velocity detriment may seem small. TFB likes the Sierra 77 grain, and informs us that its muzzle velocity comes in somewhere between 2500 FPS and 2600 FPS. But your choice of ammunition will depend upon your target, its distance, any interstitial shielding, potential body armor, etc.
You may do better with M193 than with either the MK 318 or the Sierra 77 grain. Sometimes the smaller rounds with the higher muzzle velocity are what’s needed to penetrate any armor. Do you not believe me? Consider what we learned with the FN 5.7 and its test against bulletproof glass, which only the .454 Casull could penetrate. The open tip 5.7 round at 22 grains penetrated the glass due to high muzzle velocity, whereas the heavier 5.7 round did not.
Do you need more evidence? Very well. Consider that AR500.com sells hard plates it calls Level III, and those plates are rated to stop M855 (steel core) but cannot stop M193. They have to move up to what they call Level III+ to perform effectively against the M193 due to its higher muzzle velocity compared to the M855. There’s nothing wrong with having a safe full of M193.