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Posted: 1/2/2006 10:52:44 AM EDT
If , according to the ammo oracle, common belief on this site, and use by the military special forces, 77 grain out of a 1/7 twist 14.5 inch barrel is superior to 62 grain out of the same barrel, how is that 55 grain is somehow superior to 62 grain as well? The ammor oracle itself sttes 55 grain i.e. XM-193 is superior to M855 ball.

Wouldnt it stand to reason if the 77 grain is superior to 62 grain wouldnt the 62 grain then be superior to the 55 grain?
Link Posted: 1/2/2006 10:56:16 AM EDT
It's all about fragmentation. The 55gr fragments more reliably than the steel tipped 62gr. 77gr fragments reliably at a lower velocity than either of them. Lower frag velocity=longer frag range.
Link Posted: 1/2/2006 11:35:22 AM EDT
[Last Edit: 1/2/2006 11:37:45 AM EDT by O-320]

Originally Posted By topgunpilot20:
It's all about fragmentation. The 55gr fragments more reliably than the steel tipped 62gr. 77gr fragments reliably at a lower velocity than either of them. Lower frag velocity=longer frag range.



+1

ETA: You might get more responses if you asked in the AR15 Ammunition forum.
Link Posted: 1/2/2006 12:14:01 PM EDT
Not only is fragmentation a concern, so is accuracy.

M855 is less accurare than M193 due to the fact that the steel penetrator slug inside the M855 bullets is rarely concentric with the rest of the lead core.

That lack of concentricity will make the bullet wobble as it spins on its way to the target, creating far more shot to shot dispersion in point of impact than M193, which uses a one-piece lead slug as its core.
Link Posted: 1/2/2006 12:46:39 PM EDT
As a general rule, the closer you are planning to engage targets, the lighter the bullet.
Another consideration is the barrel length.

If you are going to engage targets close up, the 55 grain will fragment reliably. The 62 grain (M855) is not going fast enough out of the short barrel to fragment reliably. The 77 grain fragments at a much broader velocity range, so it is better suited out of short barrels or long range engagements.

I think of it as with standard barrels, 16 or 20", 55 grain is best for ranges out to 150 yards. If you are going to engage targets beyond that, M855 is superior. If you are going to engage targets at extreme ranges, 300 yards plus, then the 77 grain would be best.

Out of the short carbines, 77 grain is best at almost all ranges.
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