Some comments
Lead is heavier than steel That's why the M855 bullet which is much longer but only weighs 7 grains more than the 55grain M193
The green-tip SS109 aka M855 aka 556 degem-bet bullet needs more spin because it is longer, not because it is heavier, than the old M193
1:7rifling was needed due to the orange-tip M856 tracer bullet which is ever longer, For the M855 1:9 is enough.
Both 556 bullets are covered with a copper jacket which is what interacts with the rifle grooves. Not the lead. Part of the reason that lead bullets began to be covered in copper jackets over 100years ago is to prevent the rifle barrel grooves from getting quickly fouled with the soft lead from the fired bullets
The M855 cartridge explosion and recoil is NOT stronger, nor uses more powder than the M193
The barrel does not need to be thicker or stronger to handle the M855. This was done for other--and apparently mistaken---reasons. Fact is the barrel of the A3 is only thicker at the muzzle end. The other two-thirds under the handguard is just as thin as on the A1.
If you don't believe me, just take a look
M193 is faster 3250fps vs 3100fps for M855 --- muzzel velocity from 20inch barrels
Firing M193 from 1:7 barrels is NOT innaccurate-- see below
M855 is preferable for its accuracy and its flatter trajectory vs M193 only beyond 300/400m--it was originally designed by FN for the Minimi LMG after all
However I can think of 3 advantages for using the M193 bullet, even in 1:7 barrels
-It is cheaper
-tends to be more accurate due to a simpler production procecess
-tends to fragment more often than the slower M855
Much more information here:
ציטוט:
I shot both dor-alef M193 (marked A1) and dor-bet green-tip M855 (marked A2) ammumition at this target from a long barreled M16A1 with 1:12 inch rifling twist.
It's clear how the under-stabilized M855 (marked A2) bullets enter the target almost sidways at a range of only 10 meters.
BTW I want to dispel a common myth that I hear in the IDF: that firing M855 from the 1:12 barrels will damage the weapon or is dangerous-- The US ARMY manuals say that If you run out of ammo its ok to use the M855 in with 1:12 barrels--you just won't hit a target unless it's very close
The other way around is fine. Despite what the shooting-instructor soldierette told me, after running out of M855, I was able to hit a target at 300m at night using regular M193 ammo from the A3.
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צ'אט
24-09-2007, 19:45
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