Porcupine wrote: ↑
Mon Aug 03, 2020 7:14 pm
yovinny wrote: ↑
Mon Aug 03, 2020 5:58 pm
Porcupine wrote: ↑
Mon Aug 03, 2020 3:21 pm
It was all about penetrating body armor, and helmets that we expected to encounter in a major conflict. The reduced soft tissue damage was considered an acceptable trade off.
Dependent on atmospheric conditions, the slow twist with the longer (heavier) projectile would result in failure to stabilize at all.
Twist rate does not affect terminal ballistics, but the orientation of the projectile on impact will.
No “guise” on the 1:7. Tracer rounds are very long, they need to spin faster to stabilize.
It wasent about body armor at all,, there was little in use then in 1980..look it up.
It was about helmet penetration,, and the test standard was the German helmet...look it up.
Projectile rotation absolutely has to do with terminal balistics,, as testing has indicated, over and over, since the first Sweden tests...look it up.
The FNC with 1:12" twist barrel passed all of Swedens penetration and accuracy testing,, it was changed to 1:9 because of instability with soft targets...Look it up..
1:9 will stabalize M856 within accuracy standards,, which if your not aware, is actually much larger and about 2.5x the M855 standard.
Tracer never has been and isent intended to match ball ammo accuracy standard,, its for use as general area spotting.
I was there- I don’t have to “look it up”.
I mentioned helmets, and body armor was STARTING to become a thing in first rate militaries. Not yet fielded in quantity, but we thought it was coming. The requirement was to “PENETRATE” the helmet/armor- by definition having to do with penetration
Tracers are significantly longer than ball rounds so they require a tighter twist to stabilize well.
Since the weight of a tracer changes over its flight, it’s not expected they’ll be particularly accurate.
The purpose of the progressively tighter twists is to stabilize the longer and longer projectile. The purpose of going to M855 was to improve penetration against lightly armored targets. The move to the longer projectile necessitated a tighter twist. The twist has nothing to do with wound profile.
Well,, if 'you were there',, you would know that the US trial rifle was the m16a1 with 1:12 twist barrel and xm777 ammo (which was the US's experimental version of ss109 and was what would become m855)
It failed testing because of the ammo itself, not the twist rate, as later testing found the penetrator cores at fault.
Our early experimental manufacturing techniques of said ammo failed to produce rounds with the penetrator core centered and concentric within the bullet. This condition caused havoc with accuracy and resulting penetration,, not the twist rate.
The fact FN developed ss109 specifically for the FNC 1:12" twist and Swedens FNC testing shooting ss109 passed all accuracy and penetration tests, should convey something to those without a mental block and inability to accept factual test results contrary to their incorrect predetermined notions.
Some also seem to believe that ss109 at 1:12" twist, that has a tendency to upset and tumble on soft tissue contact and m855 at 1:7, that has a tendency to not upset at all and drill tiny strait through holes, have nothing to do with physics or the barrel twist....
I have no issue shooting good m855 in my handfull of 5.56 rifles with 1:12" twist without accuracy issues that would prevent it being combat effective...Just like I had no issue shooting m856 in 1:9 twist.
Anyone with an open mind should test it out yourself,, before excepting internet falsehoods as gospel truth.