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Jayhawker
ModeratorManistee Natl ForestPosts: 18,291 Senior Member
.308 Winchester supersonic at 1100 yards?
Jayhawker
ModeratorManistee Natl ForestPosts: 18,291 Senior Member
Saw an ad in the American Rifleman comparing the .308 to the .338 Lapua. Claims the .308 is supersonic to 1100 yards while the Lapua is supersonic to 1800 yards. This does not hold true in my experience...some of it from shooting the .308 at 1000 yards and some of it from working in the target butts....(you can hear a supersonic round going over your head) Hell, I've seen .308s that didn't make it to the 1000 yard berm.... What's your take on this claim?
Sharps Model 1874 - "The rifle that made the west safe for Winchester"
Replies
The big problem for years was that folks forgot that the 168 grain Match King was originally designed as a 300M International fullbore slug, and forgetting this, complained bitterly that it wasn't cutting it at 1000 yards.
The 175 grain Match King was introduced to solve this - IIRC, out of a 20" M14 no less. Longer barrels with faster twists at the right altitude. . .sure.
Then there's the 155 grain Palma bullet - undersize bores and long barrels, yes, but reliably rocking at 1000Y for decades.
There was a sniper kill in Vietnam with a .308 from a firebase tower in excess of 1200 yards. This would have been the 173 grain FMJBT. Supersonic at that range? Stable through the trans-sonic? Just extremely lucky?
All that is AT LEAST 10-15 year old tech.
"Nothing is safe from stupid." - Zee
As with most things in life, it depends.
If you ask a Fullbore or Palma or Highpower or F-class shooter about getting to 1000 yards supersonically with a .308 Winchester, you would get many valid answers. It's not difficult and 100 yards more is no big deal. But there are caveats.
It's really going to be about bullet choice and barrel length. In regular barrels, and at sea level in summer time, most any .308 ammo will be supersonic to about 8-900 yards. I've seen people come to the line with their 20 and 24 inch barrel and shoot Berger 185s or 155SMK and get to 1000 yards barely supersonic; not sure if the added 100 yards would still see the bullet above Mach 1.
But when you shoot a higher BC bullet and you push it out of a 28 inch or longer barrel, getting to 1000 or 1100 above Mach 1 becomes very feasible.
For example, my F-TR match load consists of a 180gr boutique bullet pushed out of my 32 inch barrel at over 2800FPS. At sea level, where I do most of my shooting, that bullet is above Mach 1.4 at 1000 yards and according to JBM goes transonic right after 1500 yards; the product of high BC and high MV.
When I first started in competition in 1982, we shot Fullbore with issued ammo. The barrels where long, 30 inches, but the ammo was crap. The bullets were 147gr FMJBT, the NATO stuff. At 1000 yards, none of the bullets were supersonic and many were coming in sideways or at least creating oblong holes.
It was epic.
"The Un-Tactical"
Berger makes a 210 gr very low drag bullet ( .63 bc ) in .308 that is barely supersonic at 1100 yards if shot at 2200 FPS, so it is doable.
Is there any military ammo?
D
Alcohol, Tobacco, Firearms and Explosives.... now who's bringing the hot wings? :jester:
Now, let's be clear about a few things here. When the bullet goes transonic, it doesn't mean it falls out of the sky right at that moment, it continues on trajectory. How close to intended trajectory is what is variable. Most bullets, especially the ones designed for long range seem to remain point on after going subsonic. There are a few well-known bullets that will become unstable going transonic and will be tumbling once they go subsonic. The 168SMK is the poster child for that and while it's a great bullet for short range (300-600 yards), the angle of its boat tail is such that its BC is affected and it slows down faster than it should and its weight distribution will cause it to become unstable during the transonic passage.
Other bullets like the 175SMK or the much better Bergers and JLKs and so on, will not usually tumble; they will remain point on to the bitter end.
One must understand that a bullet actually becomes more stable as its forward velocity diminishes, since its rotational velocity remains fairly constant. The overturning forces are diminishing, but the gyroscopic effect that kept the bullet stable from the muzzle is still going strong. Except of course for the 168SMK.
I believe the .mil has something called M-118 LR that is a .308 Winchester (7.62X51) loaded with a 175gr SMK. That's probably the best .308 loading the .mil has and it's rather pitiful compared to handloaded match ammo. The FGMM factory ammo is the same thing. If they ever started to use better bullets, that could get interesting but that will never happen.
"The Un-Tactical"
I'm not questioning whether or not the .308 can be used to engage targets at 1K+...we know it has...Jim Gilliland pulled off a 1250 meter kill shot in Iraq in 2005 using a 7.62 X51 ...the question is whether or not the bullet is supersonic when it gets there....it appears the answer is..."it depends"...