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Old 04-02-2011, 10:57   #1
Buffalobob
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New Transonically Stable 308 Bullet

Berger has designed and tested a new 308 bullet that will pass through the transonic zone without being upset. It is not yet listed on their website but is in the production line. Bryan Litz, the ballistician for Berger has loaded ammo listed for sale on his website. It may have some interesting applications for the military in terms of extending the range of the 308 sniper rifles.

Here is the link

http://www.appliedballisticsllc.com/TacticalAmmo.html
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Old 04-02-2011, 13:10   #2
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Interesting. Nowhere in that page do they indicate what their muzzle velocity is out of the 20-inch OBR.
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Old 04-02-2011, 21:14   #3
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You should duly note that it is not ammo loaded by Berger. It is loaded by Bryan who keeps his personal company even while an employee of Berger.

I would suspect it is not loaded to any extreme velocity for insurance liability reasons. I would imagine out of a 20 inch barrel you could get 2500 to 2550 fps depending on lots of factors.
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Old 04-02-2011, 21:27   #4
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Does barrel length and rifling have much affect on transonically stabilizing a bullet? I have a friend who builds custom tactical rifles and he made one with a barrel that was about three feet long. He was trying to explain it all to me but I was in a hurry that day and I didn't quite get all of it. Just curious.
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Old 04-03-2011, 00:12   #5
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Quote:
Originally Posted by Brush Okie View Post
Some tests done a few years ago found that there is very little to no velocity loss out of a 20 in barrel for a .308 depending on the powder. Here is a link to an article I found using my google-fu

http://www.tacticaloperations.com/SWATbarrel/

And and except from the article.
That would equate to about 4FPS for each inch of barrel length lost.

Last edited by mojaveman; 04-03-2011 at 00:15.
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Old 04-03-2011, 05:45   #6
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Does barrel length and rifling have much affect on transonically stabilizing a bullet? I have a friend who builds custom tactical rifles and he made one with a barrel that was about three feet long. He was trying to explain it all to me but I was in a hurry that day and I didn't quite get all of it. Just curious.
Most serious 1K competitors using the 308 will use a 28-30 inch barrel. They will hand load their own ammunition and will push pressures as high as they can without affecting group size. The idea is to achieve high velocity to minimize wind drift and drop variations and to stay above Mach 1.2.

Barrel twist is not especially important to transonic stability above and beyond regular stability concerns. Bullet shape is important. Shallow boat tail angle and no meplat or very small meplat, and short bearing surface seem to be important. Interestingly, the old black powder buffalo sharps aficionados shoot cast lead bullets very accurately far beyond the transonic zone.

As far as the Swat study I have not shot any factory loaded rifle ammo in three decades so I just don't have any knowledge base concerning burning rates of the powder used.
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Old 04-03-2011, 15:02   #7
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The 308 is no longer used by serious 1000 yard shooters these days.
I assume from your statement that you have never actually done any competition shooting at long range. There is a whole group of F-class called F-T/R which includes only 308 and 223 (military calibers ). It is what I shoot and what I trained my children to shoot. I have posted several videos of my children shooting in long range F-class with a Rem 40X in 308. The 6.5-284 competes in a class called "open" which is not head to head with the 308.

Do you actually know anything about bullets and the transonic zone and killing people?
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Old 04-03-2011, 18:23   #8
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Quote:
Originally Posted by Buffalobob View Post
Bullet shape is important. Shallow boat tail angle and no meplat or very small meplat, and short bearing surface seem to be important.
Ahhhh…
I can see the meplat being an issue, as a hollow point degrades the BC of any rifle bullet, but I had not considered the boat tail. If the instability derives from changes in the bullet’s shockwave as it crosses the transonic plane, which was my uneducated guess (and which turns out to be not quite accurate), my attention would be on the front of the bullet. Being a short-range shooter (nothing much past 200) and fond of flat base bullets, I would not have considered the effect of the vortex following the bullet. The short bearing surface will help at both ends of the bullet, or put differently, will result from reducing bluntness up front and lengthening the taper of the boat tail.
Will an epoxy filled nose and a rearward center of gravity help things here?
And where is Longrange1947? I’d like to hear his input on this.

A little Google-fu helped throw some light on the issue for me: rather than looking at the bullet, it got me looking at aerodynamics, specifically, the transonic zone:

Quote:
http://answers.yahoo.com/question/in...3211733AA9JEeY
The Transonic zone is a condition of speed when some parts of the air flowing over an object, such as an airfoil are supersonic already and some parts are not. The term to watch between the transonic zone and the supersonic zone is called the Critical Mach number...where the airlow in some parts of an object, again, the typical example would be an airfoil..reaches the speed of sound, even though other parts of the aircraft has not crashed through the sound barrier. When this condition is reached, it will create a weak shock wave.

A shock wave is a condition where a there is always a rapid rise in pressure, density and temperature. As the aircraft approaches the transonic zone--Mach .80 to Mach 1.2--the pressure waves do not have time to move out of the way of the oncoming aircraft since it is traveling along with them. The waves compress and the air becomes far more dense. When the plane meets the compacted air, it hits with a jolt and a series of shock waves builds up perpendicular to the direction of flight. The first shock wave attaches itself to the center of the wing's upper surface as the airflow there reaches Mach 1, As the plane's speed increases, the air under the wing also reaches mach 1 and a second shock wave forms....
Quote:
http://www.centennialofflight.gov/es..._Flow/TH19.htm
An airplane flying well below the speed of sound creates a disturbance in the air and sends out pressure pulses in all directions. Air ahead of the airplane receives these "messages" before the airplane arrives and the flow separates around the airplane. But as the plane approaches the speed of sound, the pressure pulses merge closer and closer together in front of the airplane and little time elapses between the time the air gets a warning of the plane's approach and the plane's actual arrival time. At the speed of sound, the pressure pulses move at the same speed as the plane. They merge ahead of the airplane into a "shock wave" that is an almost instantaneous line of change in pressure, temperature, and density. The air has no warning of the approach of the airplane and abruptly passes through the shock system. There is a tendency for the air to break away from the airplane and not flow smoothly about it; as a result, there is a change in the aerodynamic forces from those experienced at low incompressible flow speeds….
At subsonic speeds, drag was composed of three main components—skin-friction drag, pressure drag, and induced drag (or drag due to lift). At transonic and supersonic speeds, there is a substantial increase in the total drag of the airplane due to fundamental changes in the pressure distribution.
This drag increase encountered at these high speeds is called wave drag. The drag of the airplane wing, or for that matter, any part of the airplane rises sharply, and large increases in thrust are necessary to obtain further increases in speed. This wave drag is due to the unstable formation of shock waves that transforms a considerable part of the available propulsive energy into heat, and to the induced separation of the flow from the airplane surfaces. Throughout the transonic range, the drag coefficient of the airplane is greater than in the supersonic range because of the erratic shock formation and general flow instabilities. Once a supersonic flow has been established, however, the flow stabilizes and the drag coefficient is reduced…

It is a large loss in propulsive energy due to the formation of shocks that causes wave drag. Up to a free-stream Mach number of about 0.7 to 0.8, compressibility effects have only minor effects on the flow pattern and drag. The flow is subsonic everywhere. As the flow must speed up as it proceeds about the airfoil, the local Mach number at the airfoil surface will be higher than the free-stream Mach number. There eventually occurs a free-stream Mach number called the critical Mach number at which a supersonic point appears somewhere on the airfoil surface, usually near the point of maximum thickness, and indicates that the flow at that point has reached Mach 1. As the free-stream Mach number is increased beyond the critical Mach number and approaches Mach 1, larger and larger regions of supersonic flow appear on the airfoil surface. In order for this supersonic flow to return to subsonic flow, it must pass through a shock (pressure discontinuity). This loss of velocity is accompanied by an increase in temperature, that is, a production of heat. This heat represents an expenditure of propulsive energy that may be presented as wave drag. These shocks appear anywhere on the airplane (wing, fuselage, engine nacelles, etc.) where, due to curvature and thickness, the localized Mach number exceeds 1.0 and the airflow must decelerate below the speed of sound. For transonic flow, the wave drag increase is greater than would be estimated from a loss of energy through the shock. In fact, the shock wave interacts with the boundary layer so that a separation of the boundary layer occurs immediately behind the shock. This condition accounts for a large increase in drag that is known as shock-induced (boundary-layer) separation….

At a free-stream Mach number greater than 1, a bow shock appears around the airfoil nose. Most of the airfoil is in supersonic flow. The flow begins to realign itself parallel to the body surface and stabilize, and the shock-induced separation is reduced.
This condition results in lower drag coefficients. Supersonic flow is better behaved than transonic flow and there are adequate theories that can predict the aerodynamic forces and moments present. Often, in transonic flow, the flow is unsteady, and the shock waves on the body surface may jump back and forth along the surface, thus disrupting and separating the flow over the wing surface. This sends pulsing, unsteady flow back to the tail surfaces of the airplane. The result is that the pilot feels a buffeting and vibration of both wing and tail controls. This condition occurred especially in the first airplane types to probe the sound barrier....
Attached Images
File Type: jpg Shock formation around an airfoil.jpg (63.5 KB, 98 views)
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Last edited by incarcerated; 04-03-2011 at 18:35.
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Old 04-04-2011, 11:35   #9
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This is an interesting subject.

Bryan Litz is engaged in a thread about this subject here:

http://www.usrifleteams.com/lrforum/...ic=13415&st=75

It seems that there are many different issues relating to the stability of a bullet as it passes through the transonic zone and merely by passing through the transonic zone a bullet does not necessarily become either unstable or inaccurate.
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Old 04-04-2011, 16:17   #10
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Originally Posted by Buffalobob View Post
You should duly note that it is not ammo loaded by Berger. It is loaded by Bryan who keeps his personal company even while an employee of Berger.

I would suspect it is not loaded to any extreme velocity for insurance liability reasons. I would imagine out of a 20 inch barrel you could get 2500 to 2550 fps depending on lots of factors.
edit: I'm speaking about 168g

I have a 20 inch barrel on my VTR. My last load I built was hitting 2550, but Hornady Tap comes out 2650 almost every time. I still need to chrono my Federal Gold Medal Match SMKs.

I have the program "shooter" for my android phone. It's my favorite thing about the phone. It seems to me that a lot of though was put into it. It has a lot of G1 and G7 profiles for bullets by Litz. Anyway I can't wait to see this round. I took my furthest shot this weekend at 650 yards. It's the furthest place I've found to shoot.

Sorry for the ramble, I just love shooting at distance.

Last edited by Ramirez; 04-04-2011 at 16:19.
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Old 04-04-2011, 16:20   #11
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Just paraphrasing, but it seems that a shorter, heaver, lead based bullet (no solid copper) that has a high rpm shot from a barrel with shallow, rounded grooves will pass through the transonic zone better than other sorts of bullets. Some posters claim their bullets are accurate 100s of yards beyond the transonic zone, with a couple of Englishman claiming they are shooting targets 2500 yds with .308 subsonic bullets.

Of course, the thread then degenerates into conversations about sabots with fins, true Mil sighting systems, solid copper bullets, etc. In my experience, some of these threads have the same structure as a herd of cats, and not just in that forum.

I’m sure there are people on this board who know about this stuff, but it sure isn’t me.

I suggest you sign on that board if your interested in rifle shooting. It’s free and they have some very interesting threads going.
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Old 04-04-2011, 19:03   #12
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I talked to a USASOC buddy today who has tested some of the AB rounds - he said they shoot very well at 1000m.
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Old 04-05-2011, 08:29   #13
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I talked to a USASOC buddy today who has tested some of the AB rounds - he said they shoot very well at 1000m.
If you go and read what Gene and Richard are saying about the old M118 Special Ball in the M14 thread it is very interesting being as the M21 is still widely used (I pulled that thread up with a stupid but true story as the best one I could find on this forum about the M21 and Special Ball). The 173 grain Full metal Jacket Boat Tail bullet itself was made by Lake City or Frankfurt arsenal. The stuff was really great at extreme ranges well past the transition zone. Even if you could get the M118LR stuff to be stable at the same distances the hollowpoint is not going to expand so expansion is not a consideration. Very few people do well with a 1/3 inch diameter hole through them so the FMJ BT was just as good as any other style bullet at those ranges.

It would be interesting to compare the shape of the Berger bullet with the 173 SB but I am sure Bryan L changed the nose profile in order to get a G1 of 0.5 but I bet the boat tail is the same
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Old 04-05-2011, 13:43   #14
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I think the price is pretty fair as well. My brother in law shoots, .257 weatherby Mag. It's around $70 a box! So far I've been doing well w/ 168g rounds, but then I also have only shot out to 650 yards.
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Old 04-06-2011, 06:39   #15
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Originally Posted by Buffalobob View Post
If you go and read what Gene and Richard are saying about the old M118 Special Ball in the M14 thread it is very interesting being as the M21 is still widely used (I pulled that thread up with a stupid but true story as the best one I could find on this forum about the M21 and Special Ball). The 173 grain Full metal Jacket Boat Tail bullet itself was made by Lake City or Frankfurt arsenal. The stuff was really great at extreme ranges well past the transition zone. Even if you could get the M118LR stuff to be stable at the same distances the hollowpoint is not going to expand so expansion is not a consideration. Very few people do well with a 1/3 inch diameter hole through them so the FMJ BT was just as good as any other style bullet at those ranges.

It would be interesting to compare the shape of the Berger bullet with the 173 SB but I am sure Bryan L changed the nose profile in order to get a G1 of 0.5 but I bet the boat tail is the same
Bob:

Took a look and it is marketing more so than anything else in my opinion. 7% improvement in BC? Show me how and prove it equates to a significant improvement of performance at those 'extended ranges'. Close down the tip and you will get four or five percent without any other change to the design.

What I find as being somewhat deceptive is the marketing. The marketing inferrs that because the numbers indicate 7% improvement in BC that one will see a 7% improvement at 'extended ranges', 'Improvement' "performance', and 'extended range' are vague and misleading when the implication is a significant improvement over what already exists.

One selling point is the length of the bullet but one can seat longer bullets deeper to feed from a magazine too and with the .308 it doesn't mean a thing where in other cartridges, increasing seating depth may mean dangerous pressures. The .308 is pretty forgiving.

I also read the SWAT article and they claimed 16 FPS per inch of barrel lost under 20" but only went down to 18". That by no means is enough information to make any conclusions but like most rags, they imply which is intellectually dishonest. Some cartridges need every foot per second of speed they can get and others don't. For SWAT purposes they don't need a 30" barrel. For Palma purposes given the rules of the sport plus the technology of today, one needs that barrel length to get speed.

The plus side is the brass is great and I am sure the bullets are just fine. Two dollars a shot is appalling for us who handload but for guys who don't or want to stock up on brass, the price really isn't bad at all. More power to Litz on this. No doubt he designed the bullet and no doubt the bullet is as good as any other top end 175 grain .30 caliber match bullet on the market.

However, maybe the real key to this discussion isn't technology or design but rather 'market'.

Gene
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