Jamie Young
New member
What bullet design improves upon a well balanced Boat tail bullet? What is Moly Coating? That only affects the bullet while traveling threw the rifling right? What is the most efficient bullet design out there?
What's better than a Boat tail?
- Thread starter Jamie Young
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Well, first of all, with the exception of aerodynamics, Boat-tail bullets are pretty bad.
They are more expensive, can have a tendency to be less accurate, and tend to wear barrels worse than flat-base bullets. Unless you really have a need to reach way out there, you're probably better off without boat-tails.
Moly coating involves coating the bullet with very fine molybdenum disulfide powder and usually with some sort of fixative to keep it from wearing off easily. Moly is very slick and will stick to steel to form a very thin, very hard, very slick coating. The idea is that the moly coating on the bullet coats the bore and prevents metal fouling. The jury is still out on this one. Some swear by it, others at it. From what I've seen in tests, it does coat the bore and can reduce metal fouling somewhat. It also tends to make velocities a bit more consistent. I've also seen some tests which indicate that moly can be slightly hygroscopic (attracts water) and can lead to rusting in the bore. Personally, I don't think there's enough benefit to go through the hassle.
The most efficient bullet design, theoretically, is a teardrop shape with the pointed end trailing. Unfortunately, that's not practical for various reasons.
There is a magazine called Precision Shooting that you might hunt down and subscribe to if this sort of stuff interests you.
Good shooting,
John
They are more expensive, can have a tendency to be less accurate, and tend to wear barrels worse than flat-base bullets. Unless you really have a need to reach way out there, you're probably better off without boat-tails.
Moly coating involves coating the bullet with very fine molybdenum disulfide powder and usually with some sort of fixative to keep it from wearing off easily. Moly is very slick and will stick to steel to form a very thin, very hard, very slick coating. The idea is that the moly coating on the bullet coats the bore and prevents metal fouling. The jury is still out on this one. Some swear by it, others at it. From what I've seen in tests, it does coat the bore and can reduce metal fouling somewhat. It also tends to make velocities a bit more consistent. I've also seen some tests which indicate that moly can be slightly hygroscopic (attracts water) and can lead to rusting in the bore. Personally, I don't think there's enough benefit to go through the hassle.
The most efficient bullet design, theoretically, is a teardrop shape with the pointed end trailing. Unfortunately, that's not practical for various reasons.
There is a magazine called Precision Shooting that you might hunt down and subscribe to if this sort of stuff interests you.
Good shooting,
John
trapshooter
Moderator
1. Nothing that I've ever heard of.
2. Molybdenum sulfide. Makes 'em slick. Clogs barrel. Totally unecessary, except for bench rest shooters who use it. Barrel makers hate it, mostly. (I know. It doesn't make sense).
3. I only know one way to find out for sure, and that's test them yourself. Anyone who makes bullets always has the best design, just ask 'em. Alternatively, ask around for what works in a given caliber/gun, or find out what the teams who won Camp Perry shot. May not be "the best design", but from a practical "best" point of view, you won't miss the mark by much.....
Unless I misunderstood your question in this regard, in which case, the answer is the standard (G1) bullet drag model . Closest real thing is the .50 BMG FMJ boattail. (If memory serves). Always a question. I'm too lazy to walk into the garage to the bench and dig out the ballistics crap, but if you have almost any lrecent/decent reloading manual, most all have good discussions in the sections on exterior ballistics.
PS - I forgot the most important thing, which John didn't. Best for what? Doh!
2. Molybdenum sulfide. Makes 'em slick. Clogs barrel. Totally unecessary, except for bench rest shooters who use it. Barrel makers hate it, mostly. (I know. It doesn't make sense).
3. I only know one way to find out for sure, and that's test them yourself. Anyone who makes bullets always has the best design, just ask 'em. Alternatively, ask around for what works in a given caliber/gun, or find out what the teams who won Camp Perry shot. May not be "the best design", but from a practical "best" point of view, you won't miss the mark by much.....
Unless I misunderstood your question in this regard, in which case, the answer is the standard (G1) bullet drag model . Closest real thing is the .50 BMG FMJ boattail. (If memory serves). Always a question. I'm too lazy to walk into the garage to the bench and dig out the ballistics crap, but if you have almost any lrecent/decent reloading manual, most all have good discussions in the sections on exterior ballistics.
PS - I forgot the most important thing, which John didn't. Best for what? Doh!
Jamie Young
New member
I've got a book on Reloading but I have to take in the Ballistic Info in Baby Steps. I thought the Boat Tail had the least bullet drag and stayed up longer due to that? I'm talking more Aerodynamics I guess.
Another question:
When bullets drop back under 1150fps, do they really get wacked from behind by the Sound Barrier shock wave? And they can start to tumble? Fact or Fiction?
Another question:
When bullets drop back under 1150fps, do they really get wacked from behind by the Sound Barrier shock wave? And they can start to tumble? Fact or Fiction?
Mike Irwin
Staff
"...and tend to wear barrels worse than flat-base bullets."
First I've ever heard that claimed.
What's there too it?
First I've ever heard that claimed.
What's there too it?
trapshooter
Moderator
Yep. Boat tails have less drag. Due to turbulence around the base of flat-base bullets that the boat-tail reduces. (Assuming otherwise identical bullet shape/size etc.)
There isn't any set fps where bullets transition the sound barrier, depends on altitude, temperature, and humidity. However, it does happen (assuming bullet is fired to a sufficiently elevated LOS so that it doesn't impact the dirt before it slows down this much). Also, bullet does this twice. Once on exit from barrel, and again down range. On exit, wave front passes length of bullet front to rear. Reverses procedure downrange. Depending on center of gravity, spin stabilization (and probably other factors that I can't recall), a bullet may or may not remain stabilized after this downrange transition. This is why twist is important. Ogive (sectional radius(?) of the pointy end) depends on caliber/length/mass, and will move the cg around, and thus affects stability also.
Bullets, without spin stabilization, are inherently unstable. (Smoothbore sabotted tank rounds have fins for this reason). And bullets still 'wobble', even with the proper amount of spin. The better ones just wobble less. Boattail bullets don't stay up longer, they just travel further in the same time given same velocity, due to decreased drag. All bullets of equal weight drop at the same rate, if drag is not a consideration. What this means is, if you shoot a gun and drop a bullet at exactly the same time, both bullets hit the ground at the same time. The one you shoot just hits way far away no drag, on either, of course, like in a vacuum).
Bullet makers have arcane ways of measuring ballistic coefficient, which is a measure of a bullets relative similarity to the G1 drag model. The nearer this number is to 1, the closer a bullets drag performance approximates that of the G1 model. Basically, they shoot a bunch at the same velocity, and compare drop at various ranges to the drop of the G1, at standard temp, press and humidity. BC is thus a statistical representation of the results of these tests in relation to the G1 theoretically 'perfect' bullet.
In the latest Sierra manual, they go so far as to give three different BC's at different ranges, as the bullets perfomance degrades downrange, and it's effective BC is lower.
I hope this is what you are looking for, and I hope I'm right. Thsi is my own layman's understanding of what all this stuff means. At some point, when they throw the calculus at me, I just take what they say on 'faith'.
There isn't any set fps where bullets transition the sound barrier, depends on altitude, temperature, and humidity. However, it does happen (assuming bullet is fired to a sufficiently elevated LOS so that it doesn't impact the dirt before it slows down this much). Also, bullet does this twice. Once on exit from barrel, and again down range. On exit, wave front passes length of bullet front to rear. Reverses procedure downrange. Depending on center of gravity, spin stabilization (and probably other factors that I can't recall), a bullet may or may not remain stabilized after this downrange transition. This is why twist is important. Ogive (sectional radius(?) of the pointy end) depends on caliber/length/mass, and will move the cg around, and thus affects stability also.
Bullets, without spin stabilization, are inherently unstable. (Smoothbore sabotted tank rounds have fins for this reason). And bullets still 'wobble', even with the proper amount of spin. The better ones just wobble less. Boattail bullets don't stay up longer, they just travel further in the same time given same velocity, due to decreased drag. All bullets of equal weight drop at the same rate, if drag is not a consideration. What this means is, if you shoot a gun and drop a bullet at exactly the same time, both bullets hit the ground at the same time. The one you shoot just hits way far away no drag, on either, of course, like in a vacuum).
Bullet makers have arcane ways of measuring ballistic coefficient, which is a measure of a bullets relative similarity to the G1 drag model. The nearer this number is to 1, the closer a bullets drag performance approximates that of the G1 model. Basically, they shoot a bunch at the same velocity, and compare drop at various ranges to the drop of the G1, at standard temp, press and humidity. BC is thus a statistical representation of the results of these tests in relation to the G1 theoretically 'perfect' bullet.
In the latest Sierra manual, they go so far as to give three different BC's at different ranges, as the bullets perfomance degrades downrange, and it's effective BC is lower.
I hope this is what you are looking for, and I hope I'm right. Thsi is my own layman's understanding of what all this stuff means. At some point, when they throw the calculus at me, I just take what they say on 'faith'.
rugerfreak
New member
Another question comes to mind---since I have a new rifle.
Would it be better to break in the barrel with coated or uncoated bullets??? Moly-coat that is.
Would it be better to break in the barrel with coated or uncoated bullets??? Moly-coat that is.
trapshooter
Moderator
Mike Irwin
maybe it's because us paper-punchers are always trying to cram more powder in around the extra space at the boattail.
maybe it's because us paper-punchers are always trying to cram more powder in around the extra space at the boattail.
Art Eatman
Staff in Memoriam
The boat-tail will give the flattest trajectory, but it doesn't show up very much inside of around 400 yards. Roughly. The difference is significantly notable out beyond 600 yards and more.
When you ask about "efficient", it makes a difference whether it's varmint hunting or medium game. It's a whole 'nother world if you're talking dangerous game. Still another if shooting at targets is the game.
Quick and dirty: Varmint bullets should come apart easily. Medium game bullets should expand but stay pretty much in one piece. Dangerous game bullets should punch through heavy hide and bone and make a large and long wound channel.
Target bullets are very precise in the thickness of their jacket material and the density of the core. The assembly process is also a precision deal. Overall, maximum uniformity of weight and shape.
Hope this helps,
Art
When you ask about "efficient", it makes a difference whether it's varmint hunting or medium game. It's a whole 'nother world if you're talking dangerous game. Still another if shooting at targets is the game.
Quick and dirty: Varmint bullets should come apart easily. Medium game bullets should expand but stay pretty much in one piece. Dangerous game bullets should punch through heavy hide and bone and make a large and long wound channel.
Target bullets are very precise in the thickness of their jacket material and the density of the core. The assembly process is also a precision deal. Overall, maximum uniformity of weight and shape.
Hope this helps,
Art
trapshooter
Moderator
rugerfreak
I wouldn't use moly. But that's just me. The barrel guys (at least one, as I recall) will void thier warranty if you use the stuff.
But I bet that someone will say exactly the opposite, and they might be right.
If you do use moly coated bullets, I would clean it frequently. As Mr. Irwin says, Precision Shooting is a good resource for more info on the pros, cons, and how to's of using them.
I wouldn't use moly. But that's just me. The barrel guys (at least one, as I recall) will void thier warranty if you use the stuff.
But I bet that someone will say exactly the opposite, and they might be right.
If you do use moly coated bullets, I would clean it frequently. As Mr. Irwin says, Precision Shooting is a good resource for more info on the pros, cons, and how to's of using them.
trapshooter
Moderator
In reference to...
Art Eatman's post.
That's practical knowledge, which beats theory any day.
Art Eatman's post.
That's practical knowledge, which beats theory any day.
DAVID NANCARROW
New member
So far as the bullet's flight, the most efficient is the VLD, or very low drag. It combines a very streamlined ogive (front end) with a boat tail. The boat tail is used to minimize the airflow disruption during trans sonic speeds. When the bullet is supersonic, the primary location of drag is the nose, and under the speed of sound (1080 fps, give or take local air density), the main location of drag is the back end, caused by air becoming turbulent after passing over the length of the bullet. The more pointed you can make the bullet nose, the less drag and the longer it will stay above Mach 1.
Boat tailed bullets have been accused of bore erosion due to swirling of the expanding gasses it causes because of its shape. If your shots are really long-400-500+ yards, a boattail might not drop quite as far as a flat base spitzer, but within 100-150 yards, you might be impressed as to the accuracy of a round nosed bullet in comparison, but it also illustrates why round nosed bullets aren't used for long range shooting these days-the bluff nose slows down quickly, which is why there isn't a whole lot of difference is speed between a 30-30, 35 Rem, or any of the others at 200 yards or so.
Boat tailed bullets have been accused of bore erosion due to swirling of the expanding gasses it causes because of its shape. If your shots are really long-400-500+ yards, a boattail might not drop quite as far as a flat base spitzer, but within 100-150 yards, you might be impressed as to the accuracy of a round nosed bullet in comparison, but it also illustrates why round nosed bullets aren't used for long range shooting these days-the bluff nose slows down quickly, which is why there isn't a whole lot of difference is speed between a 30-30, 35 Rem, or any of the others at 200 yards or so.
trapshooter
Moderator
Well, now I've definitely learned at least one new thing, today. I had never heard that.
(I still like my 'more powder' rationale though, even if it is made up BS.
)DAVID NANCARROW
New member
Trapshooter; just how much powder can you pack around that boattail LOL!
The 'reference bullet' used to calculate ballistic coefficients isn't a perfect bullet. It's possible to make bullets with ballistic coefficients larger than 1. I think some commercially available .50 BMG bullets meet that criteria.
Artillery shells typically have ballistic coefficients much larger than 1.
"boat-tail bullets are pretty bad."--I overstated my case. They're not pretty bad, what I should have said was that while they only have one advantage, they offer several disadvantages .
The easy way to think about the bore erosion statement is to visualize what the expanding gases do when they encounter a boat tail. The shape of the bullet tail forces the gases outward toward the bore. This increases blow by and is generally harder on the barrel. Flat base bullets have more of a tendency to seal the bore since the base can actually expand slightly to keep gases from escaping.
The accuracy issue has to do with the fact that the bullet's tail is still in the barrel and still being pushed around by the turbulent expanding gases after the bullet's bearing surface is free of the rifling. Flat base bullets let go of the rifling AS they leave the bore.
BTW, all of these negative effects are minor. Still, unless you're going to take full advantage of the long-range potential of the boat-tail's aerodynamics, you're paying the tradeoffs without getting the benefit.
Artillery shells typically have ballistic coefficients much larger than 1.
"boat-tail bullets are pretty bad."--I overstated my case. They're not pretty bad, what I should have said was that while they only have one advantage, they offer several disadvantages .
The easy way to think about the bore erosion statement is to visualize what the expanding gases do when they encounter a boat tail. The shape of the bullet tail forces the gases outward toward the bore. This increases blow by and is generally harder on the barrel. Flat base bullets have more of a tendency to seal the bore since the base can actually expand slightly to keep gases from escaping.
The accuracy issue has to do with the fact that the bullet's tail is still in the barrel and still being pushed around by the turbulent expanding gases after the bullet's bearing surface is free of the rifling. Flat base bullets let go of the rifling AS they leave the bore.
BTW, all of these negative effects are minor. Still, unless you're going to take full advantage of the long-range potential of the boat-tail's aerodynamics, you're paying the tradeoffs without getting the benefit.
one thing, maybe two:
if the flat end is supposed to be on the outside, and the pointy end on the inside, of the case, then why are all the fancy rocketships we send into outerspace equipped with pointy ends out?
Transsonic bullets shoot better with flat based out, cause it does more damage, and they diesel less. Supersonic bullets fly better pointy end out, cuz it's aerodynamically superior.
I've heard the boat-tail/flat base discussion long enough. Yes there is a theory that the flat base (Nosler Partition) will seal the bore surface better and a whole lot more technical info we need not deal with, and I've heard boat-tails erode throats quantitively more than others. Based on highly recommended advice on both accounts, I call BS. There IS NO hard evidence that a boat tail erodes more than a flat base. Period. You can get negative evidence from either situation wherever you are lookin'.
later
if the flat end is supposed to be on the outside, and the pointy end on the inside, of the case, then why are all the fancy rocketships we send into outerspace equipped with pointy ends out?
Transsonic bullets shoot better with flat based out, cause it does more damage, and they diesel less. Supersonic bullets fly better pointy end out, cuz it's aerodynamically superior.
I've heard the boat-tail/flat base discussion long enough. Yes there is a theory that the flat base (Nosler Partition) will seal the bore surface better and a whole lot more technical info we need not deal with, and I've heard boat-tails erode throats quantitively more than others. Based on highly recommended advice on both accounts, I call BS. There IS NO hard evidence that a boat tail erodes more than a flat base. Period. You can get negative evidence from either situation wherever you are lookin'.
later
DAVID NANCARROW
New member
:
It's called aerodynamics.
:
Boattails will usually fly farther than a flat base bullet because of less drag. A flat nosed bullet will open up at lower velocities assuming similar construction. Have no idea of what diesel has to do with a bullet, unless you just shot the gas pump.
And there is hard evidence as to erosion in barrels despite what you think. Is it significant? I don't think so, but its there just the same.
The boat tail is a compromise, just like the other designs, none of which is perfect. Thats one of the reasons I suspect that several shapes are available. Boat tails are more expensive because they are more complicated to manufacture, but they have their place
After just a quick scan of this thread .... & a quick input ....
The most efficient bullet design is a hollow point boat tail - as far as areodynamics go. Barnes does have a machined .50 cal "sharp tip" wasp-waist that defies some things we "knew."
"Efficient" here means only that the bullet has the best "opportunity" to fly as straight as possible & with the least amount of drag. What it does when it gets there is really beyond what the question was. That's a whole 'nother ballgame.
Boat tails don't wear out the bore any faster than flat based bullets, nor do they necessarily experience better accuracy - your rifle will do that - some do, some don't "like" boat tails & that can vary depending on load, bullet, & yada ... reloading's a science, but still an art .... reqiures much experiementing to determine what works in your rifle.
If boattails suck, why is most every militry loading one?
All things being equal, a botatail will deliver a tad more velocity at target & since velocity is squared re ft lbs computations, the ft lbs delivered is higher.
Much more to it though regards "the best," or "most efficient." & much of that depends on your rifle, the bullet weight, the velocity, & expected terminal "request."
You really do have to ask a better question when us "psychos" start to anal-lyze" this stuff ...
& BTW, Moly's great, except for those that hate it.
The most efficient bullet design is a hollow point boat tail - as far as areodynamics go. Barnes does have a machined .50 cal "sharp tip" wasp-waist that defies some things we "knew."
"Efficient" here means only that the bullet has the best "opportunity" to fly as straight as possible & with the least amount of drag. What it does when it gets there is really beyond what the question was. That's a whole 'nother ballgame.
Boat tails don't wear out the bore any faster than flat based bullets, nor do they necessarily experience better accuracy - your rifle will do that - some do, some don't "like" boat tails & that can vary depending on load, bullet, & yada ... reloading's a science, but still an art .... reqiures much experiementing to determine what works in your rifle.
If boattails suck, why is most every militry loading one?
All things being equal, a botatail will deliver a tad more velocity at target & since velocity is squared re ft lbs computations, the ft lbs delivered is higher.
Much more to it though regards "the best," or "most efficient." & much of that depends on your rifle, the bullet weight, the velocity, & expected terminal "request."
You really do have to ask a better question when us "psychos" start to anal-lyze" this stuff ...
& BTW, Moly's great, except for those that hate it.
"if the flat end is supposed to be on the outside, and the pointy end on the inside, of the case, then why are all the fancy rocketships we send into outerspace equipped with pointy ends out? "
Rocket is driven by expanding gasses exausting from the rear. The exhaust streamlines the shape somewhat while under power and in the atmosphere. Outside of the atmosphere it matters not.
Sam
Rocket is driven by expanding gasses exausting from the rear. The exhaust streamlines the shape somewhat while under power and in the atmosphere. Outside of the atmosphere it matters not.
Sam
Alexis Machine
New member
A finned sabot round with a gas-bleed base is better than a boattail. To bad nobody makes one smaller than 105mm.
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