On another thread someone said that Jack O'Conner said that "gas leaks around boat tailed bullets erode the bore more than flat based bullets."

I have never heard this before. Is there any truth to it? It's hard for me to believe that using boat tail bullets has much negative effects on the barrel. I shoot a lot of them, especially where faster velocities are involved. The faster velocities would seem to be more of a problem on the barrel than the "gas leaking around boat tail bullets."

Old wives tale, long disproved, but still keeps comming back to life.
Tell me who said it so I can visit them with a wooden stake and kill this myth once and for all...

Now the background...
YEARS ago the cartridge for the 30caliber service rifle was laoded with a boat tailed bullet and at the same time there were some other issues with bore degradation.

This was largely a result of the switch from mercuric primers
to "Corrosive" primers which caused corrosion and so required a more vigorous (near ritualistic) cleaning.

If the muzzle crown or more on point, the rifling lands at the muzzle crown, if they were dammaged the rifle would suffer accuracy degradation.
the funny thing is that boat tailed bullets are more sensitive to muzzle condition than flat based bullets, so ANY dammage to the muzzle lands is much more likely to be noticed when shooting boat tailed bullets.

Later the service cartridge was changed, the "M2" ball round used a 150gr bullet, but that was for a different reason...
Shooting the heavier boat tailed bullet M1 service load as a steady diet in the M1Garand can and eventually will "Batter" the action and in paricular can even bend the operating rod...

Yes target loads with heavy bullets are used all the time in garands but at reduced pressure and velocities.

So no boattails don't cause bore wear.
But some rifles don't shoot them well.

I always load boat-tails first if the rifle won't shoot them next step is to have the rifle recrowned.


AD

quote:

Originally posted by Red C.:
On another thread someone said that Jack O'Conner said that "gas leaks around boat tailed bullets erode the bore more than flat based bullets."."

As Allan said

.

Yeah, lets say this is right....

how much reduced barrel life are we really talking???

I prefer flat based bullets, but at the same time, I wouldn't be using them strictly because I was thinking I was dramatically increasing the throat life on my barrel...

Fact or fiction, I can see it have a major impact either way in the real world, where it takes most folks tons of time to wear out a barrel...

/

Alf,

I wasn't questioning your end of the discussion... my real point was that it really shouldn't matter in rifles...

even in a varmint rifle that can have a barrel with a life span of a couple of seasons... I still don't think you are reducing the life of the barrel substantially enough to be concerned about it...

The original question: Does shooting BT bullets increase bore erosion?" The answer has to be YES or NO.

And the nitpickers are off and running.......
"I can define "is" finer than you!!!!! so neener, neener, neener."
In the REAL world of hunting rifles, where the nitpickers seldom tread, you will find no discernable difference between the two.

/

Perennial old wives tale.

Alf, thank you. Now I can sleep at night.

Have any tests been done to establish whether or not boat tails do erode more than flat bases?
Speculation sucks..

Don

Hey Red, No! Not at all, for anyone who shoots their firearms with consideration to not "over-heating" the barrel. Some of the folks that shoot Gophers and P-Dogs have the potential to destroy a barrel in a short amount of time "if" they do not pay attention to how hot the barrel becomes. And that can be with either Boat Tail or Flat Base Bullets.

It is important to remember a lot of the information from the O'Conner, Keith and Ackley eras is a bit dated. Some of it is still valid, accurate and has never been improved upon. And some has been found to be a product of slightly incorrect speculation.

So, which ever Design Bullet your rifle shoots the best, with consideration given to a proper structural Design for the task, is the one you should use. No need to be worried about "wearing out a barrel quicker" with either Flat Base or Boat Tail Bullets.

Best of luck to you.

quote:

Boat tail bullets erode bore more than flat base bullets?

No they do not.

This has been hashed out on two previous threads and no proof has been presented that boat tails are worse than flat base bullets for erosion.

The big culprits are under size bullets, rate of fire and volume and type of propellant.

If you think otherwise, present proof not rumour.

Unless you qualify the answer with a bunch of details that are irrelevant to typical sporting rifles the answer is no.

I've so far "shot out" two barrels on sporting rifles.
Perfectly good essentially identical factory tubes on a 25-06
The first barrel IIRC "went off" in a bit under 1800rounds (~ 4 years), the vast majority of these were 90gr Sierra boat tails the other barrel went away in around 1200rounds (<2 years) that one was fed mostly 75gr Hornady Flat base bullets.

Neither barrel was used for prarie dog shooting.
I won't discuss the barrel I incinerated on a mini14.
you just KNOW what that was all about
(DIE SODA CAN, DIE!!!!)

I don't believe the bullet base shape had any effect on the barrel's demise.

what did cause them to wear out was just how much burning IMR4350 and IMR4831 was exhausted through them.... that enormous flash when 62grains of IMR4831
pushes that 75gr hollow point downrange at 3800fps
tells you something bad is happening inside the barrel...

The shape of the base of that copper clad cork that is trying to hold the angry genie back is hardly relevant in the greater scheme of things.

I doubt that given identical loads it would change the total number of rounds I could have shot through either rifle barrel by more than 50 rounds.

AD

In JOC's case, his barrels probably wore out quicker due to the 75,000+ psi loads he was running for years. He probably blamed it on a boat-tail bullets that were shot late in the life of the barrel.

I/

logic says that a boattail bullet traveling at 3000fps is in a 24" 30-06 barrel actually travels 20.65" inches from case mouth to muzzle. It is doing that travel in .0005736 seconds.

The government is likely using the same scientific principles that proved in 1942 that an atomic bomb was impossible to build, and in 1956 proved conclusively that a bumblebee was too un-aerodynamic to fly.

I would suggest that the velocity and type of powder have more to do with erosion than bullet base shape. As an example, the military found in the early 1960's that switching to a ball powder greatly increased accuracy and barrel life, and reduced fouling in the M-16 gas system. Prior to that discovery, the military had many detractors and few supporters of the M-16.
Stick powders erode barrels faster, and that is the most likely culprit.

Rich
DRSS
Knowledge not shared is knowledge lost...

I think the issues confronting Automatic weapons are very different than those confronting bolt action rifles.

Let's face it a single M16 or M4 carbine can spit out more rounds in a single afternoon in Mosul than my bolt action 223 has since it left the factory in 2004.

I have yet to fire more than 30rounds in a single day with it

I'm not real worried about the difference between boat tails and flat bases and when bore wear does become a concern
I have ways of dealing with that too...

I have an action wrench, a barrel vise and a lathe.
I also have a telephone and Dan Lilja's phone number.

BTW, the takeoff barrel? I can always run a 22-250 reamer into it and screw it onto the next used 22-250 or 243 that turns up with a burned out barrel at my favorite "Toy store"

AD

quote:

they all concur, boattailing of a projectile increases gas blow by and changes boundry flow conditions in gas mass so that more heat is absorbed in the barrel. What is also apparent is that this erosion is not throat erosion but erosion close the muzzle end of the bore.

I have never seen a hunting rifle with erosion at the muzzle that exceeds erosion at the throat. If this is true in the context of what the military do, how is it applicable to our hunting rifles?

quote:

if a shadowgraph is taken at high speed of bullet exit from muzzle

quote:

The more friction there is the tighter the fit and less powder can blow by ?

How do you tie these two together? One has nothing to do with the other.

However:

quote:

the jacketed bullet shows more inertial upset and should by all accounts give better obutration that a solid monometal bullet wich has more radial stiffness? Thus less blow by?

Only if the mono is under size for the barrel.

quote:

This Obturation issue is fact because pressure studies have shown that "soft" bullets that upset relatively more than "hard" bullets actually induce greater friction than the so called hard bullets.

This is true.

quote:

The more friction there is the tighter the fit and less powder can blow by ?

Not true. Ask any engineer - A seal is a seal and friction has nothing to do with it.

Two schools of thought on this subject .

School one ; Don't fire the weapon and NO erosion will occur !.

School Two ; Get a bore with no rifling or plug your rifling grooves up , because gas erodes those also .

For the rest of us who are now out of school , who really cares !?. Extreme velocity loads contribute to erosion to . So , Buy a new barrel when yours wears out !.

Shoot Straight Know Your Target . ...

quote:

There is even a study on what the most beneficial boat tail angle is to mitigate the problem.

This study was underataken because there was an attempt in 1967 ? to use FB bullets in the 5.56 in a attempt to mitigate boattail induced erosion, this failed because of accuracy problems so they studied what angle of boattailing would give the least amount of erosion if you were going to boattail the bullet. I believe that 9 degrees was found to be the least amount.

Alf,

An interesting observation with reference to the degrees at which the boattail angle runs and thus the deeper that section is between the bullet and the bore. The question of the burning flame in the "designed cavity" was raised before as a factor, but this hypothesis was shrugged off before here on AR by some. Alf could you perhaps expand on this theory of the angle a bit more or site some more pertinent details for us. Does this study make comments about a worst position that was encountered?

There is indeed a big difference in boattails that we see in various bullet designs and shapes. Some are sharper and longer, some short and shallow and anything in between. Here is an example of a fairly unique boattail not commonly seen in an attempt to shift the COG point forward, and as a result the angle is way beyond the 9 degrees. I can see the good in that the bullet is better balanced, making it easier to stabilize, but then you may pay a price elsewhere.



Warrior

Erosion of the bore at the muzzle end of a barrel is a problem with high rates of fire. This does not apply to hunting rifles. Boat tail angle therefore has nothing to do with throat erosion. Alf, will you please tell the village idiot that this is so, so that he can stop trying to find imaginary problems with GSC boat tail bullets. It is tiresome when he misreads (misunderstands deliberately?) content and then makes mistaken assumptions, trying to start an argument he does not understand in the first place.

Examples:

quote:

An interesting observation with reference to the degrees at which the boattail angle runs and thus the deeper that section is between the bullet and the bore.

The angle of a boat tail does not determine the length of the boat tail. A 4 degree boat tail can be longer or shorter than a 7 degree boat tail. His thinking is muddy.

quote:

Here is an example of a fairly unique boattail not commonly seen in an attempt to shift the COG point forward, and as a result the angle is way beyond the 9 degrees.

Only he would try to assign an angle to a curved dimension.

quote:

I can see the good in that the bullet is better balanced, making it easier to stabilize.

Shifting the cg forwards, lowers the stability factor, making the bullet less stable in flight.

Warrior,
I have said before and I will say it again. As long as you flap your mouth about GSC products and as long as you pursue your agenda of finding imaginary faults with our bullets, I will point out that you are a ballistic buffoon. Incapable of learning, pretending to be something you are not and interested only in your agenda of slander of and fault finding with GSC Bullets.

Gerard,

I have asked questions. I did not make statements or slanderous remarks as you hint. I said it is a unique design. Did you miss that. I did not infer that a curve is equal to an angle. It is so obvious.

And your compliments never stop - you just cannot have a straight conversation, you have to belittle.

Warrior

quote:

I have asked questions. I did not make statements or slanderous remarks as you hint.

I see. So as long as the derogatory remark or implication is in question form, it is not derogatory. Therefore: "Is Warrior a ballistic buffoon?" has no derogatory meaning. Thanks for clearing that up, I will use it in future.

quote:

I said it is a unique design. Did you miss that.

No, I did not miss it. What is your point in bringing that up?

quote:

I did not infer that a curve is equal to an angle.

No, you said that the curved surface has an an angle of more than 9 degrees.

quote:

It is so obvious.

No it is not. The flow over a curved surface is different to that which flows over a straight boat tail. As you are so fond of saying: "Did you miss that?"

You make mistakes so fast, it is difficult to keep up. I am done here for now, feel free to continue making mistakes, I will deal with them later.

Gerard,

You are creating smoke again. We are discussing boatails no matter what the curve or the angle if you want to be predantic. Any curve deviates at an angle any way from a straight line, not so? I said your design is unigue, just like your 230 gr HV differs from your 260 gr HV bullet. So we have 2 unique designs here, even though they look similar. That is what we are trying to discuss here and to seek more pertinent information about, hence my question to Alf to give us the span of the observations done by the military study .... [(Source Technical report ARCCB-TR-98017 of the US army Research Development and Enginering centre Sept 1998. This paper cites a number of sources validating this issue )]

Very few things happen in isolation in ballistics, if you do too much of the one thing you rob something else in the system and somewhere in the middle we find the best trade-off. That may just be the case with boattails, grooves, driving bands, case body taper, slope of shoulder, length of neck, necking down large cases to smaller bores, and the list goes on, etc.

Here we have your 230 gr vs the 260 gr HV bullet, and yes they are very different, just as a host of other brands of different designs. Perhaps there is an interesting aspect here as to which one offers the most benefits or the least amount of drawbacks if you will.



So there are no faults, real or imaginary, just plusses and minusses and that is what we are trying to better understand; no more and no less. The only derogotary remarks that are being made comes from your own mouth !!!

Warrior

No one here has provided any back data or theory to support the statement that boat tails cause more erosion.
If you magnify a flat base bullet you will always find there is an edge radius or chamfer. The corner of the heel is never perfectly sharp. Thus there is always some angle between the bullet base and the the bore. This angle is always huge compared to the gas molecules. I have no idea why a gas molecule would act different when pushing into the intersection of a flat base and a barrel vs the intersection of a boat tail and the barrel. After all the intersection of both is huge in comparison to the gas molecule.

Hey VVarrior
Alf said

quote:

But the question was asked: Is there a difference between FB and BT bullets, no more no less in terms of bore wear? The answer is yes!

and he qualified it by adding

quote:

When you are dealing with machine guns or auto cannons like the typical 30 and 40 mm AA guns or then large bore guns where barrel wear is a reality from shot to shot it seems to be more pressing.

and further explained

quote:

What is also apparent is that this wear pattern is near the muzzle end of the gun and therefore is more thermal and mechanical wear related,

and also said

quote:

By intentionally comparing heat transfer to barrel steel by using obturating vs poorly obturating projectiles in a barrel it has been shown that the greater the blow by the greater the heat transfer to the barrel.

and even repeated

quote:

What is also apparent is that this erosion is not throat erosion but erosion close the muzzle end of the bore.

Gerard then said

quote:

The big culprits are under size bullets, rate of fire and volume and type of propellant.

If you think otherwise, present proof not rumour.

The proof presented imply that Alf is right. Boattails cause more erosion of a barrel interior near the muzzle if you are shooting a machine gun or an artillery piece. Alfs papers also show that Gerard is right if you are using a bolt action hunting rifle and not shooting it as fast as you can and overheating it like Shootaway does.

In internal combustion engine design one also relies on studies and experiments that have been done before. The danger is that a study and its results are applied to a situation without considering what is different from the study to the situation it is applied to now.

Spark plug cores contain copper because copper has the highest thermal conductivity of all metals. Lead has close to the worst thermal conductivity. It comes to mind to ask: Were the studies that Alf refer to made with copper bullets or with lead cored bullets? How does the ten times higher thermal conductivity of a monometallic copper bullet compared to a lead bullet affect the heat transfer patterns? Boattail or no boattail I think the copper bullet would be advantageous here. If Alfs studies were not made with copper bullets they do not apply to how copper bullets will affect this topic.

It has also been concluded by VVarrior that a question cannot be derogatory so there is no harm in asking:

Can VVarrior read?
Does he comprehend what he reads?
Why does he act stupid?
Is he driven by a dark obsession?
Does he wear a rug?
Why does he continue to make an of himself?

ireload2
Good point you make there.

Alf's request on another thread:

quote:

Springtrap

You accuse me of blowing bubbles on BT bullets ? Do you have an opinion on the subject ?

let us leave it be cause it dont pertain to this thread, bring it on to the BT and bore erosion thread I would be most interested to hear your point of view on BT's and erosion

One practical example, no military theories or whatever, plain field test reults:
Gerard's modified 22 x 64 shot close to 3000 shots with GSC boattail bullets at muzzle velocities ranging between 4400fps and 4700fps and yet no sign of excessive throat or barrel wear - rifle still shooting perfect.

You choose any of your rifles and do the same with flat base bullets, even if you can not nearly reach those muzzle velocities, and come back and tell us what your rifle's throat and barrel looks like.

Until then, hush baby, don't you cry (foul)!

Also, read carefully what Rat Motor posted above.

Throat erosion happens regardless of the rear shape of a bullet, as it is primarily caused by hot gas behind the bullet that washes over the throat area. Cartridges that are over-bore and require voluminous charges of powder, like the fastest 7 mm's and the .300's (not to mention the .30-378 Wby Mag), are going to erode throats and wear out barrels faster than more efficient cartridges.

The additional exacerbating factors are continuous rapid fire, the heat of explosion of the powder (flame temperature) and undersized bullets. Burning gases from nitrocellulose powders travel at about 5,300 fps, which is faster than what a bullet can travel as the gas must push the bullet down the bore and through the rifling overcoming the friction, and so velocity is reduced. Naturally one can expect that something profound must happen when the bullet exits. As the gases pushing the bullet through the barrel possess a greater velocity potential than the bullet does, the gas will blow past the bullet the very instant the bullet breaks seal with the muzzle at the crown. This "blow by" effect at the time of exit washes metal away over time. As the muzzle erodes, the gases start leaking around the bullet before it is really supposed to be free from the barrel.

Any irregularity in the way the gases leak past the bullet will have an effect on accuracy and that is why a perfectly square crown is so important for accuracy potential. The condition of the rifling at the muzzle and the crown have greater implications than a few thousandth's of wear at the throat.

The nagging question is to what extent does the angle of the boattail contributes to accelerated wear to both ends of the barrel and it is probably far far less than the way we abuse the barrel by picking over-bore cartridges, loading them to max, engaging in rapid fire. To add to this, we have the effect of undersized bullets and a boattail that is funneling the high-pressure gas between the bore and the bullet. Surely difficult to quantify without some controlled long duration tests by those that have set themselves the task to research the matter.

Warrior

The shocking truth of throat erosion in the .30-378 Wby Mag can be seen here ... http://www.accuratereloading.com/30378wmag.html

Warrior

If you can afford enough Boat tail bullets to wear out a barrel, you can afford a new barrel or a new gun.
I wouldn't worry about it and just shoot whatever bullet works best for ya.....

quote:

Originally posted by Gerard:

quote:

Boat tail bullets erode bore more than flat base bullets?

No they do not.

This has been hashed out on two previous threads and no proof has been presented that boat tails are worse than flat base bullets for erosion.

The big culprits are under size bullets, rate of fire and volume and type of propellant.

If you think otherwise, present proof not rumour.

I'm on Gerard's side on this issue.

/

Yeah, at last! Somthing must have woken you up out of your deep, icy cold winter sleep to say this, Alf:

quote:

It is more likely in my opinion that one would lose a barrel to throat erosion because of the total mass of slow buring powder than because of the effects of the BT

Now you must just get your 'well meaning' friend Warrior to understand the same as he still thinks along these next lines:

quote:

To add to this, we have the effect of undersized bullets and a boattail that is funneling the high-pressure gas between the bore and the bullet. Surely difficult to quantify without some controlled long duration tests by those that have set themselves the task to research the matter.

Sorry for you to get that done soon, may proof to be very difficult if not totally impossible

Finally, the SA guys got to the bottom of it, shoot your boattails and preferably the best on the market - GS Custom

Finally, the SA guys got to the bottom of it, shoot your boattails and preferably the best on the market - GS Custom [/QUOTE]

As touchy and defensive as the SA guys come across on the subject of GS custom bullets I do not plan to rush out and buy any.

quote:

ron williams
one of us

Posted 09 March 2008 18:11 Hide Post
Buy the best you can afford.

2000.00 dollars should get you a very fine outfit.


There are no fleas on the 9.3s

Whether it is iro rifles, reloading equipment or whatever you were referring to above, it is also applicable when it comes to bullets.

Practice what you preach!

/