The two statements I made and stand by are:

1. Throat erosion is accelerated if the dimensions of bullet and throat are such that gas escapes around the bullet and down the bore ahead of it.
2. Boat tail bullets do not cause more throat erosion than flat base bullets.

Every reference I have ever come across regarding throat erosion and boat tail bullets, military and otherwise, blamed the propellant and hotter loads for the erosion, not the style of bullet. Baottails tend to be used in conjunction with such loadings but are not the cause. Check it out, especially the smle saga.

What do others say?

quote:

Dan Lilja
...throat erosion was caused primarily by hot gases, not friction, and interestingly, that it may have been accelerated by an original throat diameter that was .0028" over bullet diameter. In theory, this allowed excessive amounts of hot gas to escape around the bullet and `burn' the throat even more. The crux of the experiment was that gas erosion and not friction caused the most wear on the throat and barrel.

In a lengthy article, dedicated to the subject of throat erosion, not one word is said about boattail bullets contributing to erosion.

quote:

From Shortmags.org:
A bullet that obturates (upsets) on impact with the rifling in your barrel to form a tight seal, thus minimizing the gas blow-by and premature throat erosion often attendant with monolithic and sold-base bullets.

There is a tendency with monometal and solid base bullet manufacturers to make under size bullets. This is detrimental to throat life. Once again a comprehensive article on throat erosion contains no reference to boattails as a cause.

A Norwegian website contains this interesting item:

quote:

Boattail vs. Flat-bottom Bullets: More matches have been won over the past 40 years with boattail bullets than any other kind. Military rifle cartridges are all loaded with boattail bullets. Nosier ballistic tips and Sierra boattails are excellent hunting bullets providing benchrest type accuracy. Because of bullet jacket thinness the ballistic tips should be limited to deer size game.
A myth that still exists is, boattail bullets will cause throat erosion earlier than flatbottom bullets. From government test results (Frankford Arsenal) and those conducted by manufacturers, accuracy will improve and be maintained up to 10,000 rounds using boattail bullets with proper cleaning, while flat-bottom bullet accuracy peaked at around 2,000 rounds and started to diminish by 5,000 rounds.

From the Long Range Hunting Forum:

quote:

I have seen same brand barrels act completely different as far as throat erosion goes. barrel steel varies from lot to lot, even the good stuff. There are several factors that can effect how fast teh throat erodes, is ball powder being used or stick powder? Is the rifle being cleaned with a bore guide?

What are the throat dimensions in the chamber? Stick powders tend to erode throats faster then ball powders on average because they are more physically abrasive and they tend to burn a little hotter then ball powders.

If a bore guide is not used, this will accelerate the wash out of the throat.

If the throat is loose, which on a custom rifle it had better not be but it is not uncommon, your throat will erode much faster then with a quality match grade throat cut 0.0002" to 0.0005" over bullet diameter.

This is because it allows much more gas to escape around the bullet and this gas basically acts like a blow torch on the throat.

For a 300 WM to have .070" throat erosion in only 700 rounds would be quite a bit with the care you have taken of the barrel. Still not unheard of depending on the factors listed above.

Your working pressure of your loads also has a great effect on throat erosion.

Having a 6 or 8 groove barrel will result in faster throat erosion then a 3 or 4 groove barrel.

There are alot of variables!!

Good Shooting!!

Kirby Allen

There are a lot of variables indeed, but not a word about boattail bullets!!!!

The glossary at Exterior Ballistics states:

quote:

Erosion: The wear, usually in the throat area of a barrel, caused by extreme heat and friction. Erosion occurs in all firearms but is aggravated by rapid fire, large case capacity, or the use of hotter burning powders.

So we see that it is important to seal the bore as fast and as effectively as possible. This may be a problem with some manufacturers but not with all. If anyone has evidence, other than hearsay, that boattails accellerate throat wear, I would like to see it.

Gerard,

Seeing that bullet to barrel seal is critical,If one was to combine your HV bands with a polygonal bore, would that offer any added advantage?..ie; (even better sealing and velocity) compared to more traditional groove barrels?

/

Woodjack,
I have never seen a bullet recovered after firing from a polygonal barrel. Polygonal barrels conform to the CIP/SAAMI specs for minimum and maximum bore and groove sizes, as far as I can establish. The shaft of an HV or FN bullet would then conform to the "bore" size of a polygonal barrel and the drive bands will be a fraction over the "groove" dimension for a good seal. That is the theory but I would like to see how it works out in practice. Anyone with a polygonal barrel rifle want some free bullets?

Alf, gas {pressure) leakage past the bullet is the difference between a "fast" and a "slow" rifle. A customer in Gauteng could not get halfway decent speed with our 40gr HV in his 22-250, until we established that his brand new barrel was about 90 micron (0.004") over size in the grooves. A max load barely broke 4050fps. He sent it back to the company who fitted the barrel and, when he got it back, he popped a primer out of the case on the first shot. He is not a very experienced reloader and once he backed off the load and worked up again, he now runs 4200 comfortably with less powder. Under size bullets (or over size barrels) reduces useful barrel life by a huge amount and should be avoided at all cost. The demon also feeds on itself. Once it starts, it advances rapidly.

Gas cutting erosion is not a factor in the big bores, which are not squad automatic weapons.

Those small bore hyper velocity varmint rifles, that Gerard's bullets make into plains game tools? No, not even there unless abusive barrel heating from fast fire and heavy use. If a cutting torch was blowing by the bullets to get to the lands first, it would melt the bullet.

Does not the primer blast move any bullet into the lands ahead of the burning powder?

Yes!

The .375 Weatherby freebore is only .0005" over bullet diameter.

Not a problem. Not much of the initial primer burp can get through there.

The notorious barrel burners have short throats and over-bore cartridge cases. That is where most of the cutting torch effect comes from, the burning powder and gas pushing the bullet.

This is my understanding of Mr. Gerard's torch comments.

If the base of the bullet exits the case mouth before the foward part of the shank enters the bore enough to seal, then gas will be blowing by the bullet through an increasingly smaller circular aperture until the bore is sealed. Hence the cutting torch analogy.

Does anyone know if the blast ahead of the bullet is propellent gas or just air? Seems like the cast bullet guys could answer this.

Does the bullet sit there, stuck in the lands but not bottomed out in the grooves, or "slowly" move foward while pressure is building, allowing time for gas to come through?

Does the burning rate of the powder have any measureable effect on gas cutting if there is gas cutting? I think Richard Lee claimed to get gas cutting on a lead .30-'06 bullet when using a pistol powder but not when using slower powder.

/

Gentlemen,

I have edited my above post numerous times due to confusion.

I hope that by asking questions I do not seem smart alecky.

It's just that I know only what I read about this subject and there seems to be conflicting info. For example, I read a magazine article several years ago where it was claimed that double based powders caused less throat erosion because the increased burn time resulted in lower temperatures because the burn was spread out longer through the bore.

?????????????????????????????

I greatly appreciate the contributions from you gentlemen on these subjects and have a self interest in this one. I'm wondering if using a very fast shotgun powder for cast bullet loads in .375 H&H will increase throat erosion, assuming a good bullet fit, length of shank and diameter? Sorry if this is too far off topic.

Rats, this post has been edited because I realize it's way off topic, I think.

/

quote:

If a cutting torch was blowing by the bullets to get to the lands first, it would melt the bullet. - RIP

RIP,

Seems quite logigal, especially if the bullet is made from a material that has a far lower melt temperature than steel, but you have already explained in a previous post that the first rush of gas ahead of the bullet is just some low temperature air, and it is by no means a cutting torch yet before the bullet engraves. The continous expanding gas is still in the process of heating up, and heating up fast, and is thus warmer by the time when the bullet is further into the barrel and the boatail bullet provides a wedge-shaped geomerty configuration for the hot gas to go into - between the bullet and the throat. It stands to reason that this condition cannot extend barrel life, but rather reduce it - exactly how much we do not know for sure, as it can vary from cartridge to cartridge (for eg, 7mm Muaser vs 7mm Rem Mag vs 7 mm STW)featuring different operating pressures and loads may also differ as to if they are mild or hot loads. When the base of the bullet does not fully expand and properly seal the bore, some erosion must take place. When an over-bore cartridge features a short throat in addition, it creates more pressure.

On another note about different flame temperatures and burn rates by virtue of the choice of powder for a particular caliber. Some powders burn hotter than others, and therefore they tend to burn the throat faster. Powders are compared or rated with what we call the "Heat of explosion" (HOE). Generally the lower it is, one can expect extended barrel life. For example, here are some powders that are used in the 9,3 x 62:

Varget .................... 4,040 kJ/kg
RL 15 ......................3,990 kJ/kg (used mostly in USA)
Vihtavuori N150 ... 3,780 kJ/kg (used by Lapua in their factory load)
S335 ..................... .3,710 kJ/kg
S365 ....................... 3,685 kJ/kg
S341 ....................... 3,660 kJ/kg (used mostly in SA)

In the above list, Varget is the hottest burning, and therefore the most likely to burn the throat faster. The second hottest being RL 15, etc. 'HOE' is sometimes also expressed as a BTU rate. [QuickLoad gives the "heat of explosion" for powders and there it is shown in units of kilojoules/kilogram. To convert that value to units of btu/lb, just divide by 2.3261]. Example: 58 grains of RL 15 is quite a popular load with a .366/286 gr bullet in the USA, and when it is compared with the same load in S341, which is quite popular in SA, then it is clear which powder has a milder effect on throat erosion.

However, we must bear in mind that HOE is just one factor of many. There are also other factors that work in tandem, such as the operating pressure and the burn rate. Operating pressure can be brought down in a particular cartridge with milder loads. Cartridge design dictates that a 7x57 will have lower pressure than a 7 mm Rem Mag, etc. The burn rate is an issue when we have to decide on a powder for a given caliber - it will differ from type of powder (single or double based) and make. Finally the amount of throat erosion due to a particular charge will depend on the temperature intensity and the time exposure.

Rapid fire is major culprit on the bench, but in the field you generally shoot 1 or 2 shots and the hunt is over. Over-bore cartridges are notoriously bad ito giving a long accurate barrel life, and that is why these cartridges are better equipped with tougher stainless steel barrels and competetive benchrest shooters replace their barrels as soon as they detect a widening group.

Chris

quote:

Gas cutting erosion is not a factor in the big bores,

Gas cutting happens whenever gas blows by between bullet and barrel, regardless of caliber. Most owners of large bore rifles do not regard it as a factor because such rifles do not see several hundred shots fired in a season, let alone several thousand in a season, as some medium and small calibers do. Regardless of the gun owner's position or outlook, it remains the responsibility of the manufacturer of a bullet to ensure that, if the bullet is used as recommended, unneccesary damage is not done to the system.

quote:

If a cutting torch was blowing by the bullets to get to the lands first, it would melt the bullet.

As for melting the bullet, erosion of the bullet does happen. It does not matter because a new bullet is used every time. You could wear out a bullet by firing it repeatedly through a new barrel every time. After enough of this, the bullet will be comprehensively stuffed but the heap of barrels will be pristine, having fired only one shot each.

The melting point of copper is around 1080 C while most steels are around 1500 C. However, the thermal conductivity of copper is much higher than that of steel and that is why spot welding tips and gas welding nozzles, that can be used to weld steel and even stainless steel, are made from copper. A rapid application of heat will raise the surface temperature of steel far mor rapidly than a surface of copper. We have supplied thousands of spot welding tips to a catalytic converter manufacturer. They are returned to us for refurbushing after thousands of welds were done with them. I have been using the same two copper gas welding nozzles in my oxy-acetylene gas welding handset for the past 10 years. They show wear but nothing like the steel they are used on. So, applying flame under pressure to a gap between bullet and barrel will have a far more detrimental effect on the steel than on the copper.

quote:

Does not the primer blast move any bullet into the lands ahead of the burning powder?

Quite correct and the higher the engraving pressure required to engrave the bullet (steel jackets and solid brass) the longer it takes to seal the bore because the bullet must be engraved at least the length of the throat before the barrel is sealed. If the bullet is under size for the groove diameter and monometallic, it does not seal at all.

quote:

The notorious barrel burners have short throats and over-bore cartridge cases.

True without doubt. Shorter throat = steeper throat angle = more resistance to engraving = slower passage through throat = more erosion before the barrel is sealed.

quote:

If the base of the bullet exits the case mouth before the foward part of the shank enters the bore

We must make a correction here. With bullets that have an ogive that meets the shank at barrel groove diameter, gas starts flowing past the bullet before the base exits the case mouth. The bullet resists engraving and this allows pressure to build in the case, the case neck expands and lets the bullet go.

quote:

"slowly" move foward while pressure is building, allowing time for gas to come through?

Essentially, yes, but more so with some bullet/throat combinations than with others. To a certain extent, it is a controllable variable.

quote:

the first rush of gas ahead of the bullet is just some low temperature air, and it is by no means a cutting torch yet before the bullet engraves.

Propellant gas escapes past the bullet as it transitions from rest to engagement of the rifling. The caption to the illustration from Lloyd Brownell's work states: "Cross section of forepart of fired cartridge at time of bullet start. Note annular area around bullet allowing gas leakage. Bullet floats on gas stream."

quote:

the boatail bullet provides a wedge-shaped geomerty configuration for the hot gas to go into

If anything, the larger surface area of copper exposed to the flame front with a boattail and the high thermal conductivity of copper, will lower the temperature. Erosion occurs when superheated gas flows over a surface at high speed and the smaller the gap it flows through, the more severe the erosion. Ask any welder. The gas in the "wedge shaped" corner that you fret about where the gas "go into" is stationary relative to the bullet. No flow. Relative to the barrel, the flow is the same with a flat base as with a boattail.

quote:

The same scenario applies when you look up the issue of the Boattail and barrel erosion.

See my next remark below.

quote:

When the base of the bullet does not fully expand and properly seal the bore, some erosion must take place.

This is the major cause of erosion, the bullet base shape has nothing to do with erosion if a quick and effective seal is accomplished.

Gentlemen,

Thank you for your patient explanations to what are obviously very elementary questions. I should have done my own research.

Especially thank you for the references.

Playing the devil's ignoramus has brought me some education, again.

Thank you gentlemen and scholars.

Now I will go check out that Brownell Chapter V ...

AHA!

I suspected at first, Dr. RIP, that you were mimicking Dr. ALF, but then got lost in my incomprehension.

quote:

From government test results (Frankford Arsenal) and those conducted by manufacturers, accuracy will improve and be maintained up to 10,000 rounds using boattail bullets with proper cleaning, while flat-bottom bullet accuracy peaked at around 2,000 rounds and started to diminish by 5,000 rounds.

RIP & Alf,

I would like to hear your opinion on the above. Bear in mind it is just a posted comment on a sight where various writers can post or publish a comment or get quoted. It is not the actual report of Frankford Arsenal with their detailed comments on the subject, but seems to me as a criptic reference to it.

Even if they reported that, I believe the above statement need some thorough scruitiny in the light of the widespread and contradicting experience of serious Benchrest Shooters, who replace their barrels around 1,500 shots according to Daniel Lilja (see comments on his website) . Infact, when we consider that they shoot mostly boatails and they can't achieve the 10,000 mark something is seriously wrong. Accuracy cannot be improved and maintained up to 10,000 shots, unless throat erosion sets in instantantly beyond 10,000 shots instead of being a progressive deteriorating process.
Chris

Chris, Page 25

quote:

I believe the above statement need some thorough scruitiny in the light of the widespread and contradicting experience of serious Benchrest Shooters, who replace their barrels around 1,500 shots according to Daniel Lilja (see comments on his website)

That is not what the article states. Trying to twist the truth again hey? However, you proceed with:

quote:

when we consider that they shoot mostly boatails

More truth twisting and unfounded assumption. The majority of benchrest competition shooting is done out to 300m. By far more flat base bullets are fired than boattails. So could we then assume it is flat base bullets causing all this wear? Of course not, the bullet base has no bearing on wear if everything is designed correctly and within specification.

Why are you so desperate to find any shred of evidence that could prove boattails inferior to flat base bullets?


By the way, why are you still here? Did you not say:

quote:

Consider this the end of this fruitless and futile conversation.

That reminds me about this:

quote:

That is a very convenient but also very transparent ploy to avoid being cornered about the lies about research and opinions of throat erosion caused by boat tail bullets. I asked for references and sources. Where are they?

quote:

Originally posted by John in SC:
AHA!

I suspected at first, Dr. RIP, that you were mimicking Dr. ALF, but then got lost in my incomprehension.

Hi John,
I appreciate your questions and the responses they facilitated. Your questions clarified mine. I am right there with you.

I never paid any attention to the throat erosion issues since I shoot 70 rifles less than 200 shots each per year. I also try to keep barrel heating down and clean after each 20 to 30 shots.

I like to clown around a bit , but I was not intentionally mimicing anyone.

I was having a knee jerk of denial, that was uncalled for.

My fictitious RIPoff Arms, Inc. line of wildcats features a circa 2001 .375 Weatherby Magnum style throat on every one of them, the Big Five. The rifles and cartridges are real, I just need investors to bankroll the company into mass production:

.308/300 Lapua RIPoff
.375/.338 Lapua RIPoff
.423/.338 Lapua RIPoff
.458/.338 Lapua Ripoff
500/470 Mbogo RIPoff

They all have barely subcaliber length parallel-sided freebore run, then a 1.5 degree leade. The freebore diameter is tight, being only .0005" over caliber for .375 and lesser caliber, and .001" over caliber for the bigger bores than .375.

The respective free bore runs and diameters:

.308: run/diam. = .3000"/.3085"
.375: .3700"/.3755"
.423: .4200"/.4240"
.458: .4500"/.4590"
500 (.510): .5000"/.5110"

These generous throats allow enhanced ballistics and ultimate accuracy, but are nowhere near the excessive 1945 Weatherby throat of the original .375 Weatherby that had about 3/4" of parallel-sided freebore run.

I can long seat bullets and still plug the lands and grooves before the bullet base exits the case mouth, using my choice of the longer Monometal bullets.

There is more full diameter shank with the TSX flat base bullet, but the GSC boat tail .375/300gr HV has more than enough full diameter shank for me too.

.375 WBY: use 300 grain bullets
.375 H&H: use 265 or 270 grain bullets

Load them both to the same velocity. The .375/.338 Lapua RIPoff is also intended for .375/300gr bullets at no more than 2800 fps MV, ditto the .375/.404 Saeed, and the .375 RUM, at reasonable pressures, of course. I wonder what pressures Gerard gets in a .375 H&H for 265 grainers at 2900 fps?

The RIPoff Big Five are perfect for the longer monometal bullets, the wave of the future that is cresting now. Why have all that long bullet base sticking down in the case and taking up powder space that could be used more efficiently?

/

Chris,
The Frankford Arsenal claims that a flat base bullet will maintain accuracy to 5000 rounds while a boat tail bullet is good to 10,000 rounds seems counter intuitive.

No one has offered any explanation for this. I sure don't have one.

It would seem that the flat base bullet would protect the throat better than a boat tail bullet ... or does it somehow focus the "cutting torch" gas to worsen effect? Must be too infinitesimal a difference to matter much ... just like the whole gas cutting issue in a longer throat. Seems to be mostly theoretical, not important.

Maybe the boat tail bullets are more inherently accurate for longer barrel life for other reasons than just the amount of their shanks fitting to the bores ahead of the initial gas rush?

Everyone agrees that the short throated overbore cartridges with higher HOE powders scorch away the throats more quickly. That is easily verifiable.

If gas cutting torches occur around the bullet before it seals the bore, this is even more reason to use the slightly longer 300 grainer in the .375 Weatherby that has .3700" long freebore of only .3755" diameter.

Add this to the fact that a 300 grainer will do the same velocity in a .375 Wby as the 270 grainer will do in the .375 H&H.

That is ENOUGH of a good thing.

/

Alf,
Thanks for another field trip to the Museum of Firearms Science.

I seem to recall you posting a picture of that two-banded .30-06 bullet a while back, thank you, no doubt designed by Gerard's grandpappy.

Does a solid copper bullet upset enough to aid in obturation such that a flat base bullet would do any better than a boat tail heel, i.e., is it just that the entire bullet would be axially compressed, thus bulging in diameter, and if any upset occurred it would be equally helpful in both bullets, EXCEPT in that boat tail heel that could never bulge enough to seal the bore in the base portion of the bullet?

Sorry for the runon question.

Does the boat tail shape focus the "cutting torch" gas into a better cutter of the throat.

What are the theories behind Bad-boat-tail vs. Good-boat-tail regarding that two inches of erosion extending forward of the chamber?

You are underscoring some flip flopping going on, supposedly based on Frankford Arsenal observations, or the flopper is bearing false witness.

Does anybody have a handle on this boat tail versus flat base thing with barrel erosion? Why the conflicting statements.

Throughout all the testing around BT and FB bullets and erosion, there is one common factor. I find no reference to the BT bullet being the only change made when erosion increases. Either a hotter load was used, the jacket material was hardened, an under size bullet was used and so on. There are instances of accelerated wear with FB bullets as well. So the conclusion, and this is supported by the extreme accuracy shooters, is that there is no provable difference between the shapes. Logically, and from a mechanical point of view, there can not be a difference that will be statistically significant, as long as the bullet is dimensionally correct and properly designed to contain gas blow by maximally.

A solid copper or brass/bronze bullet does not obturate the bore to the same extent as a jacketed bullet will. Monometal bullets have to be manufactured to the correct dimensions to effect a good seal. If they are not, gas cutting will be accelerated, regardless of the heel shape of the bullet. Numbers that were crunched for us by a couple of guys with way more mettalurgical knowledge than what I could hope to accumulate, put the radial expansion of of a .50 plus caliber bullet of 500gr and up, at around 40 micron. This is for copper, brass/bronze is less. This is in line with my crude (by comparison) axial compression tests on bullets with a hydraulic press. (The test was initially set up for testing of parts we manufactured for the orthopaedic industry.)

Alf, I have seen the picture of the one band Farley bullet. Do you have a picture of the two band bullet available? I cannot find it.

quote:

If gas cutting torches occur around the bullet before it seals the bore, this is even more reason to use the slightly longer 300 grainer

Six of one and half a dozen of the other in this respect RIP. Gas escapes from the moment the case lets the bullet go and before the bullet has left the case mouth. Given that the heavier bullet would be slightly more tardy in getting going but the shorter 270gr bullet has more ground to cover, there is probably not much difference.

/

/

Thank you Alf,
Do you have any idea what the grooved section diameters on the two bullets are? The banded areas would be in the region of .308" (7.820mm).

The top bullet would be the faster of the two. With the bottom one, a section of the ogive, the band behind the crimp groove and the shaft ahead of the boattail would be engraved.

quote:

Originally posted by Gerard:
Throughout all the testing around BT and FB bullets and erosion, there is one common factor. I find no reference to the BT bullet being the only change made when erosion increases. Either a hotter load was used, the jacket material was hardened, an under size bullet was used and so on. There are instances of accelerated wear with FB bullets as well. So the conclusion, and this is supported by the extreme accuracy shooters, is that there is no provable difference between the shapes. Logically, and from a mechanical point of view, there can not be a difference that will be statistically significant, as long as the bullet is dimensionally correct and properly designed to contain gas blow by maximally.

A solid copper or brass/bronze bullet does not obturate the bore to the same extent as a jacketed bullet will. Monometal bullets have to be manufactured to the correct dimensions to effect a good seal. If they are not, gas cutting will be accelerated, regardless of the heel shape of the bullet. Numbers that were crunched for us by a couple of guys with way more mettalurgical knowledge than what I could hope to accumulate, put the radial expansion of of a .50 plus caliber bullet of 500gr and up, at around 40 micron. This is for copper, brass/bronze is less. This is in line with my crude (by comparison) axial compression tests on bullets with a hydraulic press. (The test was initially set up for testing of parts we manufactured for the orthopaedic industry.)

Alf, I have seen the picture of the one band Farley bullet. Do you have a picture of the two band bullet available? I cannot find it.

quote:

If gas cutting torches occur around the bullet before it seals the bore, this is even more reason to use the slightly longer 300 grainer

Six of one and half a dozen of the other in this respect RIP. Gas escapes from the moment the case lets the bullet go and before the bullet has left the case mouth. Given that the heavier bullet would be slightly more tardy in getting going but the shorter 270gr bullet has more ground to cover, there is probably not much difference.

Summary:

THERE IS PROBABLY NOT MUCH DIFFERENCE.

Grudgingly making termite mounds out of mountains, and turning molehills into termite mounds to level the vantage points eh, Gerard?

So it appears now that there is a gas cutting torch around any bullet as soon as the case neck expands enough to release the bullet, before the bullet even starts to move?

Thanks for the 40 micron expansion estimate.

quote:

So it appears now that there is a gas cutting torch around any bullet as soon as the case neck expands enough to release the bullet, before the bullet even starts to move?

This is correct. Erosion is not caused by only one factor. The one you describe above is one of several and can be a substantial contributor or a lessor factor. It depends on the duration of the time from when the case releases around the bullet until the bore is sealed. This can be controlled by the gun builder and the bullet maker.

With under size monometal bullets with ogives that terminate at the shank at barrel groove diameter, a seal is never effected. With the same type of bullet but of the correct diameter, the seal is effected as soon as the ogive is completely engraved and the front of the shaft is fully entered to the end of the freebore and leade. With a drive band bullet, with the ogive terminating at barrel bore diameter, the seal is effected as soon as the front drive band is fully engraved.

quote:

With under size monometal bullets with ogives that terminate at the shank at barrel groove diameter, a seal is never effected ...

If the shank is groove diameter, how can this bullet be "under size"?


I get the concept, but is that statement above some sort of typo? Do we not want the bearing surface to be right at groove diameter?

OK, replace:
"With under size monometal bullets with ogives that terminate at the shank at barrel groove diameter, a seal is never effected ..."

with:

"With under size monometal bullets with ogives that terminate at the shank at what should be barrel groove diameter, a seal is never effected ..."

Yes, the shank should be at barrel groove diameter otherwise bad things happen. Big and heavy monometal bullets will obturate a little if slightly under size but the small, light ones do not. Those are the ones (small, light calibers) that tend to have erosion problems anyway and need all the help they can get.

Clear as mud now!

I have a hunch that Gerard has a big inventory of 265-grain HV and 270-grain FN bullets in .375 caliber, and his stock of 300-grain HV and FN is pretty low.

In fact, I wonder if he has sold any 300 grainers in .375 caliber to anyone besides me, after he begrudgingly made up a small batch of them to stifle my whining for them.

Without doubt we have more 270FN and 265HV on the shelf than the pair of 300gr GSC bullets. We keep a four week inventory of the top 30 sellers on the shelf and a two week inventory of the rest up to about the top 120 sellers. The rest, up to 170, we keep only two boxes of each available.

The point is that we know what the shelf level profile should be and this is determined by the demand, not by what we feel like making. So shelf pressure does not exist in our stock holding, as it would when a manufacturer or dealer makes the wrong call and puts too much of something in stock. Many years of running behind orders have taught us to supply the demand and, historically we know what the demand will be. If a particular bullet has been making up 4.8% of total sales for the last two years, there is no reason why it will not do so for the next four weeks. With the introduction of new bullets to the range, the shelf profile does change but it happens slowly and we find we need to make small adjustments to the shelf profile every quarter.

From a sales point of view, we therefore have no pressure on our philosophy of supplying the right bullet rather than the one in stock. We strongly encourage our dealers to do the same.

Gerard,

So you have stocking dealers in:

Papakura, Auckland, New Zealand: AU and NZ service

Ferrara, Italy: serving Italy, Spain, Portugal

Aberdeenshire, Scotland: serving UK

RSA dealers:
Durban
Uitenhage
Pretoria
Tzaneen
Klerksdorp
Secunda

And the rest of us are left to brave the black hole of RSA shipping and wire transfers of cash ...

Got any .510/450gr HV's on the shelf?

I am placing a test order, again.

My last one went through without a hitch, except for the expense and trouble of a wire transfer.

I do hope it is possible to use a credit card directly this time ...

Ron,

Set your mind at ease. I have enjoyed receipt of 2 non-trivial orders from GSC since the wire thing came about, but now you can pay via credit card which I have also now taken advantage of. No need for a test order at this stage of the game. Just get busy ordering a lifetime supply of whatever interests you.

Dan

quote:

Originally posted by 500grains:
Ron,

Set your mind at ease. I have enjoyed receipt of 2 non-trivial orders from GSC since the wire thing came about, but now you can pay via credit card which I have also now taken advantage of. No need for a test order at this stage of the game. Just get busy ordering a lifetime supply of whatever interests you.

Dan

Great!

It appears variables inhibit compiling the Book of Absolutes, Right Down to the Micron.

Dr. RIP,

I've downsized to just two CF rifles and have a good quality .375 on order. When the GQR is delivered the other two will be sold, one rifle is enough for me and it will get shot plenty. Testing all sorts of loads in the current .375 hopefully will show which will work best for different applications without being wasteful. I've been trying to learn the basics of sound load developement including factors such as barrel life. Having my throat cut does not sound appealing.

I'm a huge fan of RIParms, DOA ammo, the Iron Buffalo, and greatly appreciate your sharing. I really like your cartridges and think the .375 LRO is design excellence.


Enigma,

This is preliminary but may interest you. Ramshot Big Game gave me 2538 fps. from a starting load of 68 grains with a 300 gr. HRN RNSP. Only one shot chrono'd but there is good evidence that 2538 was close to actual and that this is a low pressure load.

But,

after removing a PMP case head at the web, a 300 gr. BBS was seated to AOL ~3.6" which put ~.658" of its length down into the case. The assembly was stood on the bullet meplat and the headless case poured full of Big Game. 71.6 grains is all that would fit. Silly me did not think to tap the case or try to compress the charge. Ramshot claims 75.6 grains is MAX under a 300 gr. Barnes X.

http://www.ramshot.com/powders/loadguide/Load%20Guide%2...%20Web%20Version.pdf

The point: Big Game may be worth consideration by the speed demons who are restricted to the Holland's case capacity.

I'm experimenting with cast bullets now but when the GQR arrives I will crunch powder and numbers and post the results.

Thanks to all.

John,
Thanks. You have a great sense of humor and a very practical approach.

Some more info to add to Gerards explanations of erosion due to barrel/bullet sealing.

This is an email I sent, in which the responce indicates that efficient sealing (by the barrel in this case) is advantageous.

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To: lotharwalther@mindspring.com
Sent: Tuesday, July 25, 2006 8:51 PM
Subject: Polygonal barrels

I am aware that your company manufactures Polygonal barrels

I am to understand that polygonal rifling has certain advantages, one being, increased muzzle velocity.
Would you be able to indicate what typical velocity gains one could expect for the 308win(165-180gn)with 24"polygonal barrel?


REPLY:

We have been making polygon barrels since 1992.

A general rule of polygon is that velocities will be slightly higher. In your stated situation, 50 fps to around 100 fps. This is normally with military ball powder. In the sporting world, where there are various types of powders, this is not necessarily true. There are colder powders and the velocity can be reduced. Other factors will do this also.

The polygon barrel, both the male version and the female version both do the same thing. Seal the barrel against gasses bypassing the bullet. The result of this is the longer barrel life.

If you intention is to buy a polygon to garner a bit more velocity, then you are not using the product correctly.

Sincerely,

Woody Woodall
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