Long Range Sabot Rounds

[RustyBattleship]

Originally Posted by eocoolj

Also, what are bourlettes?

A bourlette is a notched "groove" impressed into the projectile. The main purpose is to provide a groove for the "lip" of crimped cartridge cases to seat into.

This provides sealing against water and prevention of the bullet falling out (from recoil of previous shots rather than dropping on the ground).

[RustyBattleship]

[quote=tlturbo;424782] Rusty - is you Mod 97 US ord marked and original? I lost one in a house fire in 2000 and I'm looking for a replacement if you want to sell it. [quote]

Not at this time. We keep it as our "house gun" as well as one of my magnum revolvers. Besides, it's a "civilian" model that I bought from my boss at work when he sold his late father's collection.

Besides, when I kick the bucket only the family heirlooms will stay and I've arranged with a friend in Carlsbad that holds an FFL to help the family sell the others.

[RAL's_pal?]

Originally Posted by RustyBattleship

I have an appointment with an orthopedist next week. One finger is still swollen (since Father's day) and the other fingers are getting numb. Probably tore a tendon loose.

Gee, I missed this latest stumble, fumble, fall of yours.

Are you sure it was at a BBQ and not some other cause?

[RustyBattleship]

Originally Posted by RAL's_pal?

Gee, I missed this latest stumble, fumble, fall of yours.

Are you sure it was at a BBQ and not some other cause?

Absolutely sure. I never forget Bar-B-Ques where I relocate any one of my joints.

[dave lukins]

Originally Posted by RustyBattleship

Ummm, what tank are you talking about?

.

Centurion 105mm. We had .50 ranging. .30 machine gun next to it and a Commanders .30 on the cupola

[Shipwreck]

Originally Posted by dave lukins

The .50 on Tanks was only used for ranging. A solanoid automatically fired 3 rounds at the target. A good gunner can rapidly move up the sight scale giving the Commander his range to the target..Alas the Laser Range finder has taken that away.

Originally Posted by RustyBattleship

Ummm, what tank are you talking about?

Originally Posted by dave lukins

Centurion 105mm. We had .50 ranging. .30 machine gun next to it and a Commanders .30 on the cupola

Chieftain also, until the RMG was replaced by the TLS in the early 1970s.

[tlturbo]

I've never seen the band itself called a cannalure. We have always called it a driving band (because it and the rifling drive the projectile around) but I guess I've never really seen it named that. It's always called a rotating band like Rusty said. But a cannalure is a groove or group of grooves. On a small arms bullet (if necessary) it is a ring of little notches located where the top of the case would be on a loaded round and allows a slight crimp in the neck lip of the case to be pressed into the bullet to help hold it in the case. In a large projectile, like a 16", it is the several groves that go around the rotating band to allow copper that is displaced rearward by the rifling to accumulate. Like stated before, the bourrelet isn't a groove but an oversized portion of the projectile that rides on the top of the lands.

Here is an excerpt from Slovers site.

3D3. The bourrelet

The forward bearing surface of a projectile is machined to a fine finish to reduce friction and minimize the wear of the gun. In small projectiles the entire body forward of the rotating band may be finished to bourrelet diameter. On large-caliber projectiles additional bourrelets, abaft and forward of the rotating band, are added to provide better support, especially during ejection from the muzzle. A certain clearance must be provided between the bourrelet and the lands (the raised portions of the rifling). Standard United States Navy practice requires a specified bourrelet diameter 0.015 to 0.023 inch (in different-caliber projectiles) smaller than the diameter of the bore. To this margin is added a manufacturing tolerance of minus 0.005 to 0.007 inch, so that total clearance limits vary from 0.015 to 0.030 inch. Unnecessary clearance adversely affects accuracy and fuze performance and may mar the rifling by excessive wobble.

3D4. Rotating band

The three primary functions of the rotating band are to seal the bore, to position and center the rear end of the projectile, and to impart rotation to the projectile. Its secondary function is to hold the projectile in its proper position in the gun after loading and ramming, and to ensure that it will not slip back when the gun is elevated. The band has considerable effect on muzzle velocity, range, accuracy, and the life of the gun.

Rotating bands are usually made of fine copper; in major-caliber projectiles a small percentage of nickel is added to provide greater strength. Some projectiles of recent design have been banded with gilding metal (90 percent copper, 10 percent zinc), which increases strength and reduces the amount of copper deposited in the bore of the gun.

To reduce dependency on copper for this use (copper is increasing in military importance while it becomes scarcer and more expensive) rotating bands of sintered iron are under development.

United States Navy projectiles generally have rotating bands about one-third caliber in width. Foreign services sometimes use narrow multiple bands on major-caliber projectiles. The rough band is assembled (after heating it, in 8-inch and larger calibers) by slipping it over the rear of the projectile and pressing it into a score cut into the body of the projectile. This scoring usually includes a dovetail on each edge to assure that the band will not be thrown off by centrifugal force. Either waved ridges, longitudinal nicks, or knurling are provided on the bottom of the score to ensure against band slippage during rotary acceleration.

The forward edge of the band is slightly conical, to facilitate engagement with the origin of rifling. The cone, during loading, wedges into a seat at the origin of the rifling (except in fixed ammunition) and holds the projectile in place during loading and elevating. The central portion of the band is cylindrical and of a slightly greater diameter than that of the bore plus the depth of the rifling. This portion is sometimes divided by circumferential grooves, called cannelures, which provide space into which displaced copper may be wiped. In the after part of the band separate-loading projectiles have a raised lip followed by an especially deep cannelure. The lip serves to ensure a good gas check and also to prevent overramming in a badly worn or eroded gun.

The purpose of the cannelures is to minimize the formation of a fringe or skirt from the excess metal which is wiped rearward. Such a fringe is likely to flare outward, at the muzzle of the gun, due to the effects of the gases and of centrifugal force, and cause loss of range and accuracy. Bands on which the lip is well forward of the end of the band and is undercut with a deep cannelure are known as nonfringing.

[Gun Grape]

Originally Posted by RustyBattleship

A bourlette is a notched "groove" impressed into the projectile. The main purpose is to provide a groove for the "lip" of crimped cartridge cases to seat into.

This provides sealing against water and prevention of the bullet falling out (from recoil of previous shots rather than dropping on the ground).
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That all copper band near the base of the projectile is properly known by two different names. One is the cannalure band and the other is the rotating band. Cannalure is the accepted technical name though Rotating is what it is actually used for as well as a gas-check.

Rusty, I think you may be using small arms terminology which differs from artillery terms. The cut off point of small arms being 40mm. Anything over is artillery, be it land or naval.

TlTurbos definitions are close to official DoD with a few additions.
[Blockhouse mode on]

The bourrelet is an accurately machined surface that is slightly larger than the body and located immediately to the rear of the ogive.

The purpose of the bourrelet is to center the forward part of the projectile in the tube. It bears on the lands of the tube to provide forward support of the round during firing.

The rotating band does not engage the rifling of the tube but instead engages the start of the rifling in the forcing cone of the tube.[Blockhouse mode off]

I have never seen or heard of a bourrelet behind the rotating band. Some rounds have bands rearward of the rotating band but those are Obturating bands

[tlturbo]

AH HA I knew I had seen it called "Driving Band" somewhere.

These descriptions are from the Nav Weapons website:

Driving Band - A raised ring of soft metal encircling a projectile. Also known as "rotating band." These are made of copper, brass or soft steel. USN driving bands on large caliber projectiles consisted of 97.5% copper and 2.5% nickel. There may be more than one band on each projectile. The bands engage the rifling in the gun barrel, causing the projectile to spin as it travels through the barrel. They also provide a tight seal so that the propellant gases do not escape past the projectile as it travels down the barrel. An "augmented driving band" or "augmented rotating band" is a slightly thicker strip of metal used when the rifling in the gun barrel has been worn down. See "Rifling" above.

Bourrelet - Finely machined band or ring of metal just behind the ogive of a projectile, designed to support the front portion of the projectile by riding the lands as the projectile travels through the bore of a gun. Only the bourrelet and the driving bands of a projectile actually touch the rifling. Some projectiles have a second bourrelet located between the base of the projectile and the driving bands. This second bourrelet acts to reduce the tip-off angle by keeping the projectile body centered in the gun barrel after the forward bourrelet has exited the muzzle.

Cannelure - Means a ring-like groove or a groove encircling a cylinder. These have the following uses in ammunition and weapons:
1) On projectiles used in fixed ammunition: The groove provides a means of securely crimping the cartridge case to the projectile.
2) On armor-piercing bullets: The groove is used to lock the jacket of an armor-piercing bullet to the core.
3) In the rotating band of a projectile: The groove lessens the resistance from the rifling as the projectile travels down the gun barrel.
4) Around the base of a cartridge case: The groove is where the extractor takes hold to eject the spent case.
5) In the construction of British large-caliber, wire-wound weapons: Cannelured rings were used to prevent "steel choke" problems.

Now that that is cleared up HA HA