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Thread: Smooth Bore Spin Stabilization? Rifled slugs?

  1. #21
    Boolit Master
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    Quote Originally Posted by Hogtamer View Post
    Those photos are very revealing. Nothing special about the slug but !wow!what a wad. Solid column hard plastic for a straight launch and they obviously believed that centering the wad for a perfect launch is the key to accuracy. The ball being lower than the slug also promotes quick and uniform obturarion. We lowly home loaders can only drool at that.
    That said, I sometimes wonder when experimentation with seating "rifled slugs" on a thick bed of granulated plastic buffer, like Remington factory 20 gauge and .410 rifled slug loads, will begin?

  2. #22
    Boolit Master
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    Notice that the Foster slugs have a solid raised ring around the base to help form a gas seal. This ring is going to prevent smooth air flow along the fins that might otherwise provide some spin. I suspect that if things were reversed and the ring was at the beginning of the fins airflow would be smoother and more effective.

    Military experience with mortar bombs and other fin stabilized projectiles shows that fin stabilization is ineffective above the transonic speed range (+/- 1080-1280 fps) unless the fins project out into the airstream.

  3. #23
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    Quote Originally Posted by Hogtamer View Post
    Those photos are very revealing. Nothing special about the slug but !wow!what a wad. Solid column hard plastic for a straight launch and they obviously believed that centering the wad for a perfect launch is the key to accuracy. The ball being lower than the slug also promotes quick and uniform obturarion. We lowly home loaders can only drool at that.
    This subject comes up alot. This picture of the Federal Slug and wad shows something I have thought about but not talked about very much. keeping the projectile centered in the bore during firing. I consider this to be the primary factor in smooth bore accuracy. I think that ball is there to keep the skirt of the slug centered in the bore as well.

    First: and I want to be clear about this as it is absolute fact. The Ribs on a shotgun slug are NOT there to rotate the slug. Their sole purpose is to keep the slug centered in the bore and collapse if ran thru a choke.

    I asked this question at the Brenneke Booth at SHOT a few years ago and the person with Brenneke as his last name told me they get asked that question a hundred times a day. Since they invented the ribs I would say they are most knowledgeable about this topic.

    Moving on.

    As stated above,,, spinning one turn in 29-129 FEET! accomplishes nothing, and where as it might happen, it doesn't affect accuracy. Lets say the slug is rotating at 1 turn in 50 feet. That's 24 turns per second at 1200 FPS or 1440 RPM. So it might rotate 24 times before it hit a target 400 yards away,,,, or 3 times at 50 yards!. IE: pointless.

    By comparison, a .30 cal bullet shot from a 1:12 twist barrel at 2700 fps is spinning at 162,000 RPM's! Many are twice that.

    That is spin stabilization!

    Now lets look at the other two projectiles. The Slug and the Ball. Assuming both of these projectiles are perfect,,, IE: a Perfect Sphere like a ball bearing, and a perfectly formed Slug, which we'll say was turned on a lathe so there are no casting imperfections.

    Both of these projectiles are launched from a smooth bore and the only influence the barrel has is to accelerate the projectile to Muzzle Velocity.

    I submit that the only things that would affect accuracy would be external forces(wind, atmospheric pressure, temperature) great enough to overcome the inertia of the projectile. Inertia keeps the projectile going in the same direction unless acted on by external forces.

    In space where none of those external forces exist,,, the only thing affecting it's direction would be Gravity of a large entity, and if that were not present the projectile would continue in whatever direction it was headed and theoretically if you could launch many projectiles from the same gun they all should go thru the same hole. Incidentally Rail Guns are Reality and were are talking 15,000 fps! and the shape of the projectile doesn't matter in space. I guess you could compensate for gravity much the same as we do on earth.

    Back on earth, if you eliminate all the external variables, we can narrow our hunt for accuracy down to the shape of the projectile and how consistently we can launch it.

    With respect to the Round Ball, a ball bearing is as good as it gets. My .662 round balls cast from a Lyman mould are decent but they have a prominent Sprue on one side. Once that Sprue starts starts catching air it will affect the flight of the ball, and there is nothing anyone can do about that. However at the distances that ball will be shot. 25-75 yards, and maybe 100 max, it is probably capable of hitting a man sized target, and the results will be devastating.

    Keep in mind that the round ball was the projectile of choice for the first 500 years of firearms. Reason being they were effective!

    Shotgun slugs are a refined version of the round ball. Once again the key to accuracy lies in how consistently they are shaped and launched. Those Federal Wads look like a good way to do it.

    I shot this 3 shot group offhand at 50 yards last week at Front Sight. The rectangle is 3x4" so that is a @2 1/2" group. Don't know if shooting off a rest would have improved the group so I will have to try and get back to you.

    The Ammo was Federal Low Recoil Slugs, and I'd say if you could duplicate that level of performance with your home brewed ammo,,, you were pretty much as good as it gets.

    Randy
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    Last edited by W.R.Buchanan; 05-20-2018 at 02:19 PM.
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  4. #24
    Boolit Master Cap'n Morgan's Avatar
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    I'm sure whatever spin is imparted on a Foster slug (or a Brenneke slug for that matter) is caused by the front of the fins where the airflow and air compression is greatest. The rear of the slug is pretty much travelling in a vacuum.
    Cap'n Morgan

  5. #25
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    Large bore round ball rifles do not require fast rifling. How about 1 turn in 12 feet!

    http://underhammers.blogspot.com/201...ten-magic.html

  6. #26
    Boolit Master Blood Trail's Avatar
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    Quote Originally Posted by W.R.Buchanan View Post
    This subject comes up alot. This picture of the Federal Slug and wad shows something I have thought about but not talked about very much. keeping the projectile centered in the bore during firing. I consider this to be the primary factor in smooth bore accuracy. I think that ball is there to keep the skirt of the slug centered in the bore as well.

    First: and I want to be clear about this as it is absolute fact. The Ribs on a shotgun slug are NOT there to rotate the slug. Their sole purpose is to keep the slug centered in the bore and collapse if ran thru a choke.

    I asked this question at the Brenneke Booth at SHOT a few years ago and the person with Brenneke as his last name told me they get asked that question a hundred times a day. Since they invented the ribs I would say they are most knowledgeable about this topic.

    Moving on.

    As stated above,,, spinning one turn in 29-129 FEET! accomplishes nothing, and where as it might happen, it doesn't affect accuracy. Lets say the slug is rotating at 1 turn in 50 feet. That's 24 turns per second at 1200 FPS or 1440 RPM. So it might rotate 24 times before it hit a target 400 yards away,,,, or 3 times at 50 yards!. IE: pointless.

    By comparison, a .30 cal bullet shot from a 1:12 twist barrel at 2700 fps is spinning at 162,000 RPM's! Many are twice that.

    That is spin stabilization!

    Now lets look at the other two projectiles. The Slug and the Ball. Assuming both of these projectiles are perfect,,, IE: a Perfect Sphere like a ball bearing, and a perfectly formed Slug, which we'll say was turned on a lathe so there are no casting imperfections.

    Both of these projectiles are launched from a smooth bore and the only influence the barrel has is to accelerate the projectile to Muzzle Velocity.

    I submit that the only things that would affect accuracy would be external forces(wind, atmospheric pressure, temperature) great enough to overcome the inertia of the projectile. Inertia keeps the projectile going in the same direction unless acted on by external forces.

    In space where none of those external forces exist,,, the only thing affecting it's direction would be Gravity of a large entity, and if that were not present the projectile would continue in whatever direction it was headed and theoretically if you could launch many projectiles from the same gun they all should go thru the same hole. Incidentally Rail Guns are Reality and were are talking 15,000 fps! and the shape of the projectile doesn't matter in space. I guess you could compensate for gravity much the same as we do on earth.

    Back on earth, if you eliminate all the external variables, we can narrow our hunt for accuracy down to the shape of the projectile and how consistently we can launch it.

    With respect to the Round Ball, a ball bearing is as good as it gets. My .662 round balls cast from a Lyman mould are decent but they have a prominent Sprue on one side. Once that Sprue starts starts catching air it will affect the flight of the ball, and there is nothing anyone can do about that. However at the distances that ball will be shot. 25-75 yards, and maybe 100 max, it is probably capable of hitting a man sized target, and the results will be devastating.

    Keep in mind that the round ball was the projectile of choice for the first 500 years of firearms. Reason being they were effective!

    Shotgun slugs are a refined version of the round ball. Once again the key to accuracy lies in how consistently they are shaped and launched. Those Federal Wads look like a good way to do it.

    I shot this 3 shot group offhand at 50 yards last week at Front Sight. The rectangle is 3x4" so that is a @2 1/2" group. Don't know if shooting off a rest would have improved the group so I will have to try and get back to you.

    The Ammo was Federal Low Recoil Slugs, and I'd say if you could duplicate that level of performance with your home brewed ammo,,, you were pretty much as good as it gets.

    Randy
    Not bad. Reminds me of my 75 yard group with 1 oz Lee key drives.


    Sent from my iPhone using Tapatalk

  7. #27
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    Off a rest, or offhand? They do make big holes! At 75 yards that shows just how effective these slugs can be, and that gun could easily hit at 125-150 yards..

    When you look at the Brown Bess Musket which was the main battle weapon of the British Army for close to 150 years, it is not hard to see that weapon being effective out to 200+ yards in volley fire and probably 150 yards on the unlucky individual recipient of a .75 cal round ball. Those guns were in use well into the 1800's and we have to look at why they were used for so long. Could it be they were really effective on both man and beast?

    Those guns were the ancestors of our shotguns today. Our round balls are not a whole lot better than those shot 250 years ago, but they are just as effective. Our slugs aren't any better than a Minnie Ball, but we can fire more of them before we have to clean the gun so the major advancement was in Smokeless Powder over Black Powder.

    Our ability to change loads quickly is one major advantage we have and lets face it we've got way more firepower. Still avoiding be hit by one of their balls would still be at the top of the list.

    If any of you watched the Stars Series "Black Sails" about the Pirates of the Caribbean there was a scene showing a beach landing of the British Marines. The volume of fire put on that beach was scary and showed in no uncertain terms that they were a formidable force to repel. Also there was a lot of round balls going thru logs and other "cover" which was proving to be not too effective as a barrier.

    My take away was that getting hit by a .75 caliber round ball, anywhere, was almost a death sentence. Whatever it hit was gone.

    This show and my two trips to Front Sight has pretty much convinced me that a shotgun is a far more devastating weapon than any of my rifles in a under 150 yard conflict. My pistols have been relegated to the role of "fighting my way to my Shotgun!."

    Randy
    "It's not how well you do what you know how to do,,,It's how well you do what you DON'T know how to do!"
    www.buchananprecisionmachine.com

  8. #28
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    There's a lot of truth in what you've said here Randy, I'm pretty sure we all agree on the close range effectiveness of a shotgun! In an urban setting or in a home defense scenario the shotgun is a VERY effective combat weapon. Unfortunately it shares the same pitfall of the lever-action rifle, another excellent weapon in the above scenarios: You gotta' keep it fed! As you've pointed out, training is the key to that, not only for the skills of induced muscle memory but also figuring out your rig; How you gonna' carry your ammo, ENOUGH ammo to make the gun a viable weapon- How do you carry it when transitioning from vehicle to ground and vice versa - How to transition to pistol when needed? These questions, and others, are only sorted out by training under pressure. Probably the single biggest question for most guys is how to carry enough ammo. Let's face it, the size/weight ratio of 12 gauge to 5.56 ammo is about 1:3 and the carbine ammo comes in neat, handy little magazines, shotgun ammo doesn't. Still, with good training, we can neutralize some of the negatives.
    "We'll kill them ALL!"

    Optimus Prime at the Battle of Chicago

  9. #29
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    Centershot: There are several ways to carry the ammo.

    My Shotgun Belt which is a Lowes tool belt with two Competition Shell carriers (sold by Dillon) and a Dump bag is my current setup. I can hang a third one if needed but you can only have so much as it eventually will pull your pants down.

    What I was doing during the massive fire drills was loading from the shell carriers, with a full box in the dump bag to replenish the shell carriers when time permitted. When I didn't have time to reload the shell carriers, I simply grabbed individual shells from the dump bag and port loaded using the technique they showed us for left handed shooters. It is the same 4 finger hold on the shell trapping the shell between your index and pinky finger and using the other two to push the shell into the port, just reversed for lefty's. see pic below.

    The gun never comes off the shoulder for these operations. You load from underneath the gun, and You tilt the gun hard to the right to give yourself more room to hit the port with your left hand.

    This all takes practice, and nobody was born knowing how to do it. There are also many variations of these techniques taught by different schools. I saw one guy who was spitting a shell into the port with his mouth, and he only fed the gun over the top because he thought it was faster.

    You also need a shell carrier on the gun for Home Defense so you always have ammo on the gun. Don't get the plastic ones! Get a "Velcro" one ! as when it is empty all you do is rip it off and slap another one on. also there is no mods to your gun if you get the right Velcro one that just has a piece of Velcro tape stuck on the receiver.

    I got mine from Browncoat Tactical and they are like $15 each. See pics.

    This stuff is not that complicated, however if you don't know these techniques exist it can be pretty daunting to figure them out for yourself.

    here's pics.

    Randy
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    "It's not how well you do what you know how to do,,,It's how well you do what you DON'T know how to do!"
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  10. #30
    Boolit Master
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    Randy, that belt is an ingenious rig, just goes to show what a little thought and imagination can do! When I'm out "shopping" I'm always looking for stuff that can be "other-purposed"!
    "We'll kill them ALL!"

    Optimus Prime at the Battle of Chicago

  11. #31
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    Yeah,,, I think it was $12.95 and included a tool pouch which I think is in one of the garages never used.

    The majority of my Range Bags are Lowes, Home Depot or HF Tool bags. I can't justify paying $100 for something I can make work, and will do the job just fine for $10-15. My first Lowes Tool Bag for my G35 was from 2006 and it is still in use, and in fact it went with me to FS last week.

    I also like the LAPG Bail Out Bags which are usually $19.95 on sale. I use them for Range Bags and Pistol Carriers and Ammo Carriers. LAPG has some of the best bags made and the prices are ridiculous low. 3 day Backpacks from $29.95 and they are better made than Maxpedition or any of the high end makers which are 5x the price. I just got an email from London Bridge with all of their 3 day or School packs on sale,,, For $99.95! They are not even half as nice as the LAPG bags which are 1/3 the price. I don't care that they are "Made in Vietnam," as I consider that to be better than "Made in China."

    Anyway that's how I do it. YMMV fits here.

    Randy
    "It's not how well you do what you know how to do,,,It's how well you do what you DON'T know how to do!"
    www.buchananprecisionmachine.com

  12. #32
    Quote Originally Posted by W.R.Buchanan View Post
    Off a rest, or offhand? They do make big holes! At 75 yards that shows just how effective these slugs can be, and that gun could easily hit at 125-150 yards..

    When you look at the Brown Bess Musket which was the main battle weapon of the British Army for close to 150 years, it is not hard to see that weapon being effective out to 200+ yards in volley fire and probably 150 yards on the unlucky individual recipient of a .75 cal round ball. Those guns were in use well into the 1800's and we have to look at why they were used for so long. Could it be they were really effective on both man and beast?
    They were used because in conjunction with rigorously indoctrinated mechanical drill of the kind that remains fossilised on the paradeground, their speed of loading made their abysmal accuracy preferable, for ordinary infantrymen, to the advantages of the rifle. Frontiersmen and Indians probably used a tight-patched ball, but those of line infantrymen would be smaller, to cope with heavy fouling. They also didn't get to pick and choose their gun, at a time when even quality sporting guns weren't as well bored as they would become once the customer got to look through the barrels, and military issue ones were often very badly bored.

    Firing a volley at a battalion of well-drilled men, discouraged by flogging of firing-squad from considering the good of their health, would kill few people. It would also be a disastrous invitation to march forward in good order, and fire at twenty yards or so, a volley about as dangerous as any firearm ever made. There was a famous incident at the battle of Fontenoy, when British officers invited the French to take the first shot. I don't know the distance, but most likely it was an attempt to see if they could be suckered. The reason for volleys was also good at that time. It minimised the time in which men would be firing blindly into the smoke.

    I have the memoirs of Napoleon's chief of military surgery, Baron Larrey. As in the American Civil War, surgical facilities were sometimes overwhelmed by volume of cases in the big battles, but were far more advanced, when they had the chance, than the traditional rum and hacksaw image. The round ball was indeed very effective, if you could just get it to hit someone. But it didn't produce devitalised tissue which had to be removed, to nearly the extent a modern bullet does, and while it would break bones, it didn't shatter them in the way the Miniť or early breech-loader bullets did.

    I don't know if it was Lincoln who originated the term "twenty dollar words", a concept which, as a lawyer, must surely have made sense to him. But the word "tactical" seems to fetch a lot more than that nowadays.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check