Slug accuracy - Rifled Foster Slugs vs Sabots and other rifled barrel slugs
I heard a fellow say at the gun show that foster slugs in a smooth barrel can actually be more accurate than rifled slugs.
Irrespective of that claim, I'd sure like to know before sinking funds into a rifled barrel shotgun how the accuracy usually looks of each.
Some have claimed MOA or 1.5 MOA from their rifled barrels. That's far from what I'd need out of a slug gun. All I would need is combat accuracy, say 4 MOA, since I'd be using open sites at not extremely long range.
So how does your accuracy look when firing foster slugs, say Brennekes, out of a smooth barrel with rifle sites?
Trust is earned, not... GIVEN away. - Worf
Shooting the standard Foster type slugs in my Rem 870, cutdown 20 inch straight cylinder bore barrel - I keep them inside two inches at 25 yards. I haven't tried them longer than that. I have some fairly flimsy sights that clamp onto the ventrib. Adequate, but not truly combat grade.
SHOTGUNS AND SLUGS are a short-range combination. A look at the ballistics tables in any ammunition catalog will tell you so. Most of them give numbers out to only 125 yards, and for most slugs, even that is stretching it.
But the situation is changing and changing rapidly. The effective range of shotgun slugs is growing almost by the day. A field that was a ballistic backwater until a decade ago is suddenly one of the most interesting areas of research for a ballistician. Ammunition makers are racing to develop slugs for a high-tech age.
The reason? Demand, motivated by regulation. More and more jurisdictions are mandating shotgun-only deer seasons.
"Half of all the deer shot every year are taken with shotguns," says Remington research engineer Vince Scarlata, "and of those, I would say 90 percent are shot with slugs. That is a huge market. And, with the developments we are seeing, shotgun-slug research has become an exciting field."
All the research in the world, however cannot repeal the laws of physics, and it is those immutable laws that have, for more than a century, made shotgun slugs a 100-yard proposition.
Shotguns as we know them descended directly from muskets-smoothbores that fired both charges of pellets and single-- round lead balls. These single projectiles, popularly called "pumpkin balls," worked well enough out to about 50 yards. With the arrival of choke-boring, however, even that minimal effectiveness was reduced. With balls made small enough to fit through even the tightest choke, accuracy fell off alarmingly.
In the 1930s, a shotgunner named Karl M. Foster developed the slug that now bears his name. Cup shaped, with a hollow skirt that would expand to fit the bore, the Foster remained one of the two dominant slug designs for half a century. Winchester began loading them in 1936 and still does. The other design was the European Brenneke, which employed a lead cylinder with a fiber wad attached to the base. Both the Foster and the Brenneke have lead vanes which impart a slight spin for stability, but do little to enhance accuracy.
The Foster and the Brenneke are effective out to about 100 yards. Beyond that, you run into several problems. The biggest is that you lose accuracy. Right behind that is loss of killing power. And, as the slug sheds velocity, it begins to plunge like a stone. In the search for a slug that is effective out to the unheard of distance of 200 yards, these are still the three obstacles that must be overcome.
Every engineer in the field agrees that a gun-and-slug combination that is effective beyond 150 yards will have a fully rifled barrel and will shoot sabot slugs. Smoothbores and Foster slugs will never cut it. Let's look at each of these three obstacles individually from a gun and projectile point of view.
For deer, you need to be able to keep all your shots in a 6-inch circle at 200 yards.
The major challenge in this area lies with the ammunition, not with the gun. It is a simple matter to put a rifled barrel on most standard shotguns and attach a scope that allows precision aiming. Put on a 2.5X or 4X scope and you have the accuracy you need.
A sabot slug then gives you a combination of rotation for stability and a decent ballistic coefficient. Sabots have been around for a couple of centuries. They were first used in muskets. The word is French for the wooden shoes that were common in the 18th century, and were so named because the first sabots came in two parts, each resembling a shoe. The musketeer enclosed his bullet inside the two halves, and pushed the whole thing down the barrel.
Today's shotgun sabots are made of synthetic material that hugs the rifling, imparting a high rate of spin without exceeding the standard shotgun breech-- pressure limit. When it exits the muzzle, the sabot falls away, leaving the slug rotating like a rifle bullet. Using sabots, shotguns can be made to fire slugs that closely resemble rifle bullets from a .45-70 or similar cartridge. They can be jacketed or have hollow points. Most important, they have a much higher ballistic coefficient than standard slugs.
Typically, the Foster slug has a coeffident of around .07-so abysmal that most ballistics charts do not give the velocity and trajectory figures for it (.09 is as low as most of them go). The new Remington solid-copper slug has a coefficient of .211, while their newest bonded slug has a coefficient of around .300. Suddenly, we have a projectile capable of both long-range accuracy and velocity retention.
With the old slugs, velocity was shed so quickly after 100 yards that penetration suffered. With sabot slugs, most of which weigh about an ounce, the penetration and killing power will be there at 200 yards provided you actually hit the target. Expansion is generally not a consideration as it is with rifle bullets. Even the smaller sabot slugs have such a wide diameter (typically .50 caliber) that they do not depend on expansion to provide punch, although the newer sabot slugs like the Winchester Partition Gold and the bonded Remington do provide expansion capability if there is sufficient retained velocity.
Remington's solid-copper slug has a muzzle velocity of 1,550 fps and a very respectable energy of 2,334 ft.-lbs. At 100 yards, the energy has dropped to 1,600 ft.-- lbs., and at 200, with velocity down to 1,096 fps, energy is only 1,167 ft.-lbs-just enough killing power for a deer-sized animal.
The real problem as velocity drops is the increasingly steep trajectory of the bullet. Between 175 yards and 200 yards, a standard slug may drop 10 inches! This being the case, a range miscalculation of as little as 25 yards can cause a miss even if everything else is right on.
Fortunately, a great deal of deer hunting today is done from stands. A hunter can use a laser rangefinder to pinpoint the distance to visible objects. When a deer appears, he knows almost to the foot how far he is shooting. Since sabots date from the era of muskets, why not use range stakes, which were also employed by Wellington's infantry?
Looking at these three areas, it becomes obvious that the best way to extend the range of a slug is to increase the muzzle velocity. With projectiles that better retain velocity, you get more downrange energy and a flatter trajectory. Unfortunately, the governing factor here is pressure. Shotguns are built to withstand maximum-breech pressures of 11,500 psi, whereas a deer cartridge in the .30-06 class will take 50,000 psi.
The 3-inch 12 gauge works at 14,000 psi. While it has slightly superior ballistics, the longer shell does not offer a great range advantage, nor much potential for improvement.
"The extra room in the case means you need a bigger wad," says Scarlata. "It does not mean you can stuff in a great deal more powder."
Engineers working to develop better slug guns must do so within those pressure limitations. Otherwise, what they create may not be a shotgun at all.
"There is no real definition of a shotgun used by the game departments," says Scarlata, "But a good rule of thumb is that if a firearm uses a cartridge that can be fired from a standard shotgun, then it is a shotgun.
"When we first introduced the sabot slug, a half-dozen states threatened to disallow it. Their objections were withdrawn when we showed that the slug started to tumble at about 225 yards, which limited the range severely. Our new slugs will not start to tumble until about 275 yards, but that is still close by rifle standards."
Ammunition companies always have to keep that fact in mind: Shotguns are mandated because they are short-range weapons. Develop a combination that stretches the range too far and you run the risk of having the gun outlawed.
Given the limitations on the ammunition, 200 yards would seem to be the extreme we should look for in a slug/gun combination, and then only under conditions where ranges can be measured accurately. But consider: Just 10 years ago, 200 yards looked like a pipe dream. Now we are there, and new developments are coming thick and fast.
Copyright Sports Afield, Inc. Jun 2002
Provided by ProQuest Information and Learning Company. All rights Reserved
Don't know crap 'bout shotguns. Can't help ya man, sorry
There’s always an Arquillian Battle Cruiser, or a Corillian Death Ray, or an intergalactic plague that is about to wipe out all life on this miserable little planet, and the only way these people can get on with their happy lives is that they DO NOT KNOW ABOUT IT!
Well OneInchGroup, got any insight on the best I could expect from each? I'm talking standard production shotguns and barrels, nothing fancy custom or such.
I did only slightly better with my rifle barreled 870 and sabot slugs with open sites than I did with rifled slugs and a bead site on a cylinder barrel.
:smash: Conventional wisdom is Foster slugs or other rifled slugs for Smoothbore out to 50-60 yards, where velocity starts a rapid drop and most slugs start to tumble. Sabots for smoothbore from 60-100 yards, where the extra speed and longer projectile length tend to retain more accuracy. Ideally, ranges beyond 50 yards ought to be considered the realm of the rifled barrel gun firing saboted slugs, as they can be acceptably accurate and maintain killshot energy levels out to 200 yards, if deer are the targets.
The current greatest controversy is not whether it should be sabots or other slugs over 75 yards, but which of the sabot types is the best. What we seem to be seeing in general is that what are being called "impact discarding" sabots look to be the ultimate long range recipe. "Muzzle discarding" sabots, whether they "flower petal" and fall away, as some that are basically a shot-cup style plastic wad with splits, or a fully segmented sabot that drops away as the round clears the muzzle, all tend to produce "flyers" from time to time. What photography there is seems to be showing an uneven discard, with one segment or one section opening first, and dragging the projectile away from the "sticky" side. Seen a few where 4 of five shots at 100 yards were inside an inch, and the fifth missed by 2 or 3 FEET. Sticky wads pulling right, left, high, low, whatever. Sabots that stay connected until the target impact seem to act much more like rifle bullets, airflow over the attached plastic sabot stabilizing the trajectory. Those don't have the surprise course changes that seem to plague "normal" sabots and ordinary slugs when you get out to 100 yard range. Generally I don't offer up a single brand as the best, since you don't want to be telling your ASSA competitor members what ammo the judges are favoring. Some sort of objectivity has to be maintained.(We'll fess up on PM, but not if you're in one of our contests.)
My mossy with the ghostring usually gives me about 5 inch groups at approx 100yds. Thats if i do my best. Have gotten the occasional 3 incher, but just as many 10 inch groups. It'll kill deer and has worked wonders on "varmints", but definitely NOT a superaccurate setup.