I took my mossberg 835 out to try some new sabot slugs and I just can't understand my results HELP

using winchester 12ga 2 3/4 1 oz 1350fps i am 1" high at 50yds
i then switched to some winchester platinum tip hollow point sabots 400gr at 1700 fps and at 100yds they go over the top of the target. i made a mistake of switching to 100yds with just the new slugs but i can't believe they shoot that much higher.. is it possible for the bullets arc to move out that far? after doing some research i understand that the 400gr sabots are somewhat acurate at 200yds???

 

According to the last book/magazine article I read on this, the slug or bullet is not gaining altitude. It is being fired at an upward angle.

After the projectile leaves the barrel, there is no more force acting on it, so unlike a rocket, it can't propel itself.

This seems correct to me, but the question of aerodynamic forces bothers me. But I don't see how a projectile like that could have an aerodynamic shape that would allow it to gain altitude. Especially if it's spinning. It ain't a wing.

Anyway, can you bore sight your shotgun and see where the zero is? If you are zero'd at 200 yards, everything is going to be high at 50 and 100.

 

You are always aiming higher then where you hit. your original shot should have dropped about 4 inches from where you where pointing the gun. your second type should drop about a foot from where you aim. This is based on the velocity and time it takes to reach the target. Now, if you usally use the first type of shot and have your gun sighted in for it then you switch, there might be something to do with shape of the round that has much lower drag so it is actually taking less time to get to the target then the first round. This may be how they are able to hold accuracy to 200 yds. If the first were not hollow points then this might be a reason too. I would think that the hollow point might act kinda like a dimple in a golf ball and lower the drag by breaking up the surface layer. another thing that might acount for this is a more ballanced round and therefore more effect from the spinning.

 

Hey!

Well, a 1 oz. slug weighs 437.5 gr. And it's moving 1350 fps. 1" high at 50 yds.

Your 400 gr. slug (a tad more than 7/8 oz.) is moving at 1700 fps. Over the target at 100 yds.

The physics is not too complicated to begin: If a gun barrel is held perfectly level then the projectile will drop 32 feet in the first second of it's travel. (And will drop faster and faster at an increasing rate of 32' per second, per second. Thus: 32' down in the first second. By 2 sec. of travel it is down 96'. By 3 sec. it has fallen 192 feet!) A modern high-velocity "flat-shooting" rifle cartridge will travel a very long way in that first second. (For example, a Ruger .204 doing an even 4000 fps will travel almost exactly 3/4 of a mile in that first second.) So, at 3/4 of a mile that slug has dropped 32'. If you wanted to hit where you aimed at that distance, you'd elevate the muzzle way up, so you were actually aiming the barrel at a point 32' above your target at 3/4 of a mile out.

Your first slug is travelling at 1350 fps. So it would go about 1/4 mile in a second. Aim for the target you were hitting with your Ruger .204 and that slug won't get there for 3 seconds. You will have to hold 192 feet over the target! So there's your "rainbow effect."

Of course you aren't shooting at anything that far out, but the physics still works albeit on a smaller scale. You still have to aim the gun barrel up to hit what you're aiming at. The slower the round is going the more UP you need.

To compress the scale for 50 & 100 yard shooting and get some real numbers, your 1 oz. load will get to the 50 yard target in 0.111 seconds, and to the 100 yd. target in about 0.222 sec. Now some formulas I haven't used in a while come into play and I might miss something, but I'll try to make sense with this:

At 50 yds. your 1350 fps load will have dropped 2-3/8". At 100 yds. it will have dropped 9-7/16".

Now we switch to your 1700 fps load.
It will get to the 50 yd. target in 0.088 sec. and to the 100 yd. one in 0.176 sec. At 50 yds. it will fall 1-1/2". At 100 yds. it will have dropped 5-15/16".

All things being equal, you probably shouldn't have blown over the top of the 100 yd. target, if you were one inch high at 50 yds. The other thing to consider is that few rifles (and probably no shotguns) can be counted on to perform exactly "rationally" with varying loads from different manufacturers. Sighting in with a new load is basically starting from scratch. If you want to try it out at 100 yds. you'll at least need a large target, or a big sheet of paper to back it so you can tell for sure where your new rounds are grouping.

For clarity, no, a bullet can't rise above the line of inclination at which it was fired. But you are actually pointing the bore up above the target so the slug will lob up, through the apex of an arc, and then back down to the target at the range at which you're aiming to be zeroed. When you do get the point of impact of that load figured out, I'd set your sights to the point of impact at maybe 75 yds. or so. That way you know that the bullet will only rise about 2" before it gets to 75 yds. and will only fall a few inches between there and 125 yds. or so. That way you can aim dead on for every shot between point blank and 125 yds.-ish and know that the slug will always hit within a target zone that's the size of a deer's vitals area. There are programs and guides that can help you determine very accurately what those exact numbers are. Usually its referred to as "maximum point blank range."

Good luck!

-Sam

 

You gotta remember you are asking the question on a Ford truck site, not a ballistics forum. Thus the conjecture.

Here's why:

Point of impact has to do with the velocity of the projectile, the time it spends in the barrel, and the motion of the gun under recoil. The barrel vibrates and the gun starts moving as soon as the gun is fired and the bullet starts accelerating down the barrel. The bullet leaves the gun at a different point in time, depending upon its velocity. The barrel is pointed somewhat UPWARD, in relation to the ground, when the bullet exits the barrel. It has to be this way, since if the gun was fired with the barrel level to the ground the shot would always hit under the target. Bullets respond to gravity like everything else. In my .35 Remington lever action, for example, the heavier, slower bullets hit HIGHER on target than the light, fast ones, because of the longer time of bore travel, and due to the fact that they exit the muzzle at a higher arc-recoil has had more time to drive the gun upward before the bullet exits, and it exits at a higher angle than a lighter, faster bullet. This is assuming the gun is zeroed with one type of ammo (light fast) and is later fired with slower, heavier bullets. The opposite would occur if the gun was zeroed with heavy, slower bullets and then lighter ones were fired-the lighter bullets would hit low.

No, I haven't repealed the laws of physics. Compared to the lighter faster bullet, slower bullets always drop more over the same distance. But this fails to consider the angle of exit when the bullet leaves the muzzle. Widely different bullet weights and velocities will hit at widely different points of impact in the same gun, and the direction of impact is often oppposite of what you'd intuitively expect. Sometimes it is gun specific, and it can vary.

Just remember this: when you zero your gun for one bullet weight and velocity, it may not hit anywhere close when you switch ammo.

ALWAYS hunt with the same ammunition that you zeroed the shotgun/rifle with. Another brand advertised with the same bullet weight and speed may hit in the same place, and then again it may not.

Shotguns, with their relatively thin walled barrels and widely varying slug weights and velocities are particularly susceptible to this. The thin walled tubes are very vibration prone and heat up quickly with sustained shooting. Divergent points of impact result. That's just the way it is, and by always using the same type/speed of ammunition it is easily dealt with.

Incidentally, hollow points are frequently used to shift the center of balance of a bullet, usually to the rear. This often results in more stability for some projectiles, like rifle match bullets, but it has less to do with aerodynamics and more to do with bullet balance. The hollow points in rifle match bullets are so small that they really do not affect the aerodynamics. The dimpled bullet thing is often mentioned because they are seen on golf *****, but no bullets are manufactured with little dimples on them. In most instances, hollowpoints are present to improve the expansion (mushrooming) characteristics of fairly low velocity projectiles, like pistol bullets, and .22 long rifle bullets. Shotgun slugs are so large in diameter that the hollow point is usually not needed. They make a big enough hole as is, but some sabot type shotgun slugs use them to good effect, firing a subcaliber projectile in a larger shotgun bore.

In ammunition, there are so many different types that there is something for every taste and need.

 

Thanks for the help. I realize that you are creating the arc by the angle of the gun but still find it hard to believe that it made this much of a difference. I bought some of the origional slugs that i'm going to use this week (hopefully) and when I have time I'm going back to the range with lots of several types to work this out. It just never fails that Monday is opening day and today was the first chance I had to go to the range.
Mike

 

psu1xj,
I still have one question that you may have explained, but I missed!

Is there a rate of drop for a bullet of a given weight over a given distance?
How far above a live target do I allow for per given ft in distance. IE( 6"drop per 140')
drop at 200" drop at 300"?

 

psu1xj, I'm an old pistol silhouette shooter, you are on the target with your statements, hats off to you, thanks. Many people will pass BS real thick if they don't know, you don't. Others who say this is a truck forum not guns and amo, respect the added knowedge everyone, can't we just get along.
thanks, Carl.........o&o>.........

 

68 351 bronc. In actually there would be, but very difficult to calculated and would have to be almost calculated for every brand and assume the guns are all the same. It has to do with aerodynamics of the round as well as mussel velocity. Thoreticaly weight does not play a role in this other than that a heavier round may be more acurate at a wider range of distances becuase it can maintain more momentum with a given drag force acting on in the a lighter round with the same drag.

That being said you can get a scope for most guns with tick marks on the lens. You can then gage where you need to aim in the site to hit a target at a given distance. Although I don't shoot more than for fun I used to do archery and the theory is the same, just with a bow you have pins that you set for diffrent distances.

I have a feeling that this might turn into a thread for engineers to debat the aerodynamics of amuntion.

 

psu1xj is right on the money! Now factor in a variable headwind or crosswind and you can see it's just short of a miracle we hit anything we're aiming at!
Without these variables,hunting and target shooting would lose a lot of the fun that each of our individual talents and skills bring to the sport.
FYI:An interesting thing for the slug hunter.Using a heavy shot load,open the crimp and pour in hot candle wax or parafin.Recrimp and try it on a tough target such as a thick board,etc. At a short or medium range this thing will bring down an elephant! Just a neat remedy for when your in camp and your out of slugs.
I've even tried this with a scatter load and was amazed at what it would at short range!

 

Well, the rate of drop (downward acceleration) is always 32 feet per second, per second of bullet flight time. Usually this is somewhat altered by wind resistance and other variables, but that's the law. As I probably showed in my first post, this is not easy to translate quickly into practical data for a specific cardridge.

Good news is, there are whole tables of this stuff published just to answer these questions. I used to have a real old copy of a /Gun Digest/ annual buyers' guide (or something like that) that I kept around just because the last 200 pages (so it seemed) were covered with spreadsheets showing drop and energy changes at lots of different ranges, for all kinds of cartridges and many bullet weights in each cartridge. I can't find that book right now but my /Hornady Handbook of Cartridge Reloading/ has a decent version of that in the back, though it doesn't cover shotgun slug-type loads.

I also have a CD from Sierra Bullets that will do all kinds of external ballistics calculations like that, but I've never gotten around to playing with it.

I'd hit a gun shop (even a WalMart) and look at the books they have there. Pick up which ever one looks most like a phone book :-) and check the back section. If it looks like spreadsheets then you've probably found what you're looking for.

Anyway, if you're going to hunt with a gun you have to sight it in well and find out how accurate it (and you) will be at different distances. Then you can decide at what kind of range you'd be comfortable taking a shot at a game animal. If you can't hit the vitals with consistantly at 200 yds, then you don't take 200 yard shots. Not fair/ethical. So you figure what range is your maximum sure kill range. And you have to look at what your longest shot presentation is likely to be? 50 yds. in heavy woods? 500 yds. accross a bean field?

Then look at the ballistics tables to figure what distance you should sight in for so that you can hold dead on as far as possible without the bullet rising/falling out of the vitals area. Like I mentioned, this is maximum point blank range. IIRC, for a .30-'06, firing a 150 gr. bullet at 3000 fps, a MPBR sighting at 200 yds. will have the bullet at -1.5" at the muzzle, +1.5" at 100, hitting the crosshairs zeroed at 200 yds., and it will only fall 7" by the time it gets to 300 yds. Hold dead on all the way out to 300 yds. and you'll hit an 8.5" circle at any range (if you're doing your part).

If you can make a killing shot at longer ranges then you will have to practice at those distances and learn hold-over, at least, and probably reading the wind, dealing with mirage, parralax, etc.

Many ballistics charts will actually show the bullet rise/fall changes with the sights set at zero at different distances and help you figure out your maximum point blank range. Usually the first line will show "sighted at zero" or, in other words, the barrel held level. The next line will be "Zeroed at 50 yds." or so, and will show bullet rising 1/2" at 25 yds, at 0" at 50 yds., falling to -1" at 100 yds., falling to -4" at 150 yds., etc.

Good luck!

-Sam

 

Good info.
I don't slug hunt, we rifle hunt around here. Just curios about the 12gauge unsaboted slug accuracy/distance.

 

Standard slugs, fired from a smoothbore barrel, are usually done, accuracy wise, at 100 yards or less. Some claim small groups with smoothbore barrels, but most are lucky to group in a foot at 100 yards. Specialized slug barrels will do a little better, but 75 yards in is more like it for realistic shooting. This would include most police riot guns and most shotgun slug barrels for deer hunting that are smoothbore. Standard shotgun slugs are blunt and are designed to lose velocity pretty quickly, this to limit extreme range in the interests of safety in heavily populated areas. I guess some figure that if a gun doesn't shoot as far it is safer.

Rifled slug barrels, those that actually have rifling, and that fire slugs or sabots designed to take advantage of the rifling, do considerably better, as in 3 inches or less at 100 yards. Some sabot slug loads actually have trajectory/accuracy performance that make up to 200 yard shots possible.

I have the rifled type slug barrel for my Mossberg pump and an NEF rifled barrel single shot. I also handload slugs I cast myself in a few different slug moulds. It is hard to beat the accuracy of factory loaded sabot slugs, but the type I handload are much cheaper to shoot, so I get more practice in. Shooting more than a few dozen at a sitting will leave a pretty big bruise and a tendency to flinch, so I keep the practice sessions short to avoid the pain. Recoil in a lightweight shotgun (the Mossberg) starts to approach elephant gun recoil when they are fired at the higher velocities.

Shooting slugs with widely varying weights and velocities drives the point home that external ballistics alone do not fully explain varying points of impact with different projectile weights and velocities. Internal (interior) ballistics and an understanding of gun behavior while the bullet travels the length of the barrel are a very important part of explaining why bullets hit where they do, often when external ballistics says the very opposite should happen.