bullet weight vs bullet diameter

[Vurtle]

First post so take it easy on me.

If you have a 243 win and a 308 win and both are shooting similar 90gr bullets, What is the difference? Will they do the same damage or does the bigger diameter cause a significant damage difference?

I realize most people aren't using 90 grain 308 bullets. I currently load 243 100gr and I am considering purchasing a 308 barrel for my encore. I am recoil sensitive and I understand the 308 with a 90gr bullet has similar recoils. My hunting is mostly Texas whitetail.

 

[adobewalls]

Depends on velocity.

If velocity is the same; then theoretically the .243 would perform better because it would possess greater sectional density than the .308. The greater sectional density for the .243 would translate into a higher ballistic coefficient and, theoretically, better capability to penetrate.

The world, however, is not that simple.

 

[helotaxi]

Don't bother trying to shoot a deer with a 90gn .308 bullet. Totally inappropriate bullet for the job. 150gn is about the lightest bullet properly constructed for deer.

If you're recoil sensitive and you want a better deer cartridge than the .243 (which is perfectly adequate) look at the .260 Rem.

If you're reloading and shooting an Encore, consider the 30/30 if you must have a .30 cal. Since you don't have to worry about them sitting in the magazine, you can load spitzer bullets and thus stretch the range of the 30/30 a decent bit.

Why do you want a different caliber? What ranges are you planning on hunting at?

 

[adobewalls]

Just for grins I pulled out Bryan Litz's Book, Applied Ballistics for Long Range Shooting and looked up the Matuna Optimal Game Weight Formula and fired up my spreadsheet.

The comparison isn't apples to apples because the closest reloading book I had to reference was an old Sierra Manual, so I could only compare 100 gr. .243 to a 110gr. .308. But here goes:

.243 with 100gr. at 3,000 F/s compared to a .308 with 110gr. at 3,000 f/s.

Matuna OGW formula: OGW = V^3*W^2*1.5X10^-12; Velocity is f/s; W is grains and the 1.5x10^-12 takes care of the units.

The .243 velocity from muzzle to 400 is: 3,000; 2,763; 2,531; 2,312; 2,103
The .308 velocity from muzzle to 400 is: 3,000; 2,752; 2,525; 2,309; 2,103

The formula results for optimum weight of animal from muzzle to 400 is:
.243, 100gr., 3000f/s: 405#; 316#; 243#; 185#; 140#
.308, 110gr., 3000f/s: 490#; 378#; 292#; 223#; 169#

So, it appears the .308 wins the math contest due to the 10 extra grains of weight; if the weights were the same the .308 would lose because the .243 retains its velocity better out to 400 yards. HOWEVER; I agree with Helotaxi; 90 gr./110gr. .308 bullets are usually varmint or plinking bullets and are not designed for hunting animals even the size of small Texas deer.

 

[788Ham]

helotaxi, I believe if you read the beginning of the second sentence, it starts "IF".

 

[Vurtle]

So if velocities are the same, why would the 90 gr in a .243 be considered a good deer bullet and a 90 gr in a .308 not be? I am assuming here, but wouldn't energy be the same too? I think this may become a can of worms thread.

I am looking at getting a 308 barrel incase I ever venture to hunt bigger animals. Max range ever for me is 200 yd.

 

[benEzra]

So if velocities are the same, why would the 90 gr in a .243 be considered a good deer bullet and a 90 gr in a .308 not be? I am assuming here, but wouldn't energy be the same too? I think this may become a can of worms thread.

Because if the fatter .308 bullet is the same weight as the relatively skinny .243 bullet, the former must either be a lot stubbier (less sectional density = less penetration) or else it must have a big hollow cavity up front (more fragile construction = less penetration). Either way, a 90-grain .308 bullet will penetrate less than a 90-grain .243 bullet, and will lose energy more quickly in flight due to greater drag for its mass.

 

[Vurtle]

So I think I understand the sectional density lingo. I found this on the web just now. So this means a .358 200 gr has less killing ability than a .243 100 gr because of sectional density? Is this correct (assuming same velocity and bullet design)? So mathematically, a 243 115 gr has better penetration ability than a 460 400 gr at the same velocity? Which I doubt a 460 would push anything close to a 243 velocity?

My goal is to not be an ignorant hunter so please bare with all the questions.

http://www.chuckhawks.com/sd.htm

 

[GooseGestapo]

There are other factors in play.
Velocity and mass don't tell the entire story.

Bullet velocity and mass affect the final energy available. With enough weight (mass), and velocity, you can take out a tank. (ie: 120mm gun on Abrams M-1 tank fires a 12lb depleated Uranium "dart" at a m/v of about 5,100fps. It penetrates as much as 6" of hardened steel armor, turns into a "plasma" (molten metal) as it penetrates and then spews red-hot spray mist of heavy metal inside the cavity inside the turret.......think buck-shot, 12lbs of it, at ~2,000deg F. Nasty piece of ordanance.....

A .358win with a 200gr bullet at 2,400fps has somewhat more momentum, a different mathmatical formula,than the .243 and will not neccessarily penetrate further than a .243 but imparts a lot more energy to the target due to greater mass and bullet diameter. Bullet construction plays into the issue as well..... hardness of bullet metal (lead alloy) and thickness of bullet jacket...

What has more "torque"? A 400 horsepower 2-liter gasoline engine (ie: .243) or a 400hp 8.0l diesel truck engine? ie: 416 RemMag. Both car engines turn out 400hp, but the diesel engine will haul several tons of gravel much more efficiently than the 2-liter "rice burner" engine, though it will make a 2,000lb car go very, very fast.

Question is how much "work" will they do. A .416 Remington Magnum with a 400gr bullet at 2,400fps does a LOT more work than a .243 with a 100gr bullet at 3,000fps. Kinetic energy figures are near meaningless unless comparing two very similar items, such as a .30/06 with a 150gr bullet, vs. a 220gr bullet. The 220gr load makes a decent moose and brown bear load, a .243win with a 100gr load might get you stomped or bitten...... And then we start talking about shot placement, shot placement, shot placement......

 

[bhk]

In real life, you also need to look at bullet construction. If you were using cast lead bullets or fmj bullets for the comparison, this would not be an issue. Commercially available jacketed 'light-for-diameter' hunting bullets are usually constructed with very thin jackets and designed for varmints. They may explode on impact, or at least come apart easily and not achieve satifactory penetration for humane kills. 'Heavy-for-diameter' bullets usually have heavily constructed jackets and other designed features that encourage delayed bullet expansion and deeper penetration. 110 grain .308 bullets are certainly not deer bullets. You would be much better off with a 100 grain bullet in the .243 for deer.

 

[DM~]

In real life, you also need to look at bullet construction. If you were using cast lead bullets or fmj bullets for the comparison, this would not be an issue. Commercially available jacketed 'light-for-diameter' hunting bullets are usually constructed with very thin jackets and designed for varmints. They may explode on impact, or at least come apart easily and not achieve satifactory penetration for humane kills. 'Heavy-for-diameter' bullets usually have heavily constructed jackets and other designed features that encourage delayed bullet expansion and deeper penetration. 110 grain .308 bullets are certainly not deer bullets. You would be much better off with a 100 grain bullet in the .243 for deer.

This is absolutely the most important answer. Bullet construction is everything, and that's why you can NOT compare bullets of the same weight, let alone of a different diameter!

The other answers qiven are valid and useful, but construction is the most important.

DM

 

[benEzra]

So I think I understand the sectional density lingo. I found this on the web just now. So this means a .358 200 gr has less killing ability than a .243 100 gr because of sectional density? Is this correct (assuming same velocity and bullet design)? So mathematically, a 243 115 gr has better penetration ability than a 460 400 gr at the same velocity? Which I doubt a 460 would push anything close to a 243 velocity?

Sectional density determines the penetration ability of two different bullets of similar weight. The example of a 90-grain .243 vs. a 90-grain .308, for example.

If two bullets are of dramatically different mass, though (say a 77gr .223 and a 180gr .30-06), then the mass difference is going to matter. Generally speaking, heavier bullets penetrate more, given similar sectional densities.

 

[Art Eatman]

Bullet design must be considered. The 90-grain bullets in .243 are generally intended for deeper penetration than, say, a 55-grain bullet. The former are intended for deer hunting; the latter for varmints, and they tend to disintegrate upon initial impact.

In thirty caliber, bullets of 110 grains and lighter are not intended for deep penetration. They "blow up", disintegrate, upon impact. The common deer bullet in thirty caliber is the 150-grain.

For any design of whatever sort in a particular caliber, a heavier--i.e., longer--bullet will penetrate more deeply than a lighter bullet.

Think about ol' Mo Mentum. To exaggerate a wee tad, compare a freight train with a blimp.

 

[helotaxi]

The .243 velocity from muzzle to 400 is: 3,000; 2,763; 2,531; 2,312; 2,103
The .308 velocity from muzzle to 400 is: 3,000; 2,752; 2,525; 2,309; 2,103

Those numbers are off by a good bit. Comparing the .308 110gn V-Max (one of hte best ballistically in that weight and caliber) and the .243 100gn BTSP the velocity spread is pretty significant at 400yds. The difference of 0.115 in BC is pretty significant (40%).

I got
.243: 3000 - 2768 - 2548 - 2340 - 2142
.308: 3000 - 2680 - 2382 - 2105 - 1847

OGW works out to:
.243: 286 - 212 - 165 - 128 - 98
.308: 327 - 232 - 163 - 112 - 76

So assuming that the .308 bullet were indeed suitable for medium game (which it isn't) the .243 becomes superior (based on the OGW formula alone) inside of 200yds. Factor in sectional density and bullet construction and the .243 is the better choice at every range if limited to those bullet weights. And technically the .308 would have slightly more recoil.

A skinny bullet with high SD and the higher BC that usually goes with it is going to give you better performance across the board on game and have less recoil.

 

[mshootnit]

That 90 grain 243 bullet will probably penetrate better but a 90 grain 308 bullet could theoretically be pushed to higher muzzle velocity. However it would quickly lose that advantage and I don't think a 90 grain 308 bullet would be very stable to begin with. Maybe a 100 yd round or something like that. A 90 243 bullet on the other hand is good to 400-500 yds.

 

[helotaxi]

Stability would actually be excellent on the light weight .308 bullet but it really is like shooting a .177 cal airgun pellet downrange. It is such a ballistic pig that it will rapidly shed velocity and drop like a rock as well as being extremely wind sensitive. The 110 V-Max with a 3k FPS MV would hit the transonic range slightly past 500yds and it's hard to say what it would do then from a stability standpoint.

 

[Art Eatman]

Re-reading the opening post: Vurtle, if you're sensitive to recoil, why mess with the .308? You already have as good a deer cartridge as you'd ever need.

I've killed some two dozen cenTex whitetails with the Sierra 85-grain HPBT out of my little Sako Forester carbine, going mostly for neck shots or cross-body heart/lung shots. Never had any of those deer go anywhere but down to the ground. (I always avoided angling shots through the body.)

Seven-pound rifle; never have noticed the recoil, particularly, even from the benchrest...

 

[BrocLuno]

Same weight, different calibers (diameter) means one is longer than the other. Longer means sleeker which means better flight characteristics

 

[gamestalker]

If your recoil sensitive, and are simply wanting something to hunt deer with, just stick with a .243. I have an old friend that is a long time guide who is blind in his right eye. He doesn't tollerate recoil well shooting off his left shoulder so he has been hunting with nothing but a .243 since the bigining of time, so to speak. LOng story short, he has had no problem efficiently killing deer, antelope, black bear, elk, big horn sheep and probably a bunch I have forgot about. The .243 has been under rated since it's introduction and without merit.
The answer to your delema is shot placement. A 105 grain projectile of good design will easily dispatch most North American game with good shot palcement. If your still feeling under gunned then pick up another barrel but I really don't think you'll be satisfied with a .308 varmit bullet as a deer killing combination, and some would even consider that as being risky at best.

 

[Arkansas Paul]

What Art said in post 13. Spot on.

 

[MachIVshooter]

If you summarize all the replies here, you get a pretty good answer to your question.

More importantly, as Art said, you have more than enough gun for whitetail deer. Any cartridge burning more powder and/or launching heavier bullets is going to generate more recoil that just isn't necessary for such small animals. If you decide you'd like to pursue monster mulies or elk, then you may want to revisit the .308 (or any number of other medium cartridges in the .257"-.308" range), as 6mm bullets and the cartridges that propel them are definitely on the light side for 400+ pound game.

 

[nelsonal]

The bullet with the smaller bore will be considerably longer and thus for most bullets will retain more energy at distance. You can see the extreme of this with match ammo being very, very heavy for caliber (77gr for .223 for example). Depending on your gun, you might also have problems with stablilization either over stabilizing the short, light bullets, or understabilizing the heavy, long bullets.

However, since all bullets aren't just cast lead, and as others mentioned bullet construction becomes quite important. Most of the light for caliber bullets are intended for smaller rounds and lower velocities and usually smaller animals, some specifically designated for varmint applications. What this means is when you're 90gr 308 bullet hits your target, it's much more likely to break apart rapidly with no parts large enough to penetrate effectively (because it was designed to do that or perhaps to expand normally at much lower velocities).

If you can find a light for caliber bullet that is designed for the application you seek, then be cautious about long shots because the bullet isn't going to retain as much energy as the normal weight bullets.

 

[helotaxi]

The bullet with the smaller bore will be considerably longer and thus for most bullets will retain more energy at distance.

This is captured by the ballistic coefficient.

You can see the extreme of this with match ammo being very, very heavy for caliber (77gr for .223 for example).

This shold be clarified as "long range match bullets." Short range bencrest type bullets are usually on the lighter side of the middle weight for caliber.

either over stabilizing the short, light bullets

Myth. A bullet is either stable or not. You might induce a bullet failure in flight by spinning one apart, but that isn't a stability problem. The bullet is very stable when it flies apart

 

[Vurtle]

Thanks for all the input. The sectional density is the eye opener for me. Never thought of a bullet's ability in that manner. It makes sense why an arrow can do what it does now. It appears I will probably purchase a 260 rem or 7mm08 if I ever need something bigger and has minimal increase in recoil.

I currently load 100gr hornady interlocks for the .243 and they have good accuracy with imr4350. Only shot em at the range though so I'll see how they work this season.