Long range shooting query

[edward hogan]

Seems like your initial question was addressing Ballistic Coefficients; with your remark about bullet weight and velocity.

Want to learn about bullet flight characteristics? Sierra Bullets and Berger are the real sources for detailed information. I have not read the Berger loading manual, but have owned and studied every Sierra book since manual #2. If you don't own the Sierra manual, buy a copy with their excellent Ballistics program, number 7 has just been released.

If you want a fast-track to results at longrange distances, meaning any distance past 600yds, look to the .243, .264, and .284 (6, 6.5, & 7mm) bore ctgs. 6mmXC probably the best choice due to ctg efficiency, mildest recoil, and high BC bullet numbers. Would say the .260rem is the next best turnkey solution and more cost effective as it is a .308win case variant.

You got a .308win? Seems most effective to shoot what you are currently setup with? Depends... Got a quality barrel to work with? If so, your choice is to invest in the ammunition to learn the .308win, or invest in a quality barrel in smaller bore ctg, and get finer accuracy from the start.

The Sierra 6.5mm 142gr matchking is basically the champ of small bore bullets. Berger likely has something of higher BC number, but Sierra is reliable. Shoot the 142gr smk with the Sierra accuracy load and you have a benchmark for excellence and an 80" advantage at 1000yds over the 175gr 30cal high BC bullets. Six feet, eight inches less drop; and gain in the wind also.

The same bullet at higher velocity makes for even flatter trajectory. 6.5x284 or 6.5 short magnum, even a .260rem Ackley Improved gives you appreciable velocity gain with the heavier bullets. Doing an AI chamber probably not so effective with 120gr or lighter bullets...

The .260 or .260 AI will result in best barrel life of those 6.5mm distance ctgs, and give you a much flatter learning curve than the .308win. Of course, if you can shoot a .300win mag or short magnum effectively those ctgs with 180/190gr match or VLD bullets will be close to same flat trajectory as the .260rem.

There are other consideration for equipment if .308win is chosen. Most scopes do not have elevation range of movement to get you to 1000yds w/o a canted scope rail. That adds another $160 or so to the equation. 20moa gain is not all that much when bullet drop, even with a 300yd zero is 350" at 1000yds for a 175gr from a .308win. Might be more drop depending on your actual velocity.

The 6XC and .260rem are the real beginner and expert choices for 1000yd shooting. For even longer distances the 6.5/284 or short magnums. There are other magnums as well for even greater velocity gains. More powder burned, less barrel life. Even the 6.5/284 has a barrel-burner reputation. If a $600 barrel is just part of the cost of getting into the game every 800rds, bravo! The 6XC should last 4x that number, in terms of gilt-edge accuracy. Study the ballistics and see the potentials.

[Bart B.]

Match winners and record setters do well to get 2400 rounds of 6XC barrel life. That's better than 1500 with the .243 Win. Not as good as 3000 with the 6PPC or .308 Win.

Good way to calculate barrel life is based on the cross sectional area of the bore diameter (not groove) in square millimeters. Cartridges with max loads of powder in grains equals bore area in square millimeters have about 3000 rounds of super accurate (match grade) barrel life. Increase charge 41% for a bigger case at the same caliber and barrel life goes to half; 1500 rounds. A 100% increase cuts it to 750 rounds. It's the old inverse square laws working. Double those barrel lives for ordinary hunting rifles; triple for combat service rifles. A bit more for powders with lower heat indices, less with hotter powders with high indices.

I also think that bore area in square mm's and charge weight for 3000 rounds is bore capacity. A 6mm bore capacity is about 28 grains. Cartridges using more charge weight are "over bore capacity." The .300 Wby Mag, for example.

I don't think there's any accuracy difference across all the cartridges mentioned above. They'll all shoot under 6 to 7 inches at 1000 yards from equal quailty rifles with properly reloaded ammo in stable conditions. That's as good as any rifle does. Those with lighter recoil are easier to shoot accurately, but their inheirant level's the same.

[edward hogan]

Here is a link to Canadian Dominion Rifle Club website.
http://www.dcra.ca/Marksman/Winter%2...%20Edition.pdf

The article to see in the Winter/Spring Newsletter of 2008 is "The New Challenge:90s in a .223" by Clint Dahlstrom. Essentially, the author recounts 1000yd results of 15-20 shot groups fired using JLK and Sierra 90gr VLD match bullets. Author used a bolt rifle, still his typical vertical spread at 1000yds is about 2.25" for most rounds landed. Horiz spread is also discussed, but was much more variable than the vertical spread.

A very interesting article outlining the capabilities of the minimal recoiling .223 ctg when fired with highest BC bullets. Of course, these results are over 6yrs old, maybe newer heavy bullets have been developed?

I will concede that inherent ballistic superiority means little from a fixed firing position on a known distance range which competitor has been able to zero rifle to and practice to learn the range conditions. Other more dynamic courses of shooting are fast becoming very popular in the tactical realm. To choose a .308win or most any .30cal or even 7mm chambered rifle in that venue means giving up some Ballistic opportunity to your competition.

The 6.5mm 142smk has .595 ballistic coefficient at 2850fps and above or .580 bc at above 2400fps. About as good as it gets until heavy .338s are considered then you can get .750bc maybe .800 with a 300gr Berger.

I asked myself why choose a .30 magnum when .338 at lesser velocity will do more. Same reason to choose a .260rem over a .308win. There are more ballistic variables to overcome with a lower BC bullet than a higher BC bullet if you want the same performance. The need to push at max loads may impart a lesser accuracy potential. Looking at the Accuracy Loads in the Sierra Manual, few of these, if any, are at highest velocity thresholds.

Do we push the velocity because we have to, as with Palma competition due to bullet restrictions, or do we choose the highest BC bullet and go with the lesser velocity, but best grouping load formula? I want as many variables in my favor as I can get. Flatter trajectory accomplishes much, especially when it comes with reduced recoil and muzzle whip. What does a 90gr vld JLK feel like out of a 12lb match rifle? Something like a CO-2 driven .177 pellet rifle at mild velocity, I suspect; or like no recoil at all...

I think the learning curve for longdistance shooting has to be less if you use a rifle that is easier to fire with consistency. Shooting medium range? Probably not going to matter as much, except for the recoil and barrel whip disturbance. To what purpose do we make it tougher on ourselves to learn?

[Jim Watson]

A 90 gr JLK .223 does not have much recoil at all out of a 14 lb F-T/R.
I know the BC and MV are very close to a 175 gr .308 but I never could get it to perform as well at Long Range.
It is a great little midrange rifle, though.

I could not drive a 90 gr Sierra fast enough to stay supersonic at a thousand, they tended to bend and break. Accurate when they held together but they didn't always. I had one string that was nothing but Xs, 10s, and misses.

The Bergers and JLKs are tougher.

If doing it again, I would get an 8 twist and shoot 80s at higher velocity.

[Pond, James Pond]

I appreciate the insight into calibre choices etc, but I'm not in a position to get another rifle and for reasons of ammo/component availability and choice as well as barrel life, .308 is probably the best choice for me.

As for scopes, I have a Burris XTR 312. Max magmification is a little bit less than I'd like, but it has lots of MOA adjustment (90Moa vertically IIRR), so I should be OK there.

I'm feeling quite positive about the Lockbase/N140 combo. Now at the moment the most I can shoot is 300m. This is close range in rifle terms, but I hope to find a longer range place next year. I've heard of some privately owned quarry where people can shoot. That is about 800m which is plenty!!

If I can get a load that seems to give good, tight results at 300, then I should be relatively well placed when I find that longer range place.

[Bart B.]

When the .223 and .308 competed against each other in 1000 yard service rifle matches at the Nationals, why were the .308's scores averaging higher than the .223's?

Was the US Army's decision to drop their .223 AR's and start using .308 AR's to start winning again a bad thing to do?

In the USA, Palma rifles can be either .223 Rem or .308 Win, why are the 22 caliber average scores lower than 30 caliber ones? The ranges are 800, 900 and 1000 yards using metallic sights and virtually all are bolt action.

[Jim Watson]

Because the little gun won't shoot as close to the wind as the big gun even though the numbers say it will.

Because pit people really hate looking for those little bitty bullet holes.

[edward hogan]

Again, reading J. Pond's initial post, his question goes to the matter of ballistics coefficient. What makes a 168/175 bullet fly more effectively at distance than a 155gr, was essentially his question.

Even though a .308win with Sierra 175 or Berger hot-rod 180gr bullet will "fly" 1000yds and remain supersonic (in most cases) by 50-80fps does this make for a Best Case selection to do the task?

To shoot 1000yds with the .308win with repeat precision, can we agree that some alteration to a standard, factory-produced rifle; unless a match long-range model, will be necessary? Not like a Rem 700 .308win BDL with a canted rail and high res scope will typically group consistently enough... So, in either paying for a rifle optimized for longrange or altering one to become so, there is a significant outlay of funds to enable the desired result. Then there is more fund outlay for ammunition or components.

Does it make sense, other than to comply with shooting-game rules, to choose a .308win for longrange shooting where precision is the goal?

My position is NO, although I own several so chambered and altered bolt and AR-10 rifles.

Takes a helluva lot of work to make an M14-M1a effective as a Service Rifle. The Armalite design with multi lug radial bolt and barrel extension lockup is much more capable than the two-lug opposed bolt design of the M14.

But what really matters is ballistic efficiency if cartridge choice is allowed.
J.Pond has the rifle he has. North of the Baltic may imply Europe or Northern Atlantic City. But if the .308win is the best he can access, the matter is settled.

Yet, if we look at the ballistic efficiency even at 800yds or less of more optimum ctgs, and weigh the financial outlays; is the .308win selection validated??? If compare the .595/.580 BC of the 142gr SMK with the .505/.498 BC of the 175gr SMK, along with potential velocity gains, which selection is most validated if Longrange precision is our goal?

Does the .308 case, when necked to .264 id yield greater propensity for precision at longrange distances in excess of 600yds? All variables held equal, the answer has to be YES, because the bullet flies with potential of 49" less drop at max distance. The 50" gain in trajectory is material and also translates into better wind effectiveness.

As to ctg selection if 1000yd precision is the goal, the 6.5/284 at 2950fps vs the .308win 175gr at 2600fps shows about 150" of ballistic advantage. More recoil from greater powder charge, of course. But if recoil is manageable and barrel life a cost of doing business, why choose otherwise? Would choose a .30magnum instead? No real reason to.


The .260rem offers a 100 - 150 fps velocity gain over the standard .308win,
The .260rem AI offers 6.5/284 velocities in the 2900-3000fps range with 142gr SMK. At 2800fps the 142smk gets into its .595 bc realm. Lots of shooting performance is a headgame. If you work the best performing ctg your performance is likely to improve or come up to the challenge all other factors being equal.

[Jimro]

Bart B., I'm pretty sure you were asking a rhetorical question, but your questions actually do have answers.

When the .223 and .308 competed against each other in 1000 yard service rifle matches at the Nationals, why were the .308's scores averaging higher than the .223's?

Key word is "Service" in service rifle. Beyond 600 you can't keep a 223 going with the 308s using either the AR10 or M1A. 20" barrels is all you get for the 223, and you get 20 or 22 with the 308.

Was the US Army's decision to drop their .223 AR's and start using .308 AR's to start winning again a bad thing to do?

No, it was a great thing to do. But you'll notice that no one is giving up their AR-15s for the 200, 300, 600 High Power service rifle matches.

In the USA, Palma rifles can be either .223 Rem or .308 Win, why are the 22 caliber average scores lower than 30 caliber ones? The ranges are 800, 900 and 1000 yards using metallic sights and virtually all are bolt action.

Because it is easier to make a long range load with a 308. a 1/10 powder charge spread in 308 is statistically very small. A 1/10th powder spread in 223 is at least twice as statistically significant, even if the overall effect is still relatively small. Primer consistency is another area where the 308 has an advantage, the same real spread in priming compound weight will have a much higher statistical effect on the smaller primers. This is one of the reasons small rifle primers in 308 cases haven't taken Palma by storm, the consistency really isn't there for 800 plus yard shooting.

So on paper the 223 looks like a no brainer, as long as primers and powder and case volumes are mathematically perfect. But reality isn't mathematically perfect. At 600 and under those imperfections aren't hurting scores, at 800 and beyond they are. A +/- 1% spread in muzzle velocity for a bullet going 2750 fps gives an extreme spread of 45 fps, which is not really acceptable for 1000 yard shooting. That same spread at 600 yards is still within the 10 ring if everything else is on point.

Jimro

[Bart B.]

Jimro, good responses.

The only thing these days beating the .223 AR's in matches at 600 yards or less is the 6mm Tubb2000 and Eliseo bolt action tube guns. M1's and M14/M1A 30 caliber heavier kickers cannot be shot as accurate even though their accuracy's about the same as the AR's.

[4runnerman]

Jimro, good responses.

The only thing these days beating the .223 AR's in matches at 600 yards or less is the 6mm Tubb2000 and Eliseo bolt action tube guns. M1's and M14/M1A 30 caliber heavier kickers cannot be shot as accurate even though their accuracy's about the same as the AR's.

Bart I am in the dark here-Please explain.I shoot 300 to 1200 yards in matches now for 2 years. Not once has a 223 in bolt or AR ever won. We must be talking a different kind of shooting. I am taking FTR and F Class open.

Winners are 308,30BRX,6BR's 6.5's ect ect, Never a 223

[Bart B.]

I'm referring to service rifle matches where 22 and 30 caliber semiauto's are the only rifles used. They're outscored by larger caliber bolt guns. Shoulda said that, coulda said that but dinna say that. Sorry for the confusion.

One big contributor to the 22 caliber failing past 600 yards is the long, heavy bullets' big drop in BC as they slow down to under 1800 fps. Sierra's heaviest HPMK's are the worst. Here's Sierra's 90 gr HPMK:

.504 @ 2200 fps and above
.511 between 1900 and 2200 fps
.500 between 1750 and 1900 fps
.467 between 1575 and 1750 fps
.400 between 1375 and 1575 fps
.305 @ 1375 fps and below.

If someone's got Sierra's latest software and would run it with this bullet leaving at 2650 fps in 70 deg. temperature at 500' altitude to see where it goes subsonic and it's 1 mph wind drift at 1000 yards, then post the numbers, kudos to him.

[Metal god]

MY cheap calc says the 80gr smk leaving at 2650fps goes subsonic right around 900yds and has a 12.4" 1mph wind drift @ 1k . FWIW the bullet will drop almost 455" or about 38 feet

[Jimro]

4Runnerman,

Bart I am in the dark here-Please explain.I shoot 300 to 1200 yards in matches now for 2 years. Not once has a 223 in bolt or AR ever won. We must be talking a different kind of shooting. I am taking FTR and F Class open.

Winners are 308,30BRX,6BR's 6.5's ect ect, Never a 223

F Class targets have smaller scoring rings than High Power targets, and generally F Class is shot at a longer distance than a cross the course High Power match, although midrange F Class uses 500/600 yard targets. Technically F Class is a "High Power" derivative, but since they use different rules, different targets, and allow optics and bipods they are really two different sports.

What Bart B. was talking about is that in Open class High Power the 223 isn't the king, only in Service Rifle class, and not because it is more inherently accurate than the 308, but because the mild recoil makes it easier for the shooter to shoot accurately. Especially since you only get a jacket, glove, and sling to to help you shoot, no scope or bipod.

To borrow a phrase from Tam, AR-15s are "stupid easy" to shoot well, and you see more of them on the line because you can put together two AR-15 match rifles for about the cost of one M1A supermatch, and they are cheaper to feed with either handloads or commercial match ammo. They are also a much better platform for training our Juniors on for both weight and ergonomics (it is still a legal modification to put an A1 buttstock on to reduce length of pull for smaller shooters).

I rarely see 308 win in F Open, but generally the 308 shooters beat the 223 shooters in F/TR class, for the same reasons Palma shooters use the 308 and not the 223.

Bart B.,

I used JBM to get this, using Bryan Litz's data for the 90 SMK.

90gr SMK, 2650 fps, 500 feet altitude, 70 degrees F, 1 mph wind.

36.5 MOA to 1k, 9 inches of drift per 1mph wind passes the sound barrier after 1050 yards.

But it hits the transonic region between 850 and 900 yards, so a shooter might have issues with accuracy.

Jimro

[Bart B.]

Jimro, thanks for the ballistics info.

Gonna buy Sierra Infinity software today. It uses their several BC's instead of one as Litz' all others do. That, to me, means that 90-gr bullet's BC drop to 60% of what it started out with in 1000 yards of flight cannot have the same trajectory as one with a constant BC.

Note bullets start misbehaving a bit before they reach their transonic speed. So the ones most susceptible to trajectory changes do so a short distance before the exact transonic range is reached.

[Metal god]

It uses their several BC's instead of one as Litz' all others do. That, to me, means that 90-gr bullet's BC drop to 60% of what it started out with in 1000 yards of flight cannot have the same trajectory as one with a constant BC.

Because of this . I've never used the highest BC for a given bullet . I always input the mid range BC into the calc in order to get what I think would be a more realistic calculation

80gr smk
.420 @ 2200 fps and above
.400 between 2200 and 1800 fps
.393 @ 1800 fps and below
I input a BC of .400 because the bullet will travel at all of those velocities out to 1k .

The 90gr smk with a BC of .480 i get pretty much the same numbers as Jimro except my calc saws the bullet never goes subsonic . At 1k it's velocity is still 1237fps 900yds 1334fps

When you get the program please come back and post your results

[Jimro]

Bart B.,

Litz's data uses the G7 reference model, which equivalently maps the multiple BC's of the G1 model that Sierra advertises. The JBM software that has (Litz) next to the projectile is the data that Litz gathered testing the bullet in real conditions.

Either method of predicting ballistic performance will work just fine.

Jimro

[Jimro]

Metal God,

The 90gr smk with a BC of .480 i get pretty much the same numbers as Jimro except my calc saws the bullet never goes subsonic . At 1k it's velocity is still 1237fps 900yds 1334fps

The calculation doesn't show subsonic until after 1k, but the "transonic region" is about Mach 0.8 to 1.2. The 90 SMK hits Mach 1.2 at 900 yards in that ballistic solution, so you can't always expect stable performance through that velocity.

For example, ever wonder how a subsonic 168gr SMK load from a 300 Blackout can have a very stable BC across the usable range of the load? By starting out subsonic the bullet drops down into a stable BC and stays there. Google "wave drag transonic" and click on the images to see the increasing drag on a solid body in the transonic region, which is why Sierra shows higher BC's for higher velocities.

Ballistics is fun stuff :P

Jimro

[Metal god]

Thanks Jimro . I always assumed as long as the bullet was above 1200fps you were gtg .

[Bart B.]

As Sierra established their G1 numbers from time of flight tests with many velocities, I don't see how a fixed G7 number will yield the same results as multiple G1 numbers.

Gotta get Sierra's Infinity software then compare it with Berger and JBM software for the same bullet.

[Jim Watson]

There is more difference between G1 and G7 than just a different number to start out with. The calculations to use them are different. In earlier times, there were huge tables to look up drag functions. I don't know if the computer programs now use digital lookup tables or if they use approximating equations. Maybe Mr Litz says which in his book, I can't find it in his articles.

See the article at
http://www.bergerbullets.com/a-bette...c-coefficient/

The key point is
It’s a relatively well known fact that the BC of a bullet is different at different velocities. Not many shooters know why it changes, or what the consequences are. To understand why a BC changes at different speeds, we have to go back to the definition of BC, which is: The ability of the bullet to maintain velocity, in comparison to a ‘standard projectile’. It’s the ‘standard projectile’ part of the definition that we need to key in on. What is the ‘standard projectile’? What does it look like?

To date, the ‘standard projectile’ used to define BCs for the entire sporting arms industry is the G1 standard projectile. The G1 standard projectile which is shown in Figure 1 has a short nose, flat base, and bears more resemblance to a pistol bullet or an old unjacketed lead black powder cartridge rifle bullet than to a modern long range rifle bullet.



The reason why the BC of a modern long range bullet changes so much at different velocities is because modern bullets are so different in shape compared to the G1 standard that its BC is based on. In other words, the drag of a modern long range bullet changes differently than the G1 standard projectile, so the coefficient relating the two (the ballistic coefficient) has to change with velocity.

There are several ways to manage the problems caused by the dependence of BC on velocity. One way is to use a G1 BC that’s averaged for the speed range you’re interested in. This will get you close, but what if the BC of the bullet is advertised for a speed range that’s different than what you’re interested in? It’s not easy to adjust the BC for different average velocities. Another way to deal with the problem of a velocity dependant BC is to give the BC in several velocity ‘bands’ (Sierra bullets uses this approach to advertise the BCs of their bullets). This can be an accurate approach, but it leaves a lot of room for misinterpretation. For example, many shooters don’t understand why there are different BCs and choose the wrong one. Furthermore, not all ballistics programs allow you to input multiple BCs. In short; the use of the non-representative G1 standard (Figure 1) to define BC is responsible for the velocity dependence and associated problems with BCs.

A better standard for long range bullets
If you look at the G1 standard projectile again in Figure 1, you might think; “it’s too bad there isn’t a standard that’s more representative for modern long range bullets”. In fact, there are several standard projectiles, all with different shapes, that are much more representative of modern long range bullets than the G1 standard. The standard that bears the closest resemblance to most modern long range bullets is the G7 standard, shown in Figure 2.

As you can see, the G7 standard projectile, with its long boat tail and pointed ogive bears a much stronger resemblance to a modern long range bullet than the G1 standard projectile. As a result, the BC of a modern long range bullet that’s referenced to the G7 standard is constant for all velocities! In other words, a trajectory that’s calculated with a ‘G7 BC’ doesn’t suffer from the same velocity dependence problems and inaccuracies as calculations that are made with a G1 BC.


Sierra gives a lot of history and the basis for their use of G1 BC by velocity brackets
http://www.exteriorballistics.com/eb...oefficient.pdf

The ballistic coefficient of a bullet is a scale factor (a number) which divides the standard drag to predict the actual drag on the real bullet.

A standard drag function (G1, G7, etc.) is a table of numbers. Each pair of numbers in that table are (1) a specific speed of the bullet in the air, and (2) the drag deceleration of the standard bullet at that bullet speed, divided by that bullet speed.

Ballistic coefficients are relatively easy to measure in a shooting laboratory. The technique is to measure initial velocity and final velocity of each fired round (using chronographs) over a measured range distance between the chronographs. Then a software analysis program is used to compute the ballistic coefficient value which would cause the standard bullet starting at the initial velocity to have a computed final velocity equal to the measured final velocity.

Because a ballistic coefficient always relates to a specific standard drag model, say G1, that ballistic coefficient cannot be used with any other drag model, say G7.

[Bart B.]

If the .223 Rem is such a great tack (or pin) driver for distant targets, why ain't it popular with long range group and score match winners shooting bolt action rifles?

Could it be they're still in the dark about what's best and have problems finding their ammo when it's too tiny and can't be easily found in low light situations?

[tobnpr]

Could it be they're still in the dark about what's best and have problems finding their ammo when it's too tiny and can't be easily found in low light situations?

Yeah- Yeah! That must be it!

I'm going to pull a very nice Rem 700 in .223 out of it's mothballs in the gun cabinet now for the next range trip!!

[Bart B.]

After much ado about trivial stuff, finally got my Sierra software.

Gonna run it versus Bergers for the same bullet at one muzzle velocity and environment to see what the differences are.