what cals are flat ?

tjhaile, that's interesting; I've duplicated your results, and I don't understand yet what the reason is.

I used JBM (www.jbmballistics.com) to run two cases
1 - BC=0.400G1, MV=2750fps.
2 - BC = 0.285G1, MV=1300fps.

In both cases, I turned off "elevation correction for zero range", so it was fired with the muzzle horizontal.

In case 1, the bullet arrived at 500 yards in 0.690s, falling 79.2" below boreline.

In case 2, the bullet arrived at 257 yards in 0.691s, falling 84.5" below boreline.

Puzzling......

tjhaile said:
Let's see what actual ballistics calculations can tell us. I found this external ballistics calculator:

http://www.handloads.com/calc/

Bullet #1: Weight of 150 grains, BC of .400, MV of 2750 fps
Bullet #2: Weight of 405 grins, BC of .285, MV of 1300 fps

In both cases, I have used the following inputs for both:
-Sight in range of zero
-Sight height on zero
-Zero muzzle elevation
-10 mph wind at 90 degrees to bullet path
-Sea level altitude
-65 F ambient temperature

Maximum distance used is 500 yards with 10 yard increments

Bullet #1 traveled the entire 500 yards in 0.69 seconds and dropped 79.82 inches below line of sight.

Bullet #2 traveled 257 yards in the same time period and dropped 85.2 inches below line of sight.

It does appear that there can be a substantial difference in bullet drop for a given time between two bullets with different weights and BCs.
Click to expand...
 
For comparison, we can expect an object dropped (or fired horizontally) in vacuum to fall a given distance in a given time as follows:

s = 1/2*at^2

Where s is the distance, a is acceleration due to gravity (32.17 ft/s^2), and t is time. Using this formula, we can expect the object to fall 7.88 feet or 94.6 inches using the time of flight of 0.7 seconds.

I think what is actually happening here is the low BC bullet sheds velocity more rapidly, causing the nose to point down at a greater angle than the high BC bullet after the same time interval. As a result, a greater proportion of the low BC bullet's motion is in the vertical plane relative to the earth's surface. While the overall drag (both vertical and horizontal components) on the high BC bullet is lower, the vertical component of its drag is greater than the low BC one, because its point is not facing down to the same extent.
 
AKD said:
not asking cus im buying just curious. One of my guns is a 22-250 and a friend has a 270. I always find it impressive how flat there trajectory is.

it got me wondering, what round seams to drop the least ...... lets say out to 500m
Click to expand...

5 minutes with any decent ballistics program would answer your question.
Many of the supposedly flat shooting calibers like 270 are fine out to a given distance, but at longer range do not come close to what some other calibers can do.
 
Confusing thread is confusing.:confused:















:confused::confused::confused:
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To really determine what is "flat shooting" 1 should look at how many MOA are really needed to get to a given distance.
I would propose that given a balistics program is not used, some of could post what we need with our caliber of choice to get to 1000 yards, and I am taliking verifyable in the real world.

Shooting 300 gr SMKs my 338 LapuaAI gets 3050 fps and needs 19.5 moa to zero at 1000 yards given a 100 yard zero.
Shooting 190 gr SMKs out of my 308 Win gets 2685 fps and needs 31.5 moa to zero at 1000 yards given the same 100 yard zero
No brainer the 388 is WAY flatter shooting, so now lets see who else can post similar data and hopefully the original question can be answered.
 
AKD said:
Witch cals produce a really good fast flat trajectory with a thin but yet very high kinetic energy round?

is 7mm the king ?
Click to expand...


Didn't read all three pages but the answer is simple.

Take the heaviest highest BC bullet and send it the fastest and Voila, you have the flatest shooting combo with the most horsepower.

At one end you have the 50BMG with the highest BC bullets AND lots of horsepower. However, the BMG is not particularly fast so you still to crank up on the scope the further you go.

The flatest given what MAY BE produced and easily duplicated, would be the 338-408CT improved in a 36" barrel pushing the still in R&D 300gr Berger VLD's (yes 408 CT brass IS readily available).

We know that this monster case WILL push 300gr MK's to 3400fps with decent accuracy and the bullets don't blow up in flight. G1 BC is 0.745 and G7 BC is 0.381.

The Bergers in development have a proposed G1BC of 0.914 and G7BC of 0.468. Push these to the same velocity and you have something that is flatter then ANY known workable wildcat.

Necked down BMG's have been tried with very limited success. NO the 416Barrett doesn't come close as the printed BC of these bullets is not particularly exciting.

The key is the maximum velocity the bullet can go before grenading. Hopefully, the Berger VLD's will prove as durable as the MK's.

The best resource I have read is the new Bryan Litz book (yes, I know I sell it but it really is a superb resource - why I sell it;)). It covers so many of these topics with proper testing and analysis. This is the only place where there is standardized testing of bullets to get a comparable BC values. The included Ballistic software alone is worth as much as the book (more from some companies).

There question answered.

Now the most practical/affordable and accessible choice IS a 7mm.

The Berger 180gr VLD has a G1BC of 0.659 and G7BC of 0.337 which puts it right near the top of low drag bullets. It is a no brainer to get it going to 3000fps in a 26" to 30" barrel and the LR accuracy/driveability is amazing (yep, been there, been amazed).

I have yet to hear how fast it can go before puff but would guess 3200fps as workable. That would make for a very flat shooter that will also hit with authority.

Anyone want to build a 32" 7RUM and see what happens?????

Now I have heard from a reliable source that Berger is also thinking about developing 30cal bullets with the same geometry as the 7mm 180gr Berger. These bullets would certainly split the difference between the 7 and 338 and make alot of 300WM and RUM shooters very happy.

SWAG would be 235 to 240gr VLD with a BC well over 0.8. Or I could use the formulas in Bryans book and get a really close estimate:D

Jerry
 
Jerry's got it nailed exactly.

There isn't a "top of the line" .30 cal bullet out there yet (by which I mean a .30 cal equivalent to a 140-class 6.5mm bullet, or a 180-class 7mm bullet, or 300-class .338 bullet). Scaling those to .30 cal (look to Bryan's book, which is simply standard cube/square/linear scaling laws), you get a 230-ish grain .30 cal bullet, with a bc that is (7.62/7) = 1.089 times as much as the 7mm bullet (so bc=0.717G1 or .337G7). To get the same velocity as the 7mm, you'll need (7.62/7)^3 = 1.29 times as much powder capacity as the 7mm case.
 
I have alway liked playing with 7mm and 6.5 mm bullets for long distance, they have High BCs.

But since I have been shooting a 50, its a new world, at 1.4 Km 39 MOA with a BC of 1.15, thats pretty flat shooting compaired to anything I have shot prior.

As mentioned the 338 projectile, is good, but I think the best out there right now is the 408 CT.

Look for elevated velocities, and High BCs to flatten out the trajectory. Depending on what use you are going to apply the bullet too, these may be out to lunch. If for hunting the 338s, and 7mms make good pills for LR hunting.
 
JasonYuke said:
I have alway liked playing with 7mm and 6.5 mm bullets for long distance, they have High BCs.

But since I have been shooting a 50, its a new world, at 1.4 Km 39 MOA with a BC of 1.15, thats pretty flat shooting compaired to anything I have shot prior.

As mentioned the 338 projectile, is good, but I think the best out there right now is the 408 CT.

Look for elevated velocities, and High BCs to flatten out the trajectory. Depending on what use you are going to apply the bullet too, these may be out to lunch. If for hunting the 338s, and 7mms make good pills for LR hunting.
Click to expand...

Actually the 408 has no where near the BC of what the better 50 cal projectiles do. The added weight that the 50 has coupled with the higher BC bullets still give the 50 a very distict long range advantage. much the same as what the 408 enjoys over the 338s
 
well there ya go! learn something new everyday..

Not much info on the CT out there.. I hear accuracy is amazing

Ya I guess a BC of over 1 found on the 700 gr Amax is hard to beat. I have calculated it backward from shooting, and found these Amax projectiles are about 1.15, work bang on for me.

There is nothing like a 50,,,just nothing
 
JasonYuke said:
well there ya go! learn something new everyday..

Not much info on the CT out there.. I hear accuracy is amazing

Ya I guess a BC of over 1 found on the 700 gr Amax is hard to beat. I have calculated it backward from shooting, and found these Amax projectiles are about 1.15, work bang on for me.

There is nothing like a 50,,,just nothing
Click to expand...

Unfortunately the guys at Cheytac were bigger on bragging up the atributes of the 408 than they were in making apple to apple comparisons and actually making the performance gains they were claiming, which is why to a degree they have only marginal credibility.
Marketing hype does not always make the claim so. And physics is still a given set of laws that are hard to change.
 
AKD said:
Witch cals produce a really good fast flat trajectory with a thin but yet very high kinetic energy round?

is 7mm the king ?
Click to expand...

Bah, all this math and argument when we ALL KNOW the answer...

...Phased plasma rifle in a 40Watt range or sharks with frikin' lazerbeams attached to their heads.
 
The .408 Cheytac is just a scaled-up .308 Winchester. It is 4/3rds the size of a .308W, so you can expect it to produce:

(4/3)^3 = 2.4 times the muzzle energy (because the bullet will be 2.4x as massive, at the same muzzle velocity)

3/4 the wind drift (because the bullet is 4/3 as long as a .308 bullet).

4/3rds the effective range of a .308W (what a .308W can do at 600y, a .408 can do at 800 yards)

It's not a super-high performance round, either wind-drift-wise or flat-shooting-wise. It was designed to simply be a "bigger .308W", and it does that.

And FWIW, the .50BMG is just simply a scaled-up .30-06 (a 5/3rds version). Whatever a .30-06 can do at 600 yards, a .50BMG can do at 1000 yards.

(For fun-in-scaling, put a .222 Rem, a .30-06 and a .50 BMG next to each other....)
 
rnbra-shooter said:
The .408 Cheytac is just a scaled-up .308 Winchester. It is 4/3rds the size of a .308W, so you can expect it to produce:

(4/3)^3 = 2.4 times the muzzle energy (because the bullet will be 2.4x as massive, at the same muzzle velocity)

3/4 the wind drift (because the bullet is 4/3 as long as a .308 bullet).

4/3rds the effective range of a .308W (what a .308W can do at 600y, a .408 can do at 800 yards)

It's not a super-high performance round, either wind-drift-wise or flat-shooting-wise. It was designed to simply be a "bigger .308W", and it does that.

And FWIW, the .50BMG is just simply a scaled-up .30-06 (a 5/3rds version). Whatever a .30-06 can do at 600 yards, a .50BMG can do at 1000 yards.

(For fun-in-scaling, put a .222 Rem, a .30-06 and a .50 BMG next to each other....)
Click to expand...

Wow... i had no idea a 30-06 would produce 6000 lbs at 600 yds.... learn something everyday...
 
rig_pig69 said:
Wow... i had no idea a 30-06 would produce 6000 lbs at 600 yds.... learn something everyday...
Click to expand...

Something is wrong here. The 06 does not produce 6000 lbs at the muzzle in fact it is about 1/2 that.
The 180 gr 308 cal bullet times 4 is 720 which is slightly lighter than the 750 gr Amax bullet which the 50 performs very well with.
Taking the 3100 FTLBs of energy that the 06 generates times 4 is gives you 12400 which is also less than the 50 generates at the muzzle.
Someone lost me with all the math too.
 
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