250gr A Tip in a 308

[steve123]

I don't know about a 45-70, but do the math on a 200+ grain .30 cal at 1000 fps and 1010fps. The math says about 7" of vertical between the two at 500 yards. A .300 BLK is just plain slow, so you have to lob them. It's cool at short range because you lose almost no muzzle energy by the time you get to the target - they just don't slow down. But beyond a couple hundred yards, and you get lots of vertical simply due to muzzle velocity variation. It's just not designed for the task.

Ah, I hadn't done the math and didn't think there was that much vertical at 500Y with 10 fps ES.

My friends must have less than 10 fps ES?? because they can keep centerline-ish at 500M on Rams with blackpowder and those 535's. They have worked hard on their loads and they weight sort the bullets.

 

[steve123]

What's the math for that 250 grain Atip at 2500 fps with 20 fps ES?

 

[rimfiremac]

What's the math for that 250 grain Atip at 2500 fps with 20 fps ES?

You can do it with second order equations, but most folks use an app.

 

[dcali]

What's the math for that 250 grain Atip at 2500 fps with 20 fps ES?

About 6" at 1000 yards. Keep in mind this doesn't account for barrel vibration - it's just the raw ballistics.

FYI, This is one reason I made this bullet comparison calculator- it makes it easier to run side by sides like this:

https://bisonballistics.com/calculators/bullet_comparison

 

[dcali]

Ah, I hadn't done the math and didn't think there was that much vertical at 500Y with 10 fps ES.

My friends must have less than 10 fps ES?? because they can keep centerline-ish at 500M on Rams with blackpowder and those 535's. They have worked hard on their loads and they weight sort the bullets.

I don't know what the ballistics of those big bullets is like - They're going a bit faster than a subsonic 300 BLK at the muzzle, and the bullets are obviously different. You'd have to run the numbers specific to those to see how much vertical to expect.

 

[davidjoe]

I probably don’t have the freshest barrel available for flattering group size tests but I do plan to run some from 600 at some point pretty soon. It’ll be interesting to see velocity at the target versus muzzle, regardless.

 

[mr45man]

What is the time of flight at 1000 yds?

I fired a 5 shot group this morning, going downrange to check after lunch.

 

[XTR]

...do the math on a 200+ grain .30 cal at 1000 fps and 1010fps. The math says about 7" of vertical between the two at 500 yards. ....

I have not run the comparisons on paper myself but it's my understanding that most ballistics calculators tend to have problems with subs. If what I have read is correct the issue it that drag characteristics are very different for super vs sub sonic and the drag models are based on SS flight so are not correct so beyond a couple of hundred yards they are not accurate for subs.

Typically though for most of our supersonic bullets something on the order of 15FPS equals about 5 inches at 1000 based purely on the flight ballistics.

 

[dcali]

I have not run the comparisons on paper myself but it's my understanding that most ballistics calculators tend to have problems with subs. If what I have read is correct the issue it that drag characteristics are very different for super vs sub sonic and the drag models are based on SS flight so are not correct so beyond a couple of hundred yards they are not accurate for subs.

Typically though for most of our supersonic bullets something on the order of 15FPS equals about 5 inches at 1000 based purely on the flight ballistics.

I agree. It's definitely harder to get good data on subsonic drag - nobody ever really cares if the drag curve doesn't match up well there if the supersonic part is good. That could mean that BCs that match well at subsonic speeds might match poorly at supersonic speeds. That said, subsonic drag is *very* low in magnitude, and you should be able to get a pretty good idea of short-ish range trajectories or relative effects.

 

[steve123]

I don't know what the ballistics of those big bullets is like - They're going a bit faster than a subsonic 300 BLK at the muzzle, and the bullets are obviously different. You'd have to run the numbers specific to those to see how much vertical to expect.

Thanks for taking the time to point all this out!

I learned something new.

 

[dcali]

Thanks for taking the time to point all this out!

I learned something new.

There's a lot of weird stuff that happens around the sound barrier. It's fun to play around with a calculator to see how it works. Sometimes it's surprising. A classic example is subsonic rimfire ammo tends to have less wind deflection than super sonic ammo.

 

[jsthntn247]

What about the new Hodgdon ball powder. Supposed to be temp stable and 4350 burn rate. Shouldn’t be as compressed.

 

[WIB3]

Why are you wasting your time and money with a .308 with 250’s. Put them in front of a WSM. Even that is marginal. I once tried 240 Sierras with a WSM. The best velocity I could get using 4350 and RE-23 was 2630. Shot ok but unfortunately not competitive at the 1000 yd game. The bullet is perfect for a larger case, but unfortunately slow burning power is behind the 8 ball. Have a couple thousand 250 sierras which I tried after bonding the core, again shot ok, I the 7-8” range but not exceptional. In my opinion, they need to be able to reach the 2800+ FPS range to have a significant advantage.

 

[WIB3]

You might want to contact Tom J. of VT Bullets and try some of his 207gr Bullets. They might turn some heads. They might be what you are looking for and they will have the ability to be shot out of your .308

 

[WIB3]

He has a reputation for producing some of the most accurate 6mm Bullets in the world. His Bullets hold many world records. Don’t be swayed by claimed high BC numbers, in all practically, hard work at the reloading bench is worth more.

 

[APGE]

Why are you wasting your time and money with a .308 with 250’s. Put them in front of a WSM

Because the application is FTR, where a 308 is permitted and and 300wsm is not

In my opinion, they need to be able to reach the 2800+ FPS range to have a significant advantage.

The design of the 240smk is generation's behind that of the 250 ATIP. The 250 ATIP, as stated earlier in this thread, can travel at 2400fps and have a significant advantage over other ftr applications.

 

[Down South]

You might want to contact Tom J. of VT Bullets and try some of his 207gr Bullets. They might turn some heads. They might be what you are looking for and they will have the ability to be shot out of your .308

Peter Johns shoots them in one of his FTR rifles. He's got them shooting very well.

 

[davidjoe]

Why are you wasting your time and money with a .308 with 250’s. Put them in front of a WSM. Even that is marginal. I once tried 240 Sierras with a WSM. The best velocity I could get using 4350 and RE-23 was 2630. Shot ok but unfortunately not competitive at the 1000 yd game. The bullet is perfect for a larger case, but unfortunately slow burning power is behind the 8 ball. Have a couple thousand 250 sierras which I tried after bonding the core, again shot ok, I the 7-8” range but not exceptional. In my opinion, they need to be able to reach the 2800+ FPS range to have a significant advantage.

If it worked, it would be a first, and the only example, for a “heaviest” bullet in any caliber to gain traction in F-Class. The 90’s don’t overrun the 80’s. Even in Open, the heaviest bullets aren’t the accepted choice for any cartridge run.

Not only are the heaviest bullets hard pressed to produce a net advantage, but so are the largest calibers. At and inside the 1,000 yard max we shoot, we simply hit a hard ceiling of diminishing returns. (Although I’ll write that observation about the field, my own favorite bullet to shoot remains the 195, the heavy 7.)

F-Open permits .35 caliber and I’ve made and shot weight limit .338 Lapua magnums with tolerable recoil, but 1,000 yards is simply too close to see a wind drift advantage (awaiting the next generation bullet; the Scenar is incredibly consistent but lacks BC).

So it’s not just a case of the A-Tip against the 200-20x, rather it’s Hornady against the entire history of heaviest bullet choice in F-class. If it works, that would be a LOT of credit due them.

 

[Ned Ludd]

If this experiment with the 250 A-Tips is successful, I predict that within 10 to 15 years, all the top F-TR shooters will be using bullets that are more like arrows or darts; i.e. solid .308 diameter projectiles, of at least 8" to 10" long.

 

[XTR]

If this experiment with the 250 A-Tips is successful, I predict that within 10 to 15 years, all the top F-TR shooters will be using bullets that are more like arrows or darts; i.e. solid .308 diameter projectiles, of at least 8" to 10" long.

If I could just get the guys at ARL to work with me .....