Come on bullet makers!!!

[elkaholic]

I hope you don't mind, I'm holding you to that! RIGHT NOW!

I am currently shooting a 1:8 twist 300 RUM:

It will push 260's to the 2850 fps range easily. With a BC that beats the 300 SMK, that's plenty fast.

I can test for BC, I can do penetration tests in gel.... Just make the **** things and send them my way!

PM me with a phone # and we will talk.......Rich

 

[elkaholic]

Increasing velocity only has a very small effect on increasing gyroscopic stability. The primary factor effecting a bullets ability to be stabilized is its length.

The berger 210vld would have a stability factor of around 1.4xx from the 11 twist barrel and you dont want to make it any less than this or you will run into stability problems when shooting in cold conditions at low altitudes. Bullet makers must have sufficient safety margin when quoting required twists for conditions like this.

The new hornady 225gr bullet will be about as good as you will get from a 1:10twist barrel, and its only a small improvement from the 210grainers... if you want more BC than this in 30cal, you have no choice but to design a significantly longer bullet which means you have to goto a faster twist barrel.
BC is not just gained purely from increasing mass alone, its only half the story. The rest of the equation comes from the drag of the bullet which is governed by its shape. Aerodynamically efficient shapes with low drag, are very long pointy shapes and due to their volume, a pointier bullet with a longer secant nose will be lighter for the same length. so in reducing aerodynamic drag your also reducing its weight for the same length and you end up chasing your tail with regard to BC... so you very quickly run out of room for improvement which is exactly what has happened in 30cal due to the common 1:10twist barrel.

So designing a bullet for a significantly higher BC than whats already available in 30cal, just isnt feasable when your limited by a 1:10twist rate. Sure berger could design a slightly heavier bullet of 225-230grains and specify a 1:10 minimum... but dont expect the BC to be much better than their 210gr nad youll be running them a bit slower so youll loose most of what you gained anyway... go down to a 1:9 or 1:8 twist and then we can push the designs to much higher BC`s well above 0.7... same goes for alot of calibers tho... but whos gonna make bullets for barrels that dont exist, or are only able to be stabilized above 7000ft altitude and 60deg temps?

Groper is correct!......Rich

 

[elkaholic]

Just for info purposes: My 260 grain SXR fired at 2900' would still have 1000 foot lbs. at just short of 1 mile and would expand at very nearly that far. The 210 Berger fired at 3300' would have 1000 ft. lbs. at about 1380 yards and would maybe expand at about 930 yards......Rich

 

[X3MHunter]

Berger is coming out with a 30 caliber Hybrid.

 

[Jon A]

My 260 grain SXR fired at 2900' would still have 1000 foot lbs. at just short of 1 mile and would expand at very nearly that far.

Now that's what I'm talkin' about! PM on the way.

 

[3006savage]

My understanding is that the preliminary BC of the 225 grain hornady HPBT is .711. If that is true it is a pretty significant step up from the .64 or so BC of the 208/210 grain offerings out there and would seem to be more than a worth while gain.

I am getting that info from another Forums site so take it with a grain of salt is guess.

 

[RockZ]

Looks like Jon beat me to it.
Let us know how it goes

 

[load]

Increasing velocity only has a very small effect on increasing gyroscopic stability. The primary factor effecting a bullets ability to be stabilized is its length.

actually velocity has alot to do with it .gun)
1/10 produces about 168000 rpm @ 3000 fps and 145500 rpm at 2600

1/9 produces 162000 rpm at 2600 fps

@ 2600 fps the 1/9 produces less gyroscopic effect than a 1/10 does at 3000 fps.

speed can make up for twist as long as the bullet can handle the velocity

 

[load]

My understanding is that the preliminary BC of the 225 grain hornady HPBT is .711. If that is true it is a pretty significant step up from the .64 or so BC of the 208/210 grain offerings out there and would seem to be more than a worth while gain.

I am getting that info from another Forums site so take it with a grain of salt is guess.

the # I heard was .67 however if it is .711 WOW! i'll take it!gun)

 

[load]

Just for info purposes: My 260 grain SXR fired at 2900' would still have 1000 foot lbs. at just short of 1 mile and would expand at very nearly that far. The 210 Berger fired at 3300' would have 1000 ft. lbs. at about 1380 yards and would maybe expand at about 930 yards......Rich

I Really want to see the out come of this

 

[Gary Morgan]

I received an e-mail from Hornady that said that Midway USE would the 225 Hornady in stock as of March 1st, 2011.

 

[load]

gun)

 

[Michael Eichele]

actually velocity has alot to do with it .gun)
1/10 produces about 168000 rpm @ 3000 fps and 145500 rpm at 2600

1/9 produces 162000 rpm at 2600 fps

@ 2600 fps the 1/9 produces less gyroscopic effect than a 1/10 does at 3000 fps.

speed can make up for twist as long as the bullet can handle the velocity

Speed can help yes but not as much as you might think. Equal RPM for euqal RPM does not make for equal stability factors. It is true yes that sometimes when a bullet/twist combo is on the line of stability/instability for one caliber it can be suitable for a faster version such as comparing a 308 to a 30-378 but we are still talking about minor stability differences even for 1000'/sec difference you may see a stability factor of 0.10 - 0.12 change. The 308 load was 1.03 and the 30-378 (1000'/sec faster) is only 1.14. This is the difference between the ragged line and definate stability but it is still a low Sg.

A bullet that is 1.72" long, .338 in diameter, 300 grains, and is jacketed lead fired in a 13x barrel at 2600 FPS offers a 1.1 stability factor. Bump it up to 3000 FPS and the factor only goes up to 1.16 even though the RPM is 166155 up from 144000.

Using a 12x barrel you find 180000 and 156000 RPM respectively yet the Sg at 2600 FPS is 1.32 even though the RPM's of the 2600' load in the 12 twist barrel is between both velocity ranges for the 13 twist barrel.

Make it a 14.5 twist and launch them at 3400' and see that the RPM's are 168830 yet the Sg is .99 which is clearly unstable even though the RPMs are comparable to the above examples.

When it comes to stability in rifles, RPM's alone are not a reliable way to determine stability.

M

 

[desertbull]

What is the reason we cannot get a bonded (Accubond, Interbond) or ballistic tip (Nosler BT, Scirrocco) style bullet in the high BC design such as the Bergers and Amax?

Seems like they would fly off the shelf if they were available.