One of the varibles, when it comes to bullet stabilization, is bullet lenght. As I understand it, the shorter a bullet the better it is stablized within a certain twist rate and velocity, ie. 1x14 twist will stablize a bullet with a lenght of .683" to .669" over 2800'/sec. However it seems to me that it shouldn't be the lenght of the bullet, but the lenght of the bullet in contact with the lands and possibly the ogive design, weight distribution etc. If this is true the new package of 55gr. Nosler Combined Technology bullets wont stabilize in my 22-250AI 1x14 twist barrel since they are .810" (approx) in lenght. Does any one have an explation that makes sense to me?

According to my Lee programs Twist calculator you need a 1-9.5 twist for this bullet. I`m not one to try to explain twists and bullet construction as I don`t realy under stand it anymore then that it`s a lenght, diameter, thing with a bit of variation caused by velocity.
I doubt though with as much difference in twist needed to what you have that your rifle will shoot the Nosler very well.

You are thinking backwards. You don't have to stabilize the bullet in the barrel, you have to stabilize it in the air.

Weight distribution of the bullet is important (if the center of gravity would be ahead of the center of the bullet, it would be inherently stable!), as is the length of the bullet, and the air density.

Since the poster is in SLC, we are talking about 5,000 ft in elevation, which translates into 83% air density. Thus, 17% less twist is needed to stabilize the bullet: your 55 grainers will stabilize just fine! HTH, Dutch.

Just curious Cool, how did you determine the bullets aren't stabalizing? Are they tumbling on the target, etc.? Dutch is right. it's the air & gravity, the bbl. just gets the bullet going in the best condition to meet those variables.
Have you used moly bullets before? Your bbl. needs to be very clean & then you have to shoot a few to "season" the bbl. You rifle may just not like this bullet. Good luck.

Many years ago when I first started reloading little attention was paid, at least by me to bullet lenght. My Ruger #1 pumped out 55gr Nosler solid base bullets in the .27 to .35" range at 100 yds. I made a few bucks taking the neck from beer bottles at 200yds. I never even gave a thought to "stabilizing". Most of the shooting was done at 6000' and above. I don't even know if you can get that bullet any more? I seems to me that a solid base of copper would put the weight foreward on the bullet.
To tell the truth I haven't loaded any of the Nosler Combined Tech. bullets yet. I was just going on the "twist" programs I've seen. I'll try them and see what happens.....
Dutch does this mean I might be able to stabilize a 60gr at between 8-10,000', that's where most of my shooting takes place ??? Thanks everyone

quote:

Originally posted by CoolHunt:
One of the varibles, when it comes to bullet stabilization, is bullet lenght. As I understand it, the shorter a bullet the better it is stablized within a certain twist rate and velocity, ie. 1x14 twist will stablize a bullet with a lenght of .683" to .669" over 2800'/sec. However it seems to me that it shouldn't be the lenght of the bullet, but the lenght of the bullet in contact with the lands and possibly the ogive design, weight distribution etc. If this is true the new package of 55gr. Nosler Combined Technology bullets wont stabilize in my 22-250AI 1x14 twist barrel since they are .810" (approx) in lenght. Does any one have an explation that makes sense to me?

But it isn't true! It is the TOTAL LENGTH of the pojectile that determines how fast it must rotate to fly point-on. The amount of bullet shank that is groove diameter has nothing to do with it, unless this section is so short that it strips!

CoolHunt,
Go here and download the WinLoad V2.12 software. It includes WinGyro and that should answer most of your questions regarding ogive length, bearing surface and boat tail configuration.

Ah Cool, don't be so theoretical. Shoot a few first before you worry about this or that. It always comes down to the actual shooting, doesn't it?

Your right, I'll go back to the way I've always done it. If there is one hole, it's good. I'll worry about the small stuff later. Thanks

quote:

Originally posted by Gerard:
CoolHunt,
Go here and download the WinLoad V2.12 software. It includes WinGyro and that should answer most of your questions regarding ogive length, bearing surface and boat tail configuration.

Couldn't download it. It said "invalid or not supported".

Could you tell me why a 200 grain TSX with an overall length of 1.5" and a contact length of .93" was keyholing when shot out of a 30-06 with a 1 in 11 twist at 2532 fps? The 200 Accubond with an overall length of 1.492" and a bearing surface of .870" did not keyhole with the same load and shot faster at 2581 fps.

Thanks for your help.


Einstein: The definition of insanity is doing the same thing over and over and expecting a different result.

The increase in speed is really of minimal importance. The reason is that the faster speed increases the RPM's, but the increased velocity also increases the "overturning moment", i.e. the tendency of the air resistance to cause tumbling.

As speed increases, the stability does increase, but only very slightly, because the overturning moment increases almost as much.

The slight increase in length, combined with a different shape (no boat tail on the TSX, I would guess: the boat tail on the accubond moved the center of gravity farther forward, comparatively), led to the instability. HTH, Dutch.

Try that link again. I just downloaded it and it worked fine. Might have been a temporary problem.