Help with stabilizatoin issue. where do I go from here?

[Whiterabbit]

OK, so I have a bullet I'm trying to get to shoot well, it's just not cooperating. I have ZERO loads for this bullet that work.

I'm using H110 which for my gun pretty much represents the max speeds I can get for most given bullets. The bullet is moving from 1700 (slowest) to 1900+ (fastest) fps (based on documentation, not epirical testing)

SO! I have a 300 grain bullet in a factory load that is .8 inches long that shoots GREAT. Actually, I've never shot so well as with that round.

The bullet I'm experimenting with is 340 grains and .92 inches long. Pretty darn close, but "slow" (3% down w/H110) vs fast, I always get at least one bullet per cylinder that tumbles:

Picture of tumbling bullet

As you can see the accuracy is terrible too.

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So the bullet is rated to 2000 fps, I'm not maxing out the BULLET. The light loads didn;t work so I kept pushing it and pushing it and pushing it, this round is the first time I've actually seen a pressure sign, there's still tumbling bullets @ max.

#1: if fast doesn't stabilize, slow won't either, right? no point in trying further reducing the load (with or without other powders) is there? Or is there? Is it possible to de-stabilize the bullet by pushing it too fast?

#2: any other ideas how to make the bullet work?

[G-forceJunkie]

What gun? What twist rate? What cartridge are we talking about?

[Sub95]

what is the twist rate.

The longer bullet might not like the twist rate.

[Whiterabbit]

1 in 16. what do you guys plan to do with the data? the stability calculators do not generate useful data in this case.

[Sub95]

what is the oal of the 300 grain bullet? and what is the 340gr oal?

[Whiterabbit]

.8 and.92 inches, respectively.

The .8" bullet is moving at 1750 fps as per the factory. The .92" bullet is moving from 1700 to 1900+ fps depending on the load I was testing, based on documentation.

[Sub95]

i mean a loaded case/bullet oal

and are this both lead bullets?.

[Whiterabbit]

I can give all sorts of details if needed. Can you go into some detail about what the cartridge overall length has to do with bullet stabilization? Also what the difference is between lead, jacketed, and copper that DOES NOT have to do with length.

Cause the internet tells me (and the internet is always right, right??) that even bullet weight is not really critical to stabilization, compared to length. That bullet length is the main dictator of stabilization.

But really, if I start providing all sorts of numbers, presumably it's gonna go into an equation of some sort, right? What's the equation? If it's qualitative stuff, all the numbers don't mean so much, right?

[Whiterabbit]

In short, what would you do with the numbers you are asking for? Helps me learn, too.

[Sub95]

lead vs copper jacket vs bt ect has a role in stabilization, loaded oal has a role in stabilization.

trying to see if the two loaded rounds are different other then power charge and weight.

if you can get the 300gr bullet to not key hole, what is the difference bettween the two other then weight. you have to find this out before you can go on.

[G-forceJunkie]

I can give all sorts of details if needed.

Then how about answering the questions already posted to you? Why are you trying to make this hard and be vague?

[Whiterabbit]

I tried the stabilization calculator here:

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

To see if that would give me a clue (before I posted here) but no dice. The numbers are all very high. Miller index of 9 for factory and 7.x for my reloads. Nowhere close to 1.5. Basically tells me that the stability calculation is not the only factor in what makes a bullet tumble.

So if it's not just stability calculations, what else can cause a bullet to start tumbling? A specific example would be helpful to try to draw relateable conclusions.

[Whiterabbit]

I don't but have seen references to it online. is it a website program or something, like the stability calculator I linked to? It's a download?

The goal is to get these 340's to shoot accurately for paper punching. They are lead, so CA won't really let me use them anywhere else, anyways. So energy isn't important, terminal performance, etc etc etc, none of that matters. Just needs to shoot accurate (preferably at all distances from 10 yards to 100 yards)

Not sure what you are referring to about the pressure curve, but is the implication that the burn rate of the powder might not be appropriate for the bullet and load? I thought of that, but I'm not sure how I can prove that. H110 is right in between trailboss and leverevolution, which are used in rounds that seem to work well using other bullets in other loads, but I don't know what powder is used in the 300 grain factory stuff.

In short, faster stuff *can* work well, and slower stuff *can* work well, but different bullets, different speeds, etc. So not sure if the relationship can be made.

[jimmykan]

Probably a 45 Colt or 45-70 Government. I want to say 45 Colt from the 16" twist rate, but 1700 fps is very fast for a 300-340 grain cast bullet in 45 Colt, even from a 20" rifle barrel.

[sonnyt650]

...
.8 inches long that shoots GREAT

.92 inches long... at least one bullet per cylinder that tumbles

... #1: if fast doesn't stabilize, slow won't either, right?

According to my Hornady manual, a bullet where center of mass isn't consistent around the bullet center will throw rounds wide just because of the spin. Increase the rate of spin (faster loads or higher twist rate) and the problem will be magnified. However I don't know why that would cause one of the rounds to just go sideways like that where the faster it spins the better the gyroscopic effect and so bad bullets should just cut perfect holes away from the POA. Slower isn't going to be any better would be my guess.

Maybe there's an oversimplification though with the really long bullets throwing either the head or tail of the bullet off more than the rest? Yeah give slower a try.