I have a question related to WFN type bullets and stability and CoG.

[C. Latch]

I'll try to condense this down into a handful of thoughts:

Last year I had a 300-grain .400" nose .452 mold (76% meplat) made for my .45 Colt.

I like the mold, I have a couple of loads with it that show promise, but with a 76% meplat, the bullet needs a fair bit of velocity for stability; I have found that below 1100' MV stability falls off past 75 yards or less.

I am considering the possibility of having this mold hollow-pointed, in order to make the bullet lighter. My reasoning is that I have more than enough weight to shoot through any whitetail, and a HP conversion would allow me to shift the Center of Gravity rearward, while reducing bullet weight (and recoil) a bit to boot. Even with a large HP and a soft alloy, this bullet should give more than sufficient penetration for the sort of shots I'm likely to take on whitetails, and could always be used with flat pins to continue to cast regular flat-points.

Is there a way to guesstimate the effects of this HP conversion (let's say a tapered pin that takes 15 to 25 grains out of the nose) on stability?

I'm thinking a HP conversion might be:

1) more effective on light game
2) easier to drive to needed velocity (for stability) with less recoil
3) easier to stabilize at a lower velocity.

Also, a HP conversion would make powder-coating this bullet dirt-simple, but that is a secondary consideration.

I'm mainly asking about the stability aspect here. Any help?

[popper]

From the stability equation, it's twist, fps & length not weight that factors in. Arrows are made stable by adding weight to the nose. HPing will change none of those.

[C. Latch]

From the stability equation, it's twist, fps & length not weight that factors in. Arrows are made stable by adding weight to the nose. HPing will change none of those.

You're using a drag-stabilized example to argue a spin-stabilized point. It doesn't work that way. I know, based on physics, that bullets (or any other spin-stabilized projectile) can benefit, in terms of long-range stability, from having their CoG moved rearwards; this is a large part of the reasoning behind plastic-tipped or hollow-pointed match bullets. Drag-stabilized projectiles, such as arrows, are the opposite.

The question, though, is how much those principles will impact this particular application.

[Southpaw 72]

I had the same problem with a mold I designed for a 250gr boolit for my 41mag. It was a bore riding design with an 80% meplat. Pushed it up to 1300fps to get it to stabilize and even then accuracy wasn't that great. Sent the mold down the road and designed another one. This time I got rid of the bore ride section and reduced the meplat to 77%. Pushed to the same velocity it is much more accurate than the previous design. It's made me rethink bullet design. You're doing the same thing I did, just going about a different way. I say go for it. It'll be interesting to see the results.

[C. Latch]

I had the same problem with a mold I designed for a 250gr boolit for my 41mag. It was a bore riding design with an 80% meplat. Pushed it up to 1300fps to get it to stabilize and even then accuracy wasn't that great. Sent the mold down the road and designed another one. This time I got rid of the bore ride section and reduced the meplat to 77%. Pushed to the same velocity it is much more accurate than the previous design. It's made me rethink bullet design. You're doing the same thing I did, just going about a different way. I say go for it. It'll be interesting to see the results.
Yep, sounds like we're on the same road. I started with the Lee 452-300-rf and with it's 80% (or more) meplat, accuracy fell apart quickly past 50 yards with 1200' MV. Dropping to a 76% meplat has helped considerably; better accuracy at longer ranges with less velocity needed, but I'm not where I want to be yet.

[Changeling]

In my opinion the large meplat sets up a considerable disturbance to the bullet and makes it fall to a velocity where it becomes unstable. If the meplat size is reduced "or" the velocity is increased there is a sustained stabilization factor untill one of the 2 factors fail in the equation. Suspically it seems to be the meplat size. Witch has to also be related to bullet length. (Example would be wadcutters)
For some reason when the meplat diameter, length of the bullet for caliber reach some particular velocity this phenominum slows way down and one has a truly long range stabilized bullet.
This is undoubteably what Elmer Keith found with his designs, since he found complete stabilization out to very long ranges. The meplats on his bullets were rather small when looking at what is considered a wide meplat today witch I believe has gotten totally out of hand for the average bullet. However as someone said above, bullet length controls stabilization. NOT exactly true in all cases.