stablizing vs shape vs material ??
 

I've explored a similar question a couple of times ,but I guess I'm not asking the right question.
I've looked up twist rates and used the Greenhill formula and with all that I've found that my slow 1-12 308 should stablize the 180rn bullets as well or better than the longer 150spbt and that either of my 1-10 3006's should handle nicely a similar 200 rn or 180spbt lastly my 1-8.5 3006' should get it done with a bullet much longer than any of those and upwards of 230 grns pointed over 250 round nosed.

If I stick with a single bullet profile let's randomly a 165 grain TSX with its high .400 bc an identical "cheap"cup and core should tip in at 175-180 and both should shoot equally well in all 4 rifles. A cast bullet should hit 195 or so and should shoot just as well even if it has to be shot slower. But the cast bullet throws a wrench in the works or so I've been told several times.

The round nose profile works out most likely weighing in from 180-210 in all forms. Again they should shoot well.

What if I go full wad cutter matching the 1.15 " length of the above that copper solid is going to hit 200 easy with the cast tipping in around 225. In pistols wadcutters always shoot well so the same should hold true if you can take the heavy bullet beating in rifles.

Why does bullet stability and shootablity change so much with a change in bullet material . By proportion the all copper bullet should have the same balance and flight charactoristics as an identical cast bullet and in scale the identically shaped cup and core will be just slightly nose heavy. Based on that the cup and core ought to be out shot by either of the solid bullets,right?

As I write I see that maybe it has more to do with the relationship of twist rates to bullet density than having to do with shape .

Humpf! Great now I have more to chew on and more questions to seek out.

When talking about twist rates the length of the bullet is what you need to be concerned with more than the weight. One would just figure the heavier the bullet the longer it is and that isn't always true. Bergers web site has a guide for optimum twist rates with their bullets.

http://www.bergerbullets.com/Product...20Bullets.html

Because copper weighs less than lead and therefore a 150 grain all copper bullet is the same length (aproximately) as many 165 or 180 grain lead core bullets.
You need to know the length of the bullet and the velocity at which it will be fired, and nothing else, to calculate what twist rate you need for a given bullet.

FORMULAS and PROFESSORs and TEXTBOOKS...sure, they have the right ideas but I've found that there's nothing other than letting them fly in YOUR rifle, with YOUR TECHNIQUES and loads that will tell the story, nothing better than good old benchtime, NOTHING!

Let me try again ?

4 identical bullets out of a CNC machine. 1 ea.cup and core,bronze,copper,wheel weight.
All fired at the same fps in 1 gun all should have the same target performance ,same group similar impact point. In point if they are wad cutters or the like they should all clump together. Pointy bullets don't/won't do that. The bronze hit hi ,copper goes pretty much where it feels like,cup and cores generally go where pointed,and lead often tumble & pattern. Why? It can't be CG as all of these are of the same shape and dispersion of weight even though the weight is differant its in the same place. Bbl friction is only differing on the lead and copper bullet but should be negated buy keeping the same fps.

It the hardness of the material used. Wheel weight even being harder than pure lead is not going to grip the rifling as well as copper will. So there is a limited slip factor envolved. But a casted hard lead bullet made from wheel weight should out preform most pure lead bullets. Has never played with bronze so I have no comparison vs copper jacketed bullets. In pistol shooting past 25yds I've found copper to be the most reliable and consistant.

Its not a fair comparison. Lead will not be able to get the spin the others will because of its surface tension.

Mine won't:mad:

But shoots great 32gr.:lmao:

I might be in a little over my head but wouldnt the materials with similar sectional density shoot similar groups then? Is there any research about this subject?

Thought about it. But I have killed a bunch of critters with the 32gr nosler and it held together better than 32gr hornady. Seems the nosler had no problems killing anything up to the fox size.

I am kicking out 4100fps now with 32gr. I would like to have higher BC, and maybe more punch for a coyote, but still seems I loose all steam at 600 yards with the 204 no matter which bullet.

Wind does raise havoc on this bullet. More than the bullistic calcs say. I am lucky to be getting 2MOA at 500 yards. Clean missed a fox last year at 420. But pull off sub0.5MOA at 100 and even 200 yards. Every time I take it out for long range groundhogs, winds been over 15MPH.

Have you guys used that a-max bullet any?

No doubt. I don't own a 22-250. But plan to.

You know the more I think about it I've never had a single rifle that ever liked any of the A-Max bullets in any caliber...maybe it's just me but they've never shot well in anything of mine...

I meant to say dimentionally identical. Yes I am well aware that the bronze (GMX) will be much lighter than a wheel weight bullet(cast) . If they all leave the muzzle at (randomly picked)1900fps then they ought to fly the same. They will have the same bc and same flight time as such the mathmaticaly same drop. I'm only concerned with the external balistics not the internal. I'm also aware of the friction issues charge weights,powder choices etc. What about what happens in the last inch of the bbl and the 1st 50yrds out of the bbl that makes shooting a full spire/spitzer/flat based GMX/TSX shaped so flakey that moulds are generally not available and discouraged by all but pro-shooters. Why do they work in the monster500grn 1000yrd 45s but not in the dinky 180grn 200yrd 308 proficiency gun?

No they won't. The heavier bullets of the same length and shape will have a higher sectional density and higher ballistic coefficient and if launched at the same speed will have less time in flight due to the higher BC.

You must be concerned with what happens inside the barrel before you can be concerned with what happens outside the barrel. What happens inside the barrel effects what happens outside the barrel.

Still baffled how do they get tracers ball explosive and armor peircing fed through the same 50 bmg to hit inside 24" at 500yards and not collide in flight when launched at 8 rounds per second or more often shooting any 2 or all of the above if I'm totally wrong in my theory?

Ok so I checked out a BC calculater sure enough based on a 130 copper 150 cup n core and a 160 wheel weight the BC changes .299,.345,.367 ,not a point I had considered.I got out my shooter program with a 100yrd 0 and 1800fps in deference to the wheel weight bullet it amounts to 64 fps and .6 inches of drop at 200 yards.

How come a cast bullet shaped like a barns triple shock wheel weight clone is said to be too hard to shoot good but the copper original shoots just spiffy and a very similar cup n core shoots just spiffy ?

Why is that such an amazing feat?

Take a 30-06. A 110,165, and 180 grain will hit within 9" despite having 800 fps difference in starting velocity.

If you add in a 220 grain with a big ugly round nose, you change things, but 50 bmg bullets are closer in weight and shape than that.

As for collisions, the 50 bmg round are probably within 100 grains of each other, and have similar shapes. The deferences in velocity are compensated for by BC. So why would the come close to hitting each other, for one. The round behind would likely not catch up.

For two, what are the odds of them hitting even if they do pass one another up. You can't shoot a group at 500 yards with bullet holes touching with different weight bullets when you're not firing full auto.

A cast bullet is hard, but it is nowhere near the hardness of copper.

So my 3 bullets don't care how fast they go nor what the twist rate is as long as the lands get a bite and the bullit gets out of the bbl with enough spin to get stable?

Shape has no real bearing on flight untill way after a small caliber
cast bullet is done flying.

So if the bullet length jives with twist rate and shape doesn't matter an "X"(TSX,GMX)shaped bullet gaschecked or plain based fitted properly with old fashioned powders ,as opposed to modern, should deliver equal TO target performance to the cup and core or copper cousins of the same BC and SD ? Please note to target not target performance.

All three matter. Shape matters. Sleeker designs cut through the air better. The problem is different shapes are better for different velocities. A relatively blunt roundnose .22 lr is better for the velocities typical of a .22. A long sleek Amax is better for high velocity. Two bullets of the same size and shape but of different weight have the same air resistance.

That is why weight matters. The heavier bullet will hold velocity longer for what should be obvious reasons.

Twist matters a little bit, but not in this case. The length of the bullet and to a small extent the velocity determines the twist needed to stabilize it. Three bullets of the same shape and size but different weight will all require the same twist. The light bullet may destabilize first but that is kinda irrelevant.

There are way too many variables to tell you what would happen in your case. The light bullet would have the fastest muzzle velocity, but the powder wouldn't burn as well if the same powder charge was used. It would shed the most velocity on the way to the target and the wind drift would be the highest.

The heavy bullet would use the powder most efficiently, and have the lowest muzzle velocity. Depending on how far the target is, it could have the most drop or the least.

This has sorta left the track of my op but also brought out good points. My original quest was to find a better "why"for the small cal.,.30,8mm in my case,lack of high BC spire pointed type cast bullets or moulds. To date I've had "the tips get deformed too easy""they're too hard to get to shoot well/consistantly"and my favorite"you're an idiot if you're punching paper with TSX's". This thread has reinforced my belief that it can be done and that it will be sucessful enough for just about any caster shooter to do well.
My bullet as of now tips in at 200 grains has a .11 meplat and a calculated BC of .476 . So far hitting 1800 in any of the rifles hasn't happened due mostly ,at this point ,to lube failure. I need 1725 to get the minimum legal energy limit.

As I said, in the lower velocity ranges, a round nosed bullet can actually be more aerodynamic. I think that is at the speed of sound or below. You may be above that range, at 1700 fps.

However, at that velocity you get rainbow trajectories anyway so why do you care about bc?

You want help with this go to the cast boolits forum. They know their stuff.

Have found a great deal of info and inspiration there. However this senerio is outside of most of the guidelines.

Seeking the BCs will allow me to actually shoot quite flat ,comparitively. I have the insight to know this bullit will half the effective no hold over range. This is really more about 200 yard competency as I flat threw away my 1 shot last October.