stablizing vs shape vs material ??
03-08-2010, 12:38 PM
#1
Typical Buck
Thread Starter
Join Date: Mar 2007
Location: Wide open Nevada
Posts: 515
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.
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.
03-08-2010, 04:13 PM
#2
Fork Horn
Join Date: Jan 2008
Posts: 240
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
http://www.bergerbullets.com/Product...20Bullets.html
03-08-2010, 05:36 PM
#3
Boone & Crockett
Join Date: Feb 2003
Posts: 10,679
Why does bullet stability and shootablity change so much with a change in bullet material .
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 .
03-09-2010, 03:27 AM
#4
Fork Horn
Join Date: Mar 2003
Posts: 159
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!
03-09-2010, 07:23 AM
#5
Typical Buck
Thread Starter
Join Date: Mar 2007
Location: Wide open Nevada
Posts: 515
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.
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.
03-09-2010, 07:50 AM
#6
Typical Buck
Join Date: May 2009
Location: Colorado
Posts: 797
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.
03-09-2010, 09:28 AM
#7
Guest
Posts: n/a
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.
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.
03-09-2010, 02:21 PM
#10
Guest
Posts: n/a