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30 cal turned heads

 
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  #8  
Old 05-01-2009, 10:15 PM
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Re: 30 cal turned heads

Copper has a specifec gravity factor of 8.89. Jacketed lead averages 10.7. The higher the SG, the higher the BC. The lower the SG, the lower the BC. Equal shape for equal shape jacketed lead wins. Same weight for weight, things will be similar in BC despite the longer length of all copper.

Make sense?
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Old 05-02-2009, 01:03 AM
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Re: 30 cal turned heads

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Originally Posted by Michael Eichele View Post
Copper has a specifec gravity factor of 8.89. Jacketed lead averages 10.7. The higher the SG, the higher the BC. The lower the SG, the lower the BC. Equal shape for equal shape jacketed lead wins. Same weight for weight, things will be similar in BC despite the longer length of all copper.

Make sense?
Makes sense. I knew the higher density material would make a higher bc. I suppose we can't figure out the the difference between the imaginary copper bullet and the 240 SMK as long as the copper bullet is imaginary. I would love to know the difference in bc between the the identical shapes and how much weight difference there would be, then translate that into relative velocities for each bullet. Then calculate drop and drift.

So, someone needs to get busy on the lathe.

Steve
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  #10  
Old 05-02-2009, 02:41 AM
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Re: 30 cal turned heads

There is always going to be a trade off between mass, velocity and BC. It would stand to reason that a material with higher density would have a higher BC, all else being equal. On the other hand... higher mass means lower velocity. Usually though, the hevier and higher BC bullets will out distance the lighter faster bullets in the same cartridge.

Then comes the question of application... paper punching or animal killing... and there are a lot of variables in that question.

Generally speaking, my first priority in choosing a "hunting" bullet is accuracy (as long as it is IMO, a reliable killer). Next is terminal perfomance, i.e. monometal vs bonded vs non bonded, etc. Next is BC.

So in some cases I might choose one bullet at a particular range and another at another range.

Now when it comes to a bullet like the 300 SMK, that has all that mass, with BC to boot... it's hard to beat. But when we're looking at a 180 bullet in 7mm or 308, the trade offs become more interesting.

Wouldn't it be boring without all the variables?
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  #11  
Old 05-02-2009, 03:54 AM
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Re: 30 cal turned heads

ok i get the picture. But this brings up a new idea you said tungsten would give it more weight there for more bc. What if I made it with a tungsten insert what then.
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Old 05-03-2009, 05:04 AM
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Re: 30 cal turned heads

Quote:
Originally Posted by Michael Eichele View Post
Copper has a specifec gravity factor of 8.89. Jacketed lead averages 10.7. The higher the SG, the higher the BC. The lower the SG, the lower the BC. Equal shape for equal shape jacketed lead wins. Same weight for weight, things will be similar in BC despite the longer length of all copper.

Make sense?
Did some loading yesterday to go out and do a little playing at distance. While loading saw this;

180g Nosler Ballistic Tip B.C.= .507

180g Nosler E-Tip B.C.= .523

Michael, does this go along with what you are saying, or not? I know that last year I chose to use the E-Tip over the 200g AB because the increased velocity of the 180g E-tip out performed the 200g AB out as far as I could shoot. I would have to run the #s again but I think about a 1000 yards.

Not looking for a dispute, looking for knowledge.

Steve
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  #13  
Old 05-03-2009, 01:17 PM
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Re: 30 cal turned heads

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Originally Posted by qqqq33 View Post
ok experts why hasnt anyone just turned a longer monometal bullit for the 30 cal. Wouldnt that give it a higher bc. please give pros and cons and what to becareful of. I have the means to turn my own. was thinking of using a 338 lapua turned down to 30 cal
Lost River Ballistics (now out of business) used to make a 220 grain 30 caliber machined copper alloy (looks like brass) bullets with a G1 BC of 0.930. That was one of their J40 series. I've never seen a coment of anyone who's found them to shoot accurately, thoough no one argued about the high BC. Disucssions of why they don't shoot accurately just seem to be mostly speculation. They don't have engraving bands like the more succesfu Lehigh solids. The Barns 50's don't have engraving bands and they shoot well. Perhaps they''re just to long to stabilize well regardless of twist. Perhaps the tests were done at short range (under a mile) where the incredible low drag doens't offer a particular advantate.

I built a 30" x 9" twist 300 RUM Rem 700 with the intention of shooting them but in setting up the rifle I found it shot 210 moly Bergers very well to over a mile. The Bergers are much less expensive. I still have several boxes of the LRB 220's waiting for a reason to try shooting them.
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  #14  
Old 05-03-2009, 02:08 PM
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Re: 30 cal turned heads

Quote:
Originally Posted by qqqq33 View Post
ok i get the picture. But this brings up a new idea you said tungsten would give it more weight there for more bc. What if I made it with a tungsten insert what then.
Barnes has sort of done this. They put tungsten into the aft partof the bullet. It is a more dense bulletl and very spendy. They are still developing the line.
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