Difference in bc between lead and monometal bullets?

[benchracer]

Attached is a photo containing several 375 bullets. The two bullets furthest right are the Cutting Edge 300 MTH and the Sierra 350 Matchking. They are very close in length and generally appear as though they would have a very similar form factor.

Based on the Litz data for the 350 SMK (see attached screenshot), the average G7 bc is .380 (.741 G1). Assuming the same form factor, the CE 300 MTH should have a lower bc because it is made of less dense material. CE lists the G1 bc for this bullet @ .750, which I believe to be high (based on Litz's data for the 350 SMK).

I looked up the formula for bc and found this:

BC = Sectional Density (SD)/ Form Factor (i)

SD = Projectile Mass in grains (M)/7000 * the square of the Bullet Diameter in Inches


When I plugged in the data, I ended up with a calculated G7 bc for the CE 300 MTH of .325, which corresponds roughly to a .634 G1.

Did I calculate this correctly? Do these figures seem like a reasonable estimate?

 

[7mmShooter]

Litz came up with a .331 G7 for the 300 MTH, so your calculations are close. As far as the rest of the questions, I'll leave that to the more experienced members

 

[benchracer]

Litz came up with a .331 G7 for the 300 MTH, so your calculations are close. As far as the rest of the questions, I'll leave that to the more experienced members

That is VERY useful information. Thank you!

 

[Mikecr]

Where did you get your form factor (i), and at what velocity?

 

[benchracer]

Where did you get your form factor (i), and at what velocity?

Check out the screen shot of Litz data for the 350 SMK. As I stated, I used the same form factor based on the similarity between the two bullets.

 

[WildRose]

If you take bullets of identical diameter, length and shape one being a monometal and the other being a traditional lead core bullet on average the mono will weigh about 10-15% less depending on the alloy used due to the much higher density of lead.

This is a rough figure because there are lots of factors that come into play such as how thick the jacket of the lead core bullet is etc.

As for the math your figures look to be awfully close.

Barnes tried working around this with their MRX Bullet (I think that's what they called it) by using a tungsten core but for whatever reason those bullets tended not to be very accurate or consistent.

I'm glad that more and more manufacturers are getting into the non toxic market because nothing drives innovation like competition. Just look at how far we've come in just the last 20 years with respect to the long range bullet market as a great example.

 

[benchracer]

If you take bullets of identical diameter, length and shape one being a monometal and the other being a traditional lead core bullet on average the mono will weigh about 10-15% less depending on the alloy used due to the much higher density of lead.

As for the math your figures look to be awfully close.

I'm glad that more and more manufacturers are getting into the non toxic market because nothing drives innovation like competition. Just look at how far we've come in just the last 20 years with respect to the long range bullet market as a great example.

It's funny you mention the 10-15% figure. Based on weight alone, the CE bullet is 85.7% as dense as the SMK. Its bc also tracks that figure.

I agree that it is a good thing that more manufacturers are making non-lead bullets. Overall, just in the last decade, we have all benefited from innovations in bullets and powders. With wider availability of higher performance non-lead bullets, and with improved understanding of bullet flight at ELR, it is becoming increasing clear that tighter twists are needed to support these innovations. I strongly believe that the next big push from the shooting community needs to involve changes to industry standard twist rates for each caliber.

 

[WildRose]

It's funny you mention the 10-15% figure. Based on weight alone, the CE bullet is 85.7% as dense as the SMK. Its bc also tracks that figure.

I agree that it is a good thing that more manufacturers are making non-lead bullets. Overall, just in the last decade, we have all benefited from innovations in bullets and powders. With wider availability of higher performance non-lead bullets, and with improved understanding of bullet flight at ELR, it is becoming increasing clear that tighter twists are needed to support these innovations. I strongly believe that the next big push from the shooting community needs to involve changes to industry standard twist rates for each caliber.

I agree and that is something I posed a while back in another thread.

Remington in particular needs to be much more responsive to a better educated class of shooters who are quite capable of putting a bullet where it needs to be at two or three times the range that hunters have generally considered to be reasonable for the last hundred years. A great example is my 700 VSSFII with a 1:12 twist that basically limits me to 50-55gr bullets from a .220 swift. The small AR manufacturers conversely figured out a decade ago that the .223 really starts to shine with bullets in the 60-85gr range as long as the rifle is throated and has the twist rate to accommodate the longer and heavier projectiles.

Winchester isn't any better and needs to get back to trying hard to compete for long range hunters dollars by repeating production of Model 70's as capable as the Sharp Shooter and Laredo they produced years ago.

Both are more than capable of producing sub MOA production guns with med/heavy barrels with a twist rate capable of handling the new heavy/long for caliber bullets.

If all they are going to is try to appeal to the Wal-Mart crowd of gunslingers it won't be long before they run out of places to market their wares and people to shoot them.

Just look at most of the "advice on a new build" threads right here, most of the suggestions start with just grabbing a model 700 from the local pawnshop and throw everything away but the exaction and start over.

I personally love the model 70 action for numerous reasons and it pains me to see the Model 70 relegated to an ever shrinking portion of the market and it's nobody's fault but Winchester's.