Does Ratio of BC to Gr Weight Matter?

[raider1v1]

I was looking over the choices of bullets for a 243 and was wondering if people took the ratio into effect? From my line of thinking it would take the "best" balanced bullet between its BC and its weight. Here are the numbers that i was using and bullets that i was looking at. I have the numbers there below, but i cant get them to format correctly so i just took a screenshot.

 

[427Cobra]

Re: Does Ratio of BC to Gr Weight Matter?

IMHO the numbers Berger and Tubb gives on there respective BC is pretty close, some Hornady pills are low and some high, Sierra are close but never more than stated BC, my rule of thumb is always shoot the heaviest bullet my tube will stabilize,

 

[bward]

Re: Does Ratio of BC to Gr Weight Matter?

When I'm evaluating bullets I always take weight into consideration similar to how you have done above. Like Cobra said though, you have to start with accurate BC's for it to be an accurate analysis. I have no experience with the Nosler 105, but I am going to have to call BS on that BC. No experience with Cutting Edge, but the 105 Hybrid from Berger is the best 6mm bullet out there in my opinion.

 

[Temp9]

Re: Does Ratio of BC to Gr Weight Matter?

My method is similar to 427Cobra's, but I go with the highest BC bullet I can stabilize and afford.

As a general rule of thumb, lighter bullets can be pushed to higher velocities to allow you to shoot flatter. Higher BC bullets, which are generally heavier, allow you to buck wind better. I wouldn't worry about the ratio. Wind is harder to deal with than drop, so flat shooting is not really a concern for us.

By the way, the BC for the Nosler 105gr is incorrect on your chart (and on Midway's website). The actual value is .517.

 

[raider1v1]

Re: Does Ratio of BC to Gr Weight Matter?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Temp9</div><div class="ubbcode-body">My method is similar to 427Cobra's, but I go with the highest BC bullet I can stabilize and afford.

As a general rule of thumb, lighter bullets can be pushed to higher velocities to allow you to shoot flatter. Higher BC bullets, which are generally heavier, allow you to buck wind better. I wouldn't worry about the ratio. Wind is harder to deal with than drop, so flat shooting is not really a concern for us.

By the way, the BC for the Nosler 105gr is incorrect on your chart (and on Midway's website). The actual value is .517. </div></div>

ah, that would explain that. it was suspicuously high.

about shooting the heaviest, when i compare the hornay 105 to the dtac 115, in shooter, the 105 comes out on top with less drop and just a very small bit more of wind. thats what got me thinking about how to 'balance out' the combination of bc and gr

 

[Temp9]

Re: Does Ratio of BC to Gr Weight Matter?

Yes, the Hornady probably has less wind drift at short ranges, as well. You really start to see the DTAC's advantage at long range, where it really matters. Basically, I wouldn't trade BC for lower weight, but if I can get a high BC bullet that weighs less, that's good.

 

[Fred_C_Dobbs]

Re: Does Ratio of BC to Gr Weight Matter?

Considering that BC already incorporates the effect of bullet mass (weight), I don't have a clue what it is you're hoping to accomplish by this ratio bidness.

 

[raider1v1]

Re: Does Ratio of BC to Gr Weight Matter?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fred_C_Dobbs</div><div class="ubbcode-body">Considering that BC already incorporates the effect of bullet mass (weight), I don't have a clue what it is you're hoping to accomplish by this ratio bidness. </div></div>

just something i thought of that might help me choose between the berger, hornady, cutting edge, and DTAC. especially since i only see the dtac's sold in 500 rd boxes.

 

[bward]

Re: Does Ratio of BC to Gr Weight Matter?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fred_C_Dobbs</div><div class="ubbcode-body">Considering that BC already incorporates the effect of bullet mass (weight), I don't have a clue what it is you're hoping to accomplish by this ratio bidness.</div></div>

Exactly, since BC does incorporate the weight of the bullet, by doing an analysis where you can somewhat equalize the weights you can get a better picture of what bullet is designed better. For instance, look at the 115 DTAC compared to the 105 Hybrid. From just looking at BC's it appears the DTAC would easily outperform the Hybrid, but when you take away the advantage of weight you see that the Hybrid and the DTAC are almost identical and will have almost the same wind drift at distance since you will be able to push the Hybrids roughly 100 FPS faster.

 

[raider1v1]

Re: Does Ratio of BC to Gr Weight Matter?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bward</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fred_C_Dobbs</div><div class="ubbcode-body">Considering that BC already incorporates the effect of bullet mass (weight), I don't have a clue what it is you're hoping to accomplish by this ratio bidness.</div></div>

Exactly, since BC does incorporate the weight of the bullet, by doing an analysis where you can somewhat equalize the weights you can get a better picture of what bullet is designed better. For instance, look at the 115 DTAC compared to the 105 Hybrid. From just looking at BC's it appears the DTAC would easily outperform the Hybrid, but when you take away the advantage of weight you see that the Hybrid and the DTAC are almost identical and will have almost the same wind drift at distance since you will be able to push the Hybrids roughly 100 FPS faster. </div></div>

thats what i was thinking as i compared the 105 hornady to the 115 dtac. since the hornady was faster it had less drop. the wind was pretty equal unless i was shooting in over 25+mph

 

[Gunny81]

Re: Does Ratio of BC to Gr Weight Matter?

I think the sectional density is also directly related to the higher bc and weight. generally a heavier projectile is longer and the sd goes up. am I wrong?

 

[Bob 964]

Re: Does Ratio of BC to Gr Weight Matter?

What is important is the ratio of sectional density to G7BC. Dividing the sectional density by the G7BC gives you the form factor of a bullet. The form factor is a measure of a bullet's drag as compared to the drag of the standard G7 projectile. Form factors greater than 1.0 are bad. Form factors less than 1.0 are good. The lower the form factor, the less drag the bullet has and the more efficiently it flies.

It's a better measure than BC alone because BC includes the bullet's mass and drag in a single number. Some bullets may have a high BC just because they are heavy. These bullets won't perform as well as the high BC would suggest.

Bryan Litz had a good article on this subject. I think it was in a May 2011 Berger Bulletin. Should be easy to find if you are interested.

 

[BryanLitz]

Re: Does Ratio of BC to Gr Weight Matter?

Bob nailed it.

Your analysis is very insightful because as Bob says, form factors are a measure of how efficient a bullet is. In other words, how much velocity retaining *bang* you get for your mass *buck*.

Your spreadsheet is sort of calculating the inverse of the G1 form factor, but not accounting for caliber. The conventional (and more useful) way is to look at the G7 form factor. Here's the article Bob was referring to which explains it in depth:

http://02b0516.netsolhost.com/blog1/2011/05/16/form-factors-a-useful-analysis-tool/

Take care,
-Bryan

 

[Bob 964]

Re: Does Ratio of BC to Gr Weight Matter?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan Litz</div><div class="ubbcode-body">Bob nailed it.

Your analysis is very insightful because as Bob says, form factors are a measure of how efficient a bullet is. In other words, how much velocity retaining *bang* you get for your mass *buck*.

Your spreadsheet is sort of calculating the inverse of the G1 form factor, but not accounting for caliber. The conventional (and more useful) way is to look at the G7 form factor. Here's the article Bob was referring to which explains it in depth:

http://02b0516.netsolhost.com/blog1/2011/05/16/form-factors-a-useful-analysis-tool/

Take care,
-Bryan </div></div>

You taught me well Bryan.

 

[raider1v1]

Re: Does Ratio of BC to Gr Weight Matter?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan Litz</div><div class="ubbcode-body">Bob nailed it.

Your analysis is very insightful because as Bob says, form factors are a measure of how efficient a bullet is. In other words, how much velocity retaining *bang* you get for your mass *buck*.

Your spreadsheet is sort of calculating the inverse of the G1 form factor, but not accounting for caliber. The conventional (and more useful) way is to look at the G7 form factor. Here's the article Bob was referring to which explains it in depth:

http://02b0516.netsolhost.com/blog1/2011/05/16/form-factors-a-useful-analysis-tool/

Take care,
-Bryan </div></div>

Wow! Thanks Bryan! This pretty much is the answer of all answers. I guess I was on the right track, just not comparing the correct attributes.

Is there a listing or a way to calculate the G7 form factor? Usually the information listed is the weight, G1 BC, length (sometimes), sectional density.

 

[BryanLitz]

Re: Does Ratio of BC to Gr Weight Matter?

The G7 form factor is the sectional density divided by the G7 BC.

 

[raider1v1]

Re: Does Ratio of BC to Gr Weight Matter?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan Litz</div><div class="ubbcode-body">The G7 form factor is the sectional density divided by the G7 BC. </div></div>

Is there a way to calculate the G7 BC if its not published?

 

[BryanLitz]

Re: Does Ratio of BC to Gr Weight Matter?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Raider1v1</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan Litz</div><div class="ubbcode-body">The G7 form factor is the sectional density divided by the G7 BC. </div></div>

Is there a way to calculate the G7 BC if its not published? </div></div>

Not exactly, but you can estimate it by multiplying the G1 BC by 0.51.

This works best if the G1 BC you start with is an <span style="text-decoration: underline">accurate long range average</span>. If you start with an inflated or 'high speed' G1 BC, obviously it will skew the G7 BC and form factor.

-Bryan

 

[GreatGonzo]

Re: Does Ratio of BC to Gr Weight Matter?

Well, since it hasn't really been mentioned, If you want to get a good handle on the concept, you should really check out Bryan's book. It has tested form factors, G1s, and G7s for virtually every bullet you would be interested in as well as the theory and mathematics behind it. It also has some useful info on wind drift and gyroscopic stability. Some of it is much higher level than you may need, but the bullet resource is worth the price of admission.

 

[raider1v1]

Re: Does Ratio of BC to Gr Weight Matter?

Thanks for all the info so far guys, so far it looks like berger is in the top two spots.

i think that im going to start with them and see how they will do.

 

[Bob 964]

Re: Does Ratio of BC to Gr Weight Matter?

That's what I do. I don't test/shoot bullets with form factors equal to or greater than 1.0.