overthinking reloading - bullet weights?

[paulnyc]

I am reading Applied Ballistics for Long Range Shooting by Bryan Litz. Just finished chapter 5 on wind deflection. My take away is that you should use the heaviest bullet possible with the lowest ballistic coefficient. This reduces lag time and therefore wind deflection to a minimum. So why not follow this? Why would people use lighter bullets. if I am shooting .338 lapua do I use Nosler 180 grain bullets, or Sierra 300 grain bullets?

Thoughts? Comments?

 

[Suasponte]

Re: overthinking reloading - bullet weights?

Heavier bullets, More Powder, slower FPS, and greater Recoil!

Shooting 210SMK's at 200-300 meters is a waste. IMHO.

Lots of guys shoot 168 out to 400m and then switch to the heavier 175's 190's and 210's from 400 out to 1000.

The heaveir the bullet typically the Higher the BC. Weight plus BC will reduce wind deflection.

Terry

 

[Lindy]

Re: overthinking reloading - bullet weights?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">My take away is that you should use the heaviest bullet possible with the lowest ballistic coefficient.</div></div>

Back to the book. What you took away is not what he said.

Bryan said, and I quote:

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">In a trade-off between low BC (light weight) bullets at high speed compared to high BC (heavy) bullets at reduced speed, the high BC bullets at lower speed will produce less lag time and less wind deflection.</div></div>

(p. 86)

Heavier bullets have <span style="font-weight: bold">higher</span> BCs than lighter ones.

 

[4Rail_Gunner]

Re: overthinking reloading - bullet weights?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: paulnyc</div><div class="ubbcode-body">I am reading Applied Ballistics for Long Range Shooting by Bryan Litz. Just finished chapter 5 on wind deflection. My take away is that you should use the heaviest bullet possible with the lowest ballistic coefficient. This reduces lag time and therefore wind deflection to a minimum. So why not follow this? Why would people use lighter bullets. if I am shooting .338 lapua do I use Nosler 180 grain bullets, or Sierra 300 grain bullets?

Thoughts? Comments?

</div></div>

Depends what range you are shooting to I guess.
For across the course shooting 300 gr would be the ticket.
I personally do not load for certain distances, I load for across the course shooting.
Point Blank to 1050 yards all the same load.
So I pick the heaviest bullet I can with the Highest BC.

 

[paulnyc]

Re: overthinking reloading - bullet weights?

im looking at page 77 - "in conclusion, minimum lag time will always be realized by the highest BC (heaviest) bullet available in the caliber"

 

[paulnyc]

Re: overthinking reloading - bullet weights?

sorry, meant highest bc not lowest

 

[paulnyc]

Re: overthinking reloading - bullet weights?

wait a sec - a bullet with a high BC is LESS efficient - why would this be effected less by the wind that a more efficient (lower) BC bullet - I'm a little confused -

 

[Country]

Re: overthinking reloading - bullet weights?

Yes you are confused. The higher the BC number for a particular drag function the more efficient the bullet is at reducing drag in flight.
The statement " highest BC heaviest bullet in the caliber is missleading.
As the BC goes up and the bullet has a more efficient shape for reducing drag the weight goes down. This happens because longer ogives have less core material in them and boat tails have less core material.
The barrel twist can only stabalisea a certain max length bullet . So as you change the design of a bullet to resist more drag you lighten the bullet you can actually use accurately for that barrel twist.
If you want the high BC and the longer ( heavier) bullet you have to go toa tighter twist barrel.
However accuracy is not just about BC and drag it's also about velocity barriers . If you have a bullet that is so heavy you can not propel it fast enough to stay above the speed of sound for the range you want to shoot then as it passes through that barrier it can become inaccurate .
For LR target shooting you go for the highest BC bullet that you can keep supersonic until after it passes the range you want to shoot at. If that's 1000 yards then your load needs to stay supersonic past 1000. An example is a Palma bullet for 308W it is much lighter than other 308W bullets can be but it is able to stay supersonic for longer in the 308 case capacity. This makes it potentially more accurate than a heavier slower bullet that transends the sound barrier before you want it to.
There are many other factors that make a bullet accurate or not accurate not related to BC or velocity directly .
The statement that heavier bullets have higher BC's is just not right not in all cases . Many new low drag designs are showing BC's higher than older heavier bullets . The 155 Sierra Palam bullet has a higher BC than the heavier 168 Match king at 1000 yards.

A single BC quoted at some point in the velocity curve can not predict the whole trajectory path accurately and therfore over the whole ballistic range the bullet shows a different BC at every point you sample.
If you study ballistic data you see funny things. The BC can suddenly go down while transending the sound barrier then suddenly go back up after it passes through compared to the whole trajectory . This is the destabalising effect of the transonic zone.