Bullet weight vs velocity

[ohiohunter]

We all know heavy and fast bullets resist outside forces the most but we can't have it all and we're shooting projectiles, not lasers.

So when does the time of flight become a hinderance to heavier projectiles? Of course this will vary gun to gun but surly we can get it down to a generalization of calibers.

Is it better to push a 210gr 2400fps or a 168gr at 2700fps? Where is optimum performance found?

 

[varmintH8R]

I would argue that it depends almost entirely on what you are asking the cartridge to do. For instance, if you are looking to hunt deer at ranges between 50 and 350 yards, speed and flat shooting might be your key criteria (little to no hold-over).

If you are setting up for elk at 1200 yards, you would want the most retained energy / highest bc/ most wind resistant bullet as possible.

Moose at 50-150 yds, you may look at heavy controlled expansion bullets with no consideration for bc.

I don't subscribe to the one-size fits all approach - there are enough options out there to let you pick what is best for your application.

 

[ohiohunter]

Killing paper up to 1000yds maybe further. Out of a 280 and 308.

 

[varmintH8R]

Maybe some of the BR guys will chime in with more/better advice than I can give. My opinion would be to pick the highest BC bullet that is practical in the rifle/caliber, that shoots accurately, and that will remain supersonic past my longest expected range...

 

[MontanaRifleman]

Killing paper up to 1000yds maybe further. Out of a 280 and 308.

Whatever bullet is most accurate in your rifle. Most will be using a heavier high BC VLD type bullet for this type of shooting. My process of elimination would be to run the the bullets BC's and velocities to see which is bucking wind best at that range, then develop loads for maybe 2 or 3 and pick the most accurate in my rifle.

 

[stomp442]

Since your hunting paper I would go for the heaviest high b.c. bullet I could get my rifle to shoot well.for me that would be something in the 200 grain range for the 308 and probably a 168 out of the 280. The difference in flight time between a 168 Berger at 2700fps and a 210 at 2400fps is only .02 seconds at 1000 yards because of the higher b.c. bullet being able to retain velocity better at long range.

 

[BrentM]

I would also think that paper does not care about terminal ballistics so speed is not as important. For example berger says 1800 fps minimum for expansion so techinically that means when your bullet is under that speed at whatever distance that is, your done. Pick the distance you wish to shoot and find the chambering that gets you there. I think a 308 is a proven chamber for paper work out to 1000 but probably not something you would ever shoot an elk with.

 

[ohiohunter]

I think everyone is slightly missing the objective. I'm wondering if the slower heavier bullet will drift more or less than a lighter bullet going faster, ie time of flight. At what point is accuracy (in wind) hindered by low velocity and increased surface area?

Hunting/ terminal performance is 100% irrelevant here.

 

[MontanaRifleman]

I think everyone is slightly missing the objective. I'm wondering if the slower heavier bullet will drift more or less than a lighter bullet going faster, ie time of flight. At what point is accuracy (in wind) hindered by low velocity and increased surface area?

Hunting/ terminal performance is 100% irrelevant here.

No, not missing the point at all. That's what ballistic calculator's are for. If you go back and read my post I said run the numbers and see which bucks the wind best.

A heavy high BC bullet will almost always buck wind better, at all ranges, than a lighter lower BC bullet.

There are two things and two things only that affect wind drift. They are velocity and BC. However, you almost always have to give up one for the other because to get more BC, you need more SD (weight) and to get more velocity you have to give up weight. In the final analysis, BC almost always trumps velocity.

 

[BrentM]

6.5 specs vs a 308 @1000 yards, 5 mph full value wind.

140 vld at 2980 2.4 MOA
160 vld at 2700 2.4 MOA

180 nosler accubond at 2700 3.5 MOA
165 nosler BT. at 2800 3.5MOA


BC has more to do with it than anything.

Two examples take the 180 AB and make it .600 BC vs .507 with same speed and drift is 2.8. Take the .507 BC but add 200 fps and the drift is 3.1.

To further my view point the BC difference on the 6.5 bullets is .617 vs .680. The 308 bullets have similar issues in that the heavier bullet has a higher BC rating.

Shoot the highest BC you can at the fastest rate. This is why guys love the wildcat 338's etc for extreme LR.

 

[ohiohunter]

Montana, statement was towards the post referencing hunting.

I don't have enough of my own data to punch actual numbers into a calc but I know there are plenty of people here that do. I understand the theory and speculation, but I'd like to hear about someone w/ actual velocities from different weighted (bc) bullets then the calc can do the rest.

Def appreciate the input.

 

[MontanaRifleman]

Montana, statement was towards the post referencing hunting.

I don't have enough of my own data to punch actual numbers into a calc but I know there are plenty of people here that do. I understand the theory and speculation, but I'd like to hear about someone w/ actual velocities from different weighted (bc) bullets then the calc can do the rest.

Def appreciate the input.

I have run hundreds of ballistic comparisons and the heavy high BC bullet always does best in the wind. That said, the difference is usually small for low drag (VLD) bullets. I have used my own data and data that I have dug up by searching the internet. In my own experiences I have found 10 gr of weight = 100 fps of velocity in the .308 cal and 5 gr of weight = 100 fps in the 25 cal.

So if you are shooting the 215 hybrid in the 300 WM @ 3000 fps then you can expect to push the 185's at about 3300 fps

When running those velocities and the corresponding BC's you get this @ 1000 yds and 10 mph wind...

215's, 52" drift
185's, 58.7" drift


This is always the result when comparing apples to apples. The heavier, slower bullet with same basic form factor always does better.

 

[ohiohunter]

Perfect. Thank you.