Tendency of heavier bullets to boost muzzle energy

[richalexander97]

Was wondering if anyone has had experiences of getting an energy boost if they simply upped the bullet weight (without an increase in charge)
I know that swept voulume greatly influences muzzle energy, for example a 300 black will have huge energy in 10' barrels

But was wondering if you went from a 40grain 223, up to a 65grain.
(Keeping the powder capacity constant)

Do you think it would add power, seeing as the bullet stays in the barrel for longer...?

 

[Bfh_auto]

Was wondering if anyone has had experiences of getting an energy boost if they simply upped the bullet weight (without an increase in charge)
I know that swept voulume greatly influences muzzle energy, for example a 300 black will have huge energy in 10' barrels

But was wondering if you went from a 40grain 223, up to a 65grain.
(Keeping the powder capacity constant)

Do you think it would add power, seeing as the bullet stays in the barrel for longer...?

Increasing bullet weight with the same powder charge will increase pressure.
Theoretically it would. But in the real world, your gun would blow up.

 

[brasscollector]

If you look at (or do the math for) lighter vs heavier bullets and what a cartridge is capable of safely pushing them to you will see that often the heavier bullet has more energy at the muzzle anyway. No need to maintain the same powder charge and over pressure the gun to accomplish that. As for a rifle in the real world muzzle energy is almost meaningless, how often is game taken at point blank range? For a handgun it may have more merit, but I would say in that case your aim,trigger control and bullet type would be paramount to muzzle energy.

 

[Erief0g]

A heavier bullet creates more pressure as it's pushed down the barrel. The technical jargon escapes me as I'm just awake without coffee.

My post is simply this. WARNING do not change bullet weight and maintain same charge of powder.

It's possible that a light load at 40 grain may only be a max load at 65 grain but this should be worked up and all loads should be referenced to your manuals

 

[Archie]

There are two forms of energy 'in' a bullet in flight.
One is kinetic energy, based on the velocity of the projectile, squared; multiplied by the mass - not weight - of the bullet, divided by half. This is the familiar K:e: = 1/2 (m*v^2).

The other form of energy is momentum, simply mass times velocity.

One notes as velocity fades, the kinetic energy fades with the square of velocity. One also notes that since the mass of the projectile is typically the smaller numerical value, increasing the smaller number raises the total at a faster rate than increasing the larger value.

Both values are useful measures, but they indicate different things.

To your question, Bfh auto is correct. Which is what all the loading manuals warn against.

 

[Erief0g]

Theoretically it would. But in the real world, your gun would blow up.

To your question, Bfh auto is correct. Which is what all the loading manuals warn against.

A much more scientific explanation of DO NOT TRY THIS

 

[LaneP]

Always stay within the confines of published load data. Then you can safely substitute heavier for lighter bullets and make the corresponding adjustment to keep operating pressures at safe levels.

 

[richalexander97]

So your saying that if I went from a 65 to 40, I'd need less charge, otherwise the pressure would be too high.

Does that mean that rounds like the 77grain army round has much less charge, and gets most of its energy from the heavy bullets dwell time?

 

[Erief0g]

My bold print and double warning may seem a bit over the top. My initial review saw that the OP is new to the forum. Welcome aboard!
With that said I wanted to make sure the proper work up was used.

Like I said, barely awake when posting and coffee is bringing me back to life.

Glad you found the forum richalexander97, it's a great place to learn from like minded people

 

[GoldieMI]

So your saying that if I went from a 65 to 40, I'd need less charge, otherwise the pressure would be too high.

actually a max book charge for 60 grain might be lower than the recommended starting charge for a 40 grain
here's an example straight from Hodgdon Reloading

 

[Erief0g]

Thank you GoldiMI, I was about to reference that and you got it!

 

[Walkalong]

But was wondering if you went from a 40grain 223, up to a 65grain.
(Keeping the powder capacity constant)

This was the question, and everyone has it right, no, without adjusting the powder charge using published data, you can't just substitute a heavier bullet.

So your saying that if I went from a 65 to 40, I'd need less charge, otherwise the pressure would be too high.

This is not what he was replying to, he was replying to your question about substituting a heavier bullet, not a lighter one, that is a completely different question.

If you are serious about these questions you need to do some reading about bullet weights vs charge weights and gain some understanding about how it works.

 

[Aletheia]

So your saying that if I went from a 65 to 40, I'd need less charge, otherwise the pressure would be too high.

Does that mean that rounds like the 77grain army round has much less charge, and gets most of its energy from the heavy bullets dwell time?

Your posts reveal serious and, somewhat dangerous, misunderstanding. If you are thinking about loading your own ammunition, it is vital that you do some real work to find out about the physics of guns and projectiles before you actually load anything. There are lots of good sources, both books and on line, but you really need to educate yourself carefully so you can understand the relationships between powder charges and bullet weight, and a shooting forum is not a very good place to do the kind of research you need to do because whole volumes need to be understood. No one on a forum has the time to write those volumes for you, and there are many on forums that do not actually understand internal and external ballistics well enough to be sure you are getting facts and information rather than myths and legends. Please buy some (and I mean more than one) loading manuals, or go on line to read manufacturers (bullet or powder makers have lots of good information on line) load manuals to help you understand the physics you are trying to comprehend.

 

[jmr40]

Using energy numbers to compare, or predict bullet performance can be very misleading. The information CAN be useful, but it's complicated. Too complicated to explain in a few sentences. In short, if you keep everything else the same and double the bullet weight you double the energy. If you keep everything else the same and double the velocity you quadruple the energy. But that doesn't mean the lighter bullet with 4X the energy is better. And in the real world that doesn't happen. When you increase bullet weight you will have to reduce velocity unless you move up to a cartridge holding far more powder.

A few things.

When you go to a heavier bullet within the same caliber the heavier bullets are longer. Longer bullets take up more space in the cartridge case leaving less room for powder. A 77 gr bullet couldn't physically have the same amount of powder in a case as a 55 gr bullet. But you could use a powder charge meant for a 77 gr bullet and load a lighter bullet with it safely. But doing so would result in a very weak load. Lighter bullets need more powder to generate the same pressure.

If you were to detonate 30 gr of smokeless powder laying loose on the ground, or in a cartridge case with no bullet it would produce very little energy. Smokeless powder generates more power with greater resistance. So even if you did have the same amount of powder behind a 77 gr bullet the pressure generated would be far more than it would generate behind a 55 gr bullet. Very possibly enough to blow up the gun,

There are advantages, and disadvantages to heavier bullets within the same caliber. Heavier will be slower at the muzzle. But since they tend to be more aerodynamic heavier bullets will retain that speed better at long range. A 50 gr bullet may be faster at the muzzle and with more energy, but a 75 gr bullet may be faster at 500 yards and will have much more energy since it is not only hitting faster, but with a heavier bullet.

Also heavier bullets within the same caliber penetrate deeper into what ever you're shooting which could be important.

 

[reddog81]

So your saying that if I went from a 65 to 40, I'd need less charge, otherwise the pressure would be too high.

Does that mean that rounds like the 77grain army round has much less charge, and gets most of its energy from the heavy bullets dwell time?

The heavier bullet takes up more space in the case. Pressure is measured in PSI or Pounds per Square Inch. More bullet in the case means fewer Square Inch's for the powder and the gas. Less space for the same amount of powder will result in high pressure in that smaller space. Additionally a heavier bullet takes more pressure to get started moving. These are basic concepts covered in every reloading manual.

 

[film495]

look at hodgdon's web site and put in two bullet weights and the rest of the specs the same.
you'll see a trend where the heavier projectile will list a lower charge weight.

so - yea, to the OP - if you are inside the reloading specs, a heavier projectile can create more muzzle nrg for the same charge, but - there are a lot of variables. I've considered reloading .223 recently, and the heavier bullet is less likely to drift with a crosswind at long range, but - also, depending on the rifle twist - the projectile has to be in tune with the rifling. I forget which way it works, but if you go too heavy or too light, you'll be all over the pace or the bullets will tumble and not stabilize correctly.

muzzle nrg is also, one factor in effective power on a target - and bullet type or ammo choice is probably more important than 100fps here or there; say the difference between a full metal jacket round, and a soft point, or hollow point, all other factors being equal; each of the three bullet types will interact with a target very differently - in a way that is subtantially different.

 

[Obturation]

The heavier bullet takes up more space in the case. Pressure is measured in PSI or Pounds per Square Inch. More bullet in the case means fewer Square Inch's for the powder and the gas. Less space for the same amount of powder will result in high pressure in that smaller space. Additionally a heavier bullet takes more pressure to get started moving. These are basic concepts covered in every reloading manual.

This.

Less powder for heavier bullets , seems backwards but minor case capacity differences change pressure dramatically.
Heavier bullets create more muzzle energy with less powder. Win/win

 

[richalexander97]

Hi i seem to have been misunderstood.
I'm well aware about longer bullets swallowing powder capacity, and sticking to recommended pressures.
Also I'm well aware that heavier bullets retain energy better at range.

My question was really unrelated to pressures and powder.

It was more to do with barrel ballistics.... dwell time in the barrel. The idea that a heavy bullet might gain the equivalent of a 'good swept volume'. Like the 300black.

I wonder If u took a 90grain 223 from a 24' barrel for example.... would it exceed the usual 1300ft lbs

But it seems that it doesn't make a major difference.

 

[reddog81]

I don’t follow... Swept volume or volume inside of the barrel remains constant regardless of bullet weight.

bullet dwell time is a function of how fast the bullet is moving. A slower bullet will be in the barrel for a longer period of time. Generally heavier bullets are moving slower and are in the barrel longer because they are moving slower.

Longer barrels allow for bullets to accelerate for more time. Are you asking if a longer barrel is more advantageous for a heavier bullet? Or something similar to that concept?

 

[richalexander97]

By Swept volume I referred to larger cal bullets which obviously get more boost from any barrel length.

I asked if heavy small cal bullets could sort of emulate this performance by being heavy.

The weighty bullet spends more time in barrel thus in theory it gets more push from the propellants.

I suppose my question could apply to ultra short barrels, for example 55grain would have poor energy in 7.5inch. Perhaps a. 77 would fare better.

 

[fxvr5]

By Swept volume I referred to larger cal bullets which obviously get more boost from any barrel length.

The weighty bullet spends more time in barrel thus in theory it gets more push from the propellants.

No clue what this means. It sound nonsensical.

 

[Bfh_auto]

By Swept volume I referred to larger cal bullets which obviously get more boost from any barrel length.

I asked if heavy small cal bullets could sort of emulate this performance by being heavy.

The weighty bullet spends more time in barrel thus in theory it gets more push from the propellants.

I suppose my question could apply to ultra short barrels, for example 55grain would have poor energy in 7.5inch. Perhaps a. 77 would fare better.

The amount of gain from barrel length is more a ratio of cartridge capacity to projectile diameter.
You can seat the heavier bullet to a longer overall length to keep the capacity the same.
If you load to the maximum safe pressure for the two bullet weights. The lighter bullet will see more increase in velocity for barrel length.

60gr 24.6gr@3086.
35gr 24.5gr@3555.

You should think about either reading or rereading the first few chapters of a reloading manual.

 

[LoonWulf]

By Swept volume I referred to larger cal bullets which obviously get more boost from any barrel length.

I asked if heavy small cal bullets could sort of emulate this performance by being heavy.

The weighty bullet spends more time in barrel thus in theory it gets more push from the propellants.

I suppose my question could apply to ultra short barrels, for example 55grain would have poor energy in 7.5inch. Perhaps a. 77 would fare better.

Lemme reword this a little and see if im close to concept in question.

Does a heavier bullet staying under pressure (assuming the curve is the same) LONGER (which it does, since it slower) allow greater transfer of potential energy to the projectile? And is it enough to make a noticeable difference between a middle weight and a heavy?

 

[Archie]

So your saying that if I went from a 65 to 40, I'd need less charge, otherwise the pressure would be too high.

Does that mean that rounds like the 77grain army round has much less charge, and gets most of its energy from the heavy bullets dwell time?

You have the concept backward: All things remaining equal, the heavier the bullet, the lighter the powder charge. By changing one condition - the powder from one burn rate to another, or the caliber, or case capacity - this may not hold true.

The 'dwell time' or as I understand you, "time in barrel being pushed by the burning powder" means nothing. At least as far as my experience and study leads me to believe. However, I encourage you to study and - carefully - experiment with the idea and keep notes and information. A number of things have been learned by hard headed refusal to accept what someone else said.

 

[Walkalong]

My question was really unrelated to pressures and powder.

No it wasn't, you don't get one without the other.