The "Best" big bore cartridges ever created!!!

[Northern Shooter]

The fashion in Botswana is .450 Rigby loaded with 600grns .
Solids will reach the vitals of a big bull elephant from any angle.
Never tested this personally but that’s the talk around the campfire..

I wasn't aware 600gr class projectiles were available for 458 calibers.

That has an impressive S.D. of 0.409!

 

[Uncontrolled_round_feed]

I do not…but could do a 375H&H and a 416 Rem if that’s worthwhile…

458WM, 375H&H, 416Rem, 505Gibbs

 

[Uncontrolled_round_feed]

500 Jeff with 600gr premium bullet is the ultimate big bore rifle cartridge

A respectable choice. I like the Gibbs design (esp no rebated rim) more than the Jeff’s but there is room for all around the campfire.

 

[Tug]

G'day guys here is my final revision, I've included more load and calibres and done all the calculations for recoil energy and recoil velocity myself. When I wrote my first version was quite tired and some parts of it was crude and hard to read. Hopefully this version will be a marked improvement.

please enjoy

Also is there any way I can edit my first post to replace it with the updated version?

 

[Northern Shooter]

G'day guys here is my final revision, I've included more load and calibres and done all the calculations for recoil energy and recoil velocity myself. When I wrote my first version was quite tired and some parts of it was crude and hard to read. Hopefully this version will be a marked improvement.

please enjoy

Also is there any way I can edit my first post to replace it with the updated version?

Where is the updated version?

 

[Tug]

Rationalizing Big Bore Cartridge Performance: A Data-Driven Analysis

Choosing the right big bore cartridge for hunting can be a complex decision. Often, discussions are dominated by personal preferences, anecdotes, and emotional arguments, making it challenging to objectively assess cartridge performance. To address this, this article presents a data-driven analysis of popular big bore cartridges. The aim is to rationalize cartridge performance by objectively evaluating key variables, enabling hunters and shooters to make informed choices based on their specific needs and priorities. While performance is central to this analysis, it's important to remember that personal enjoyment and historical significance are also valid aspects of cartridge selection.

Methodology: A Consistent Data Framework

For consistent and comparable analysis, factory load data serves as the default data source for this study, unless explicitly stated otherwise for specific cartridges. The data presented will focus on maximum powder loads for consistency.

Key Performance Metrics:

The following metrics were selected to provide a comprehensive assessment of cartridge performance. These metrics are crucial for understanding a cartridge's capability in big game hunting scenarios:

• Bullet Type and Weight: Specifies the bullet type used in the factory load and its weight in grains.
• Powder and Charge: Indicates the type and amount of powder used in the load (by weight).
• Maximum Velocity: The muzzle velocity of the bullet, measured in feet per second (fps).
• Energy: The kinetic energy of the bullet at the muzzle, measured in foot-pounds (ft-lbs).
• Energy Efficiency: This metric, calculated as a percentage, represents the efficiency of the cartridge in converting the chemical energy of the powder into kinetic energy of the bullet. A higher percentage indicates more efficient energy conversion.
• Momentum: Bullet momentum describes the bullet's impetus, its forward force of motion. Crucial for penetration, momentum dictates the bullet's ability to maintain forward motion as it encounters resistance. Higher momentum contributes to deeper penetration.
• Sectional Density (SD): Sectional Density is defined as the ratio of a bullet's mass to its cross-sectional area. A higher sectional density signifies a greater concentration of bullet mass within a smaller frontal area, resulting in less resistance and improved penetration through tissue and bone.
• Sectional Area (SA): This metric quantifies the bullet's cross-sectional area, determined by its caliber. Sectional area is indicative of the potential size of the wound channel created by the bullet. A larger sectional area may contribute to faster incapacitation through increased tissue damage.

Why am I not using "Taylor's knock out factor" to indicate terminal performance?

While metrics like the Taylor Knock Out factor (TKO) exist, they can be misleading. TKO can overemphasize factors like bullet mass and caliber, potentially masking deficiencies in crucial areas like sectional density. For example, a bullet with a high TKO score due to large mass and caliber might still exhibit poor sectional density, hindering its penetration capability and ultimately its effectiveness on game.

Therefore, this analysis treats Momentum, Sectional Density, and Sectional Area as independent and equally vital variables. Their functions in incapacitating game are distinct and non-overlapping:

• Low Sectional Density: Impairs bullet penetration, limiting the bullet's ability to reach vital organs.
• Low Momentum: Results in rapid deceleration of the bullet upon impact, reducing penetration depth and potentially hindering vital organ damage.
• Low Sectional Area: Restricts the size of the wound channel, potentially slowing incapacitation due to reduced tissue damage area.

Secondly, Managing recoil is crucial for accurate and comfortable shooting, especially with powerful cartridges. Here are some key factors to consider:

• Recoil Velocity:
  
  • Velocities below 15 FPS are generally considered safe for extended shooting sessions with proper technique.
  • Velocities exceeding 15 FPS increase the risk of developing a flinch, with cumulative effects over time, and present a small risk of headache with prolonged use.
  • Velocities above 20 FPS significantly increase the risk of severe headaches, also with cumulative effects.
  • The U.S. military restricts personnel to weapons generating no more than 60 ft-lbs of recoil energy, deeming higher levels unacceptable.
  • Cartridges producing over 50 ft-lbs require significant preparation and mastery of recoil management techniques.
  • For cartridges generating over 70 ft-lbs, a heavier rifle (over 10 pounds) or recoil mitigation devices (e.g., muzzle brakes, specialized clothing) are strongly recommended.

Personal Analysis: Evaluating Big Bore Cartridges

The .458 Caliber Group

The 458 Caliber Group consistently demonstrates high performance across key metrics. The .458 Win Mag and .458 Lott, in particular, achieve exceptional energy efficiency while maintaining strong killing potential and moderate recoil. This balance explains their popularity among game rangers and for culling operations in Africa. Similarly, the .450 Rigby and .460 Wby Mag offer impressive performance, with their terminal effectiveness often rivaling, and in some cases even surpassing, certain .50 caliber cartridges. However, the increased recoil of the .450 Rigby, and especially the .460 Wby Mag, may exceed the physical tolerance of many shooters. Notably, the .458 caliber group stands out for its strong performance across all metrics (indicated by green color-coding), reflecting a well-rounded and highly effective cartridge design for hunting large game."


The 50 Caliber Group

The .505 Gibbs and 500 Jeffery boast impressive killing power and are a serious step up from the 458 Winchester Mag and 458 Lott in terminal performance and are best described as stopping cartridges designed to fit in a versatile bolt action rifle, primarily driven by its large sectional area and momentum values.

However, this performance comes at a significant cost, and the recoil energy for both the 500 Jeffery and 505 Gibbs are beyond the capabilities of most shooters. While the 500 Jeffey has significantly less recoil energy than the 505 Gibs up to 15 ft Lbs less. Due to its reduced powder charge because of its impressive cartridge efficiency (31 percent).

The 505 Gibbs exhibits the lowest energy conversion efficiency among the cartridges analyzed with (525gr bullets), raising questions about whether the substantial recoil generated is fully justified by its relative performance gains compared to more efficient cartridges.

The .40 Caliber Group​

The .404 Jeffery, while some factory load data reflects performance close to its original design, other loads demonstrate greater potential with either increased power or reduced recoil (42 ft-lbs) by lowering the ejecta mass of the powder charge, all while maintaining impressive terminal performance.

Meanwhile, the .416 Rigby, originally designed for use with cordite propellants, exhibits lower energy conversion efficiency—a common trait of cartridges developed for early smokeless powders. However, its 450-grain load represents a significant improvement, offering better terminal performance while also reducing recoil by 8 ft-lbs from 55 ft-lbs, making it a more manageable option for shooters seeking a balance of power and comfort.

The .405 Winchester, despite achieving a high Taylor Knock-Out (TKO) factor, is poorly suited for thick-skinned dangerous game due to its limitations in momentum (leading to quicker loss of forward motion) and sectional density (reducing penetration). Lastly, the .416 Weatherby Magnum stands out for its high momentum and sectional density, but its comparatively lower sectional area may contribute to excessive penetration, increasing the risk of wounding animals beyond the intended target.

The .358 to .375 Caliber Group​

Cartridges in the .358 to .375 caliber range generally exhibit lower sectional area and momentum compared to larger caliber groups. However, with the exception of the last three cartridges in this group, they offer the benefit of significantly reduced recoil compared to their larger counterparts.

The .375 caliber group, in particular, retains significant value due to its versatility—excelling in plains game hunting with good ballistic trajectories and a wide selection of bullets suited for both dangerous game and standard hunting applications.

Within this group, the .375 H&H Magnum presents a balanced performance profile with manageable recoil, widespread popularity, and ammunition availability, making it a well-rounded choice. Similarly, the .375 Ruger delivers commendable performance, especially given its optimized design for shorter, 20-inch barrels, making it a more compact alternative with similar ballistic effectiveness.

The .35 Whelen, while exhibiting high energy efficiency, lags behind the other cartridges in this group in overall killing power metrics and is included primarily for illustrative purposes.

The Double Rifle Cartridges Group

The analysis of double rifle cartridges offers valuable insights, particularly highlighting the .500 Nitro Express with outstanding terminal performance values. It surpasses the .470 Nitro Express in key performance metrics, delivering 16% greater sectional area and 11% higher momentum. This represents a significant improvement in stopping power, explaining why it's a favorite among elephant hunters, making it a more efficient option. However, this success comes with the downside of producing 12 to 19 more ft-lbs of recoil energy, depending on the load, than the .470 Nitro Express.

Among these traditional big-game cartridges, the .450 Nitro Express emerges as a well-balanced choice, combining strong energy efficiency, excellent terminal performance, and more manageable recoil. Its effectiveness during the golden age of African hunting cemented its reputation, and even today, it remains a highly capable and versatile option for hunters seeking a potent yet controllable big bore cartridge. Given its historical significance and practical advantages, a renewed appreciation for the .450 Nitro Express should encourage greater availability of factory double rifles chambered in this caliber.

The .450/400 Nitro Express 3" is a highlight among these cartridges for being the only one close to producing under 15 fps of Recoil Velocity and 36 ft-lbs of recoil energy. Its excellent terminal performance, combined with its "shootability", allows hunters to hit their intended target zone with quick follow-up shots, something that cannot be matched by any other double rifle. This makes it an outstanding option for hunters who prioritize accuracy and speed while still demanding powerful performance from their double rifle.

One Cartridge to Hunt the World?

When considering the best all-around cartridge for hunting a wide range of game, the strong contenders are the .375 H&H and the .416 Remington Magnum. The .416 Remington Magnum excels in terminal performance, especially with 400-grain bullets, which show a notable advantage in momentum (25%), sectional area (25%), and sectional density (10%) compared to the .375 H&H. However, with the introduction of new 350-grain .375-caliber bullets, the performance gap between these two cartridges has narrowed significantly.

As Dr. Kevin Robinson points out, the 350-grain .375-caliber bullet now performs nearly as well as the 400-grain .40-caliber bullet on large game. The numbers between the two are very close, with the .40-caliber round having slightly more momentum and a larger sectional area, while the .375-caliber round has a notably higher sectional density (0.356 compared to 0.33).

Additionally, the .375 H&H offers two advantages over the .416 Remington Magnum. First, it benefits from a wider availability of high-ballistic coefficient (BC) hunting bullets, making it potentially more suitable for long-range hunting, such as sheep hunting. However, with advances from Cutting-Edge Bullets, this advantage may soon diminish.


The second advantage of the .375 H&H is its significantly reduced recoil—up to 20 to 30 percent less recoil energy compared to the .416 Remington Magnum, depending on the load. This makes the .375 H&H a more attractive option for recoil-sensitive hunters or those who need to shoot larger volumes, as the reduced recoil can make the shooter more comfortable and effective.

This concludes my analysis. What aspects of the data did you find most surprising? Has this analysis shifted your perspective on which cartridge you would choose for your next hunt?

 

[Tug]

"The accompanying table presents a comprehensive evaluation of various big bore cartridges, employing a weighted scoring system to balance desirable attributes against the detrimental effects of recoil. To ensure objective comparisons, raw data was normalized using Z-scores and subsequently shifted to positive values. Weights were assigned to each attribute—momentum (1.3), sectional density (1.45), sectional area (1.2), recoil velocity (1.2), and recoil energy (1.0)—reflecting their relative importance in the context of dangerous game hunting. Sectional density (1.45) received the highest weight, as its role in deep penetration through thick hides and bone is considered paramount for reliable and ethical performance. Momentum (1.3) was also highly weighted, as it ensures the bullet maintains its drive through dense tissues. Sectional area (1.2) was weighted to acknowledge its importance in creating a significant wound channel for rapid blood loss and tissue damage. Recoil velocity (1.2) and recoil energy (1.0) were both included as counterweights, reflecting their combined impact on shooter control and fatigue. Recoil velocity, specifically, was given a high weight due to its direct impact on shooter control, specifically its ability to cause the development of a flinch and induce headaches. Recoil energy was included to reflect its impact on both shooter control and fatigue. The resulting 'Cartridge Score' provides a comprehensive metric, allowing for direct comparisons and highlighting cartridges that offer an optimal balance between terminal performance and manageable recoil."

This graph was just a bit of fun, I wouldn't put much stock in it.

 

[John Telford]

Very interesting reading thanks @Tug
I will try and post work done by Game Ranger Richard Sowery and his metrics for various calibers.

 

[Northern Shooter]

That was a great write up, are you submitting that for your thesis?

 

[Riflecrank]

Tug,
To your excellent analysis of DG efficacy of rifles
I add also the practicality in all the other realms of shooting and hunting
(suitable firearms, ammo and components availability and variety, etc., etc., etc. ...),
and there is clearly a "BEST":
The .458 Winchester Magnum aka the ".458 Winner Magnus."

Thanks to Buckstix for this cartoon with a little addition of the "WIN" by me:

 

[Northern Shooter]

458 WM really is the Everyman’s Dangerous Game cartridge.

My only wish is that more ammo companies would produce new loads for it.

I’d likely to see 350gr @ 2,500 fps and a hot 500gr @ 2,200 fps.

 

[Riflecrank]

Tug,
You have a TYPO in the recoil table.
The .458 Lott (Speer) load shows a 350-gr bullet in the first listing of load data,
but it got switched to a 500-gr DGS bullet in the recoil table, for the .458 Lott (Speer) entry.

I hope that did not have any effect on your excellent results overall,
and it was just a typo in the bullet naming box of the table.

 

[Tug]

Tug,
You have a TYPO in the recoil table.
The .458 Lott (Speer) load shows a 350-gr bullet in the first listing of load data,
but it got switched to a 500-gr DGS bullet in the recoil table, for the .458 Lott (Speer) entry.

I hope that did not have any effect on your excellent results overall,
and it was just a typo in the bullet naming box of the table.

Thank you for that, I was bound to make a mistake. Luckily the calculation is still correct. which surprised me, not much difference between a fast 350gr and a moderate 500gr.

Very interesting reading thanks @Tug
I will try and post work done by Game Ranger Richard Sowery and his metrics for various calibers.

Thank you, I would appreciate that. It would be nice to know how they went about it; they obviously have mountains of field experience as a game ranger.

That was a great write up, are you submitting that for your thesis?

No it was just for myself and fun. Now I don't have burning questions in my head anymore

Tug,
To your excellent analysis of DG efficacy of rifles
I add also the practicality in all the other realms of shooting and hunting
(suitable firearms, ammo and components availability and variety, etc., etc., etc. ...),
and there is clearly a "BEST":
The .458 Winchester Magnum aka the ".458 Winner Magnus."

Thanks to Buckstix for this cartoon with a little addition of the "WIN" by me:

When you put the power of the 450 Nitro express into a modern bolt action rifle cartridge, you really can't help but be successful.

 

[Aussie Chris]

((sips drink, yeah this is going to be a big one))

Well, I'm back and have decided after feedback from my last thread to improve my data table to analyse the best big bore cartridges for you!

Why do all of this?
I would like to rationalise the performance of cartridges and their bullets. To logically make clear the performance variables of each cartridge. To allow people to make their own concise choices based on the variables important for them. As hunters and shooters, we compare cartridge performances too much based on our own/others' emotions and anecdotes, stories. Which can make the job of choosing tools to fit our needs more difficult than it needs to be sometimes! Hopefully this table can make the task visually simple while grounding our perspectives. (Note I'm not against people choosing based on other choices, eg, fun, historical value, etc.)

So how does it work and how did I put it together?

First, I've decided to use Hornady factory loads for all the cartridges, different companies will have different results. But Hornady is the only one with the Nitro express cartridge data, and I decided consistency is key. So I'll only be using Hornady data. The data shown will be using their maximum loads. The data will be colour coded, red is bad and green is good.

On the tables you will find:
- Bullet type and weight
- Powder used and amount of
- Max velocity
-Energy of the bullet
- Energy efficiency of the cartridge ( i.e how much energy does the cartridge convert from the powder's chemical to the bullet kinetic energy in percentage)
- Bullets Momentum ( momentum is the bullet impetus, its forward force of motion, which is vital for reaching the vitals)
- Sectional density ( The ratio of a bullet mass to its cross-sectional area. Useful in determining the bullet's penetrative capability in the animal.)
- Sectional area ( The area of the bullet, determined by the diameter of its calibre. Useful in determining the size of the bullet's wounding channel into the animal)

Why am I not using "Taylor's knock out factor"
I believe the TKO number can be a misleading indicator of the performance of a bullet on animals and is arbitrary, for example, a bullet can have an impressive score due to large mass and calibre, but have poor sectional density, which will affect the bullet's performance, incapacitating an animal effectively.

I believe Momentum, sectional density, and sectional area should be considered as independent variables, they cannot be judged or combined. Their mechanical functions are unique and each is equally important as the other. Their role in incapacitating animals is independent of each other.

With low sectional density, a bullet will struggle to penetrate.
With low momentum, a bullet's forward motion is quickly stopped.
With low sectional area, a bullet's wound channel will be small inside the animal, slowing incapacitation.

Without further ado,


View attachment 670212

View attachment 670214


Personal analysis

The best cartridges for big game hunting are, without a doubt, the 458 Win Mag and the 458 Lott, they combine great kill potential with amazing efficiencies with low powder charges comparatively. This leaves little doubt in my mind why these cartridges are the preferred culling and game ranger cartridges of Africa today! The 450 Rigby scored exceptionally good as well. However, you are paying for that performance with a lot more recoil and are over the physical limit of most people. Likewise with the 460 Wby Mag

The 458 calibre are the only ones to have green in every box, every other calibre group had compromises. The 505 Gibbs has impressive killing power, sadly that killing power is on both ends of the rifle, with lowest energy conversion on the list!!! Some people may ask themselves if the lemon is worth the squeeze with this one.

The next best choice would have to be the 400 calibres, with the 416 Remington mag may be the finest choice among them, followed by the 416 Ruger, which is like a unicorn, nobody has seen them ever! The 404 Jeffery data does not illustrate its full modern potential but is close to the performance of its original loading. The 416 Rigby, of course, is designed for cordite high temperature pressure sensitivities, which reminds me of sensitive people when I criticise its poor energy conversion efficiency. The 405 Winchester is a great example of a cartridge with a good TKO factor but a terrible cartridge for hunting thick-skinned dangerous game due to poor momentum and sectional density. Lastly, the 416 Wby Mag highlights its high momentum sectional density value, but its low out of balance sectional area value, which might explain why it is prone to over penetrating and wounding animals standing behind the target.

The .358 to 375 calibre all suffer from the same problems, namely a lack of sectional area and a lack of momentum. But except the last 3 cartridges in the group, benefit from reduced recoil. This 375 group will always be valued for its versatility for hunting plains, good trajectories and being the legal minimum for hunting dangerous game. Out of the group, the 375 H&H is the most balanced in performance with moderate recoil. With the benefit of being the most popular. The 375 Rugers performance is great for only a 20-inch barrel, and the 35 Whelen, while greatly efficient, is lacking in the killing power compared to the rest.

Lastly, the double rifle cartridges. The data surprised and highlighted why the 500 Nitro express is the preferred elephant cartridge for good reason, beating the 470 Nitro express in all variables except for producing slightly recoil. With 16 per cent more sectional area and 11 per cent more momentum. It is a significant upgrade in performance for a smaller cartridge case as well, being only 3" long compared to 3 1/4" of the 470 Nitro express. Out of all the cartridges, the 450 Nitro express is the most balanced in efficiency, killing power and recoil, and it is little surprising why it was the most popular cartridge during Africa's golden years before its ban. I think it's time for people to appreciate it again, as the do-it-all powerhouse it truly was!!! (Please start making more factory double rifles in it!)

For recoil reference

Rifle Recoil Table

If you made it this far, thank you very much for reading.

All criticisms and opinions welcomed.

Tug.

Regarding your last comment: Yeah. I really love the 450NE. I have nothing against the 470NE at all, and I love the fact that it is slightly bottle necked. To me that’s the main positive although no one else seems to agree haha. (I just meant that it is going to be easier to feed in a hurry after your first two shots if you need to reload under stress).
But I’ve ordered a 450NE from Heym. I really struggled to decide between the 450NE and the 500NE. I decided that one day, if I can afford a trophy elephant hunt I’ll just go out and buy a Westley Richard’s 500NE, but until that day I’ll be better off with the 450NE for the practice. Also, it’s got a huge selection of bullets. It can be loaded to be a genuine ferrel pig gun all the way up to a legit elephant gun. With 500gr bullets it should punch well above its weight in terms of penetration. It’s also what I’d consider to be the start of the genuine stopping cartridges, but being at the start, having the least recoil with all the benefits that has (speed and accuracy). I know there is no magical line between where a stopping cartridge starts and stops but I just feel I’d be a little hesitant with a 416 or 404 in my hands when tracking a wounded buff into thick scrub where as I feel a 450NE, even with 480gr projectiles is essentially a 458wm / Lott on a head brain shot, and if you don’t consider either of those stoppers then not many bolt actions would be.
So I second your remarks - make more doubles in the 450NE!

 

[farmer_john]

Very cool. Just one question you have a powder min and max but only one velocity what powder load are youbusing for listed velocities?

 

[Schüler Jumbo]

I have a question regarding operating pressure vs perceived recoil. For our example let’s compare the .416 Remington and the .416 Rigby. Let’s assume rifles are the same barrel length and weight. Both are loaded with identical 400 grain bullets at a velocity of 2400 fps. The .416 Remington cartridge design operates at 65,000 psi (SAAMI) and the .416 Rigby operates at 52,000 psi (SAAMI). Do you expect the Remington to have a higher perceived recoil due to the higher operating pressure acting on the rifleman in a shorter recoil impulse time span?

 

[Mark A Ouellette]

I have a question regarding operating pressure vs perceived recoil. For our example let’s compare the .416 Remington and the .416 Rigby. Let’s assume rifles are the same barrel length and weight. Both are loaded with identical 400 grain bullets at a velocity of 2400 fps. The .416 Remington cartridge design operates at 65,000 psi (SAAMI) and the .416 Rigby operates at 52,000 psi (SAAMI). Do you expect the Remington to have a higher perceived recoil due to the higher operating pressure acting on the rifleman in a shorter recoil impulse time span?

Recoil is factored with the total weight of the ejecta and the velocity.

ShootersCalculator.com | Recoil Calculator

An online calculator that calculates the recoil energy, impulse, and velocity of a firearm according to the firearm's weight, powder charge, bullet weight, and bullet muzzle velocity.

shooterscalculator.com

Because the lower pressure .416 Rigby requires more powder by weight than the higher pressure .416 Rem, the Rigby's recoil will be higher for the same bullet weight and muzzle velocity.

I've posted this recoil chart a dozen times before. Here it is again,

Some trap shooters think they can tell the difference between slow and fast burning powders for the same shot weight and velocity. Most others do not...

 

[PCC600]

What a beast!

You don't happen to have a 450 Rigby or 416 Rigby on hand do you to show the visual comparison vs the Gibbs?

Here you go . A Rigby 450 magnum . Single square bridge action with 22 inch step down barrel at top . Below a 505 G single square bridge with a 25 inch ( massive ) barrel . I shoot 500-550 grain pills through the 450 and 600 grain through the 505 . Both devastating on buff . But the 505 really is something else .

 

[Schüler Jumbo]

Okay. Thank you Mark. On the chart comparing the 500 gr .470 NE with 106 grains powder weight at 2100 fps to the 570 gr .500 NE with 101 grains powder weight at 2150 fps recoil is higher with the .500 because of the bullet weight ejecta and additional 50 fps velocity? Both rifles are the same weight indicating same barrel length and both operate at 40,000 psi, how does the .500 gain 50 fps over the .470 with less powder?

 

[Schüler Jumbo]

And when recoil is described as a “big push” vs a “sharp jab” that is the velocity component attributing to the “sharp jab”? As I understand it now, the big push perceived recoil can well be a greater force than the perceived sharp jab hitting the rifleman. I was putting too much emphasis on operating pressure. Thanks!