7mm-08 vs. 7x57: Pressure

20 July 2003, 14:20

<9.3x62>

I am sitting here with some pressure tested loads, both with 160 gr Sierra BT, and same barrel length (24").

7mm-08: 48.5 gr Re19 w/ 56,400 psi
7x57: 49 gr Re19 w/ 45,500 psi

Both loads produce the same velocity, about 2670 fps.

Here's the question: Is this enough pressure difference to make the 7x57 a safer (in terms of excess pressure) and more reliable (in terms of extraction) choice when hunting in areas with huge temperature swings within each day (like many parts of Africa)?

20 July 2003, 15:12

Major Caliber

Maybe, neither load generates high pressure. The 7x57 would feed better in a Mauser action.

20 July 2003, 16:09

Atkinson

The British found out a long time ago the bigger the case the less pressure..Thats why double rifle cases are so damn long....

Based on your finding, is why the 7x57 will leave the 7-08 sucking hind tit in power when handloaded....got more room for powder and like in most instances the big dog sleeps on the poarch....

21 July 2003, 05:16

<JOHAN>

quote:
Originally posted by Atkinson:

Based on your finding, is why the 7x57 will leave the 7-08 sucking hind tit in power when handloaded.

Atkinson, now the big green will get angry on you
[Big Grin]

I would say that 7X57 is the one to goo. More classic, finding ammo is not a trouble and with handloads it will do anything the 7-08 will and a tad more. Haveing a 7X57 /275 rigby is to have a piece of hunting history [Eek!]

/ JOHAN

21 July 2003, 05:44

Wstrnhuntr

quote:
Originally posted by 9.3x62:
Here's the question: Is this enough pressure difference to make the 7x57 a safer (in terms of excess pressure) and more reliable (in terms of extraction) choice when hunting in areas with huge temperature swings within each day (like many parts of Africa)?

I would say thats a reeasonable assumption, but the relative strength of the action(S) needs to be taken into account as well. How did you obtain the pressure figures?

21 July 2003, 07:46

<9.3x62>

Let's presume the same action, say, a 700.

The pressure numbers were taken from an Alliant reloading pamphlet I picked up a while back.

21 July 2003, 08:31

Paul B

[QUOTE]Originally posted by 9.3x62:
[qb]I am sitting here with some pressure tested loads, both with 160 gr Sierra BT, and same barrel length (24").

7mm-08: 48.5 gr Re19 w/ 56,400 psi
7x57: 49 gr Re19 w/ 45,500 psi

Both loads produce the same velocity, about 2670 fps. [END QUOTE]

Something here doesn't stike me as quite right. How can a load with a pressure of 45,500 PSI squirt a bullet of 160 gr. at the same velocity as a load with a pressure of 56,400 PSI?
Speer's #13 manual shows a velocity of 2570 FPS from the same charge of RL-19. They also state that the load was worked up to a max pressure of 50,000 CUP.
I know a 7x57 can be loaded a bit hotter than the 7-08, although Ken Waters said he could not do it with his rifles, but it's the dispariyrt between the two pressures that is bothering me.
Paul B.

[ 07-20-2003, 23:46: Message edited by: Paul B ]

21 July 2003, 09:04

leo-too

The .416 rem. mag and .416 rigby produce nearly the same velocities with factory ammo so what's the powder difference between the two? The rigby is known for low pressure in that caverness case. The rem. has been accused of overly high pressure at times.

21 July 2003, 09:53

Atkinson

Good example Leo, and a proper answer to Pauls question...

I can load my 7x57 Brno 21 or 22F to duplicate the .280 Rem..simply because it has a 06 lenth magazine and an extremely long throat..I can seat a 175 gr. Hornady Spt. half way to the cannalure...that gives me a lot of powder space..I get 2900 plus with 160 gr. Noslers and 2700 with 175's...these are max loads but very safe in my rifle and I have been shooting them for many years..Only one powder will do this however and that is a hefty dose of H414, it is considerably over book max btw, so I won't suggest it as surly some one would try this in their standard chamber and lock it up or worse...

I noticed Barsness said this could not be done and that he had tested it...He is dead wrong on the 7x57...It is simply another way of improving the case to give it the same capacity of a 7x57 AI....

Amazingly enough the 130 gr. Speers shoot great in these Brnos, 3/4" in mine, and they have to jump a mile to reach the rifling, another disputed fact as some say that is not good for accuracy, and granted sometimes its not, but that or anything else is written in stone when it comes to rifles.

These gun writers/experts should understand that each gun is a inity unto itself, and that is for sure. Some do but some don't....

21 July 2003, 11:22

<eldeguello>

Yes, if you choose to keep it loaded light, like your quoted load. Since the 7X57mm uses the same case as the 6mm Remington, it will perform about the same vs the 7mm/08 as the 6mm Rem does vs the .243 Win., (better!!) if you choose to so load it! [Big Grin]

21 July 2003, 11:26

<eldeguello>

Atkinson, I have about a box of old Remington 125-grain Corelokts left that were made originally for the .280 Rem. They also shoot very well in my 7X57, as do the Speer 130's.

The 125 is a good deer bullet at around 3100 FPS. I wish I could find some more of these old bullets!!

21 July 2003, 13:12

<9.3x62>

Paul:

I wish Speer (and all other reloading manuals) would report pressure for each load. Also, the OAL for the pressure test I reported is a bit longer and the barrel was 2" longer as compared to the Speer manual. Also, these results are with a Sierra bullet - perhaps the bearing surface and jacket density is a bit different...

Here's another comparison from the same source using the 139 Hornady:

7mm-08 52 gr Re19: 58,000 psi
7x57 52 gr Re19: 49,000 psi

Here both loads produced about 2845 fps or so. Again, same barrel length of 24". As I look through all of these loads, the 7x57 seems to be able to replicate 7mm-08 velocities with anywhere from 7000-11000 less psi. The same seems to hold for the 260 and the 6.5x55.

22 July 2003, 05:24

Paul B

9.3x62. I am in total agreement with your comment that the reloading manusals should give pressure data, and it should also be noted whether it is in CUP. or PSI. Frankly, I think all CUP data should be redone and posted in PSI to level the playing field considering there is no way to compare the two. This gets back to my point from my earlier post one the PSI figures. In the first case, there is a 10,900 PSI difference. In the second example from your last post, there is a 9,000 PSI difference.
The 7x57 has always been loaded to a max pressure of 48,000 PSI, later changed to CUP in deference to the old 93 and 95 Mausers and old Remington rolling block rifles. Most of the time, if my research is correct, pressure were kept more to about 42,000 CUP, with the 48,000 CUP being the allowable not to exceed maximum pressure. Considering that there is an average of 9,900 PSI difference between the 7x57 data and the 7-08 data, I cannot see both cartridges delivering anywhere near the same velocity. I mean, how can it deliver the same velocity with 19 percent less pressure?
I'll be the first to admit I'm not the brightest light on this forum, or even on the planet, but it just does not seem possible to me that two cartridges with that great a disparity in pressure could shoot the same weight bullet at near equal speed. [Confused]

as hell!
Paul B.

22 July 2003, 05:52

<9.3x62>

Paul:

I am becoming a bit suspicious myself. Perhaps the Alliant pamphlet has failed to note that the 7x57 pressures were actually CUP units, whereas the 7mm-08 pressures are PSI units. I found an online version of this data, check it out and see what you think:

http://recipes.alliantpowder.com/rg.taf?_function=centerfire&step=1

9.3

23 July 2003, 06:52

<eldeguello>

quote:
I am becoming a bit suspicious myself. Perhaps the Alliant pamphlet has failed to note that the 7x57 pressures were actually CUP units, whereas the 7mm-08 pressures are PSI units. I found an online version of this data, check it out and see what you think:

No No No No! The way a 7X57mm can produce the same muzzle velocity with the same bullet at lower peak pressure than a 7mm/'08 is by using a larger charge of slower powder! It reaches a lower overall peak pressure, but sustains the push for a longer period of the total bore time of the bullet, resulting in the same final velocity at the muzzle! Just the same as a slower powder will produce a higher muzzle velocity than a faster powder, if both are loaded to give EQUAL peak pressures!

[ 07-22-2003, 21:54: Message edited by: eldeguello ]

23 July 2003, 07:10

<9.3x62>

Yes, but in this instance we are talking about EXACTLY the same powder and EXACTLY the same charge. [Confused]

23 July 2003, 08:14

beemanbeme

That's what has me confused. The 7x57 case is bigger so with the same loads the pressure in the 7x57 should be lower but the velocity yield should be lower also. I have one of each so I may have to try this out. Equal charges of H4895 should give the same results, right?

23 July 2003, 09:59

Paul B

9.3x62. I really think we're looking at apples and oranges here, or should I say CUP and PSI?
Supposedly, the new Lyman manual has all "new" data. If that's the case, why, for exapmle is data for the 7x57 still in CUP and the 7-08 in PSI. All new data, MY ASS!.I feel ripped off on that one, and pretty much that way on the new Hornady and Sierra manuals as well. More and more downloading of old classic cartridges. What a waste of my time and money.
Paul B. [Mad]

as hell!

23 July 2003, 11:27

mikethebear

Both loads have the same energy (same weight - same powder). So maybe that is something we should explore. Doesn't make sense to me either, as I would think the higher pressure would push harder. However that is only the peak pressure, and we don't know the profile of the pressure as the bullet moves down the barrel. Sorry I don't have any answers or opinions [Big Grin]

23 July 2003, 12:12

bartsche

mike the bear got it right. same energy different pressure / volume curve different variable acceleration. You would have to see both curves to be sure.

29 July 2003, 17:25

low_tech

Area under the curve, if I remember something of the math that I have had, it has been said before in this threadbut, area under the pressure curve will tell the story, lower overall peak pressure for a greater amount of time will yeild higher vel than a higher peak, but for a shorter duration, you are trying to evalute a line with a single data point, you need to see more than one point on that line in order to say something(significant)about that line. The function of that line is the best. I have exhusted both my spelling and math quioent [Razz]

for the night.
low_tech

01 August 2003, 17:03

Atkinson

Eldeguello,

Not to fret, just use the 130 Speer Flat base, it is the best deer bullet I have used in the 7x57 and the 284...It knocks a 50 cent size exit hole in them every time as Elmer used to say...

01 August 2003, 17:30

bill smith

Ray Atkinson: in your first post you made reference to the difference in case capacity making an apparently big difference in pressure. in the Barnes manual, they show the 7x57 having a capacity of 55.5 grains and the 7-08 with a capacity of 52.2 grains. does such a small difference really have a telling effect? the difference is only a little less than 6%.

02 August 2003, 01:00

<Savage 99>

If indeed the charges are the same and the powders are of the same lot then the testing accuracy is off. The larger cartridge should produce less velocity as it's burning with less pressure. The potential energy in each grain of powder may be the same but a higher percentage of the total possible energy will be extracted from the vessel operating at higher pressure. No different than a higher compression engine.

Of the standard rim "short" 7mm's the 284 Winchester holds the most powder. I agree with Ray that the 130 Speer 7mm flat base is an excellent hunting bullet.

In general since none of the above cartridges are really all that powerful and thus superior for long range hunting it does not matter a lot which one is used. In this class the .308 Winchester is the best round IMHO.

03 August 2003, 03:49

<eldeguello>

quote:
mike the bear got it right. same energy different pressure / volume curve different variable acceleration. You would have to see both curves to be sure.

I agree!

Atkinson: Thanks for the tip RE: 130-grain Speer flatbase. I did shoot a couple small central TX white-tails with the Nosler 120-grain Solid-base-boattails that preceded the Ballistic Tip bullets. Boy, were they explosive! Blew away a lot of meat, but still exited (MV +- 3100 FPS).