Pressure limits in older european calibers, - do they make sense with modern actions and brass??

[harrygrey382]

As to why - why do you load any cartridge to its full? Why not just not bother to max any of them out? Factory loadings aside. Otherwise, I feel like I’ve written most of what I can on this subject. That is - 7x57 cases are fully endorsed by cartridge manufacturers, licensing bodies and rifle manufacturers to run 65k psi in the form of 6mm rem. These aren’t “made to another set of rules”, they are the same cases run through a different neck die with a different head stamp. There is literally no difference between a 7x57 case, 257r and 6mm rem case by the same manufacturer. Even right back in the early 50s 7x57 cases were holding this pressure. This is according to friends who have cut them side by side, weighed them, and a Bertram Brass (who manufacture both - or should i say the one case) employee. The cases were never redesigned to run higher pressure - they were necked down by wild catters and then commercialised with no change to the case. There has never been any hint of evidence to the contrary, just speculation by one member here.

Given, in the case of 7x57, it is established the cartridges are capable of higher pressure it is then the rifles (well technically it’s more the barrel) that are under question. But this is a pretty well covered can of worms and I doubt we need to discuss it. I am however sceptical that 6.5x55 cases aren’t able to take 65k psi as safely and consistently as “rated” cases. But as I haven’t explored this thoroughly I won’t try and claim it. One or two ruptured 6.5x55 cases don’t prove much - how many blown 270, 308 etc. cases are knocking around? What’s to say the 6.5x55 didn’t cop a pressure load that would blow any brass case?

Another point that makes the whole thing a bit pointless is it’s very unlikely beginner reloaders will be pushing the envelope due to the majority of well founded advice to follow guidelines. It’s only when people research and gain an understanding of operating systems they question the reasons behind rules and see that some may purely be founded on outdated arbitrary numbers and are in reality a guide. These people don’t need to be told anything, they can work it out.

It’s not like we’re a panel of board members getting ready to put out an update to CIP/SAAMI pressure ratings or an offical reloading publication - we’re a bunch of blokes voicing our opinions on an independent hunting forum, and I assume most people take this for what it’s worth which is fruit for further thought.

Of course, the Major floor in this argument is how do you know when you’re there - not, is it theoretically safe. With a 270 you follow the max load in the book, if you’re out to exceed a book level how do you know how much further to go? Obviously you use a chrony and look for pressure signs, and see what quick load suggests, but it’s not overly precise. I guess you could send some loads off to be tested, or run a pressure transducer, or a copper crush, but it’s all heading to pain-in-the-arse territory. It is the one hurdle to loading 7x57 to its full potential I reckon.

Some reloading manuals warn about these pressure limits to be used in older rifles. Often stating to reduce loads by x from their published data if using in older rifles. It does not say increase by x if using in newer rifles.
a different cartridge/rifle simple.

Books do tell you to exceed SAAMI pressure levels (28k psi) for 45-70 in modern rifles (50k psi in Ruger no1, 35k psi in Marlin 1895). There may well be more examples

 

[harrygrey382]

so a few questions seems to have arisen, but mainly:

- why are/were these pressure limits originally imposed, and why wernt they changed as actions and brass grew better ?

as seen above, there is some discussion as to wether the (potential limits) of modern brass for these cartridges really is a valid reason to limit the pressure to the listed sami and cip limits, or not.

Good on ya for starting a thread on it where we can all have it out!
I limits did change a little as time progressed, but not by a lot. Mostly as a nod to older rifles with softer barrels and actions still being in regular use in these calibers.

I do actually think it’s still wise to keep the CIP limits where they are - with the risk of repeating myself if you’re an experienced reloader with a decent knowledge and understanding you’ll know when/if someone of them can be exceeded. Let people who don’t, stick to the limits rigorously. But you clearly have a good handle on it!

 

[scrumbag]

I think the "modern pressures" argument is an interesting one and I looked into it a bit as I own a 257 Roberts.

In terms of +P for 257 Roberts, it is is more moving the pressure up to ~308W levels rather than the anemic pressures originally stated when Remmington "Legitimised" the cartridge back in the 1920s.*

I've got / had batches of 257 Roberts and 257 Roberts +P brass and bar usual maker to maker variance I wouldn't have said there was a significant difference in the weights and cases volumes.

There is a recognition in published data of different pressures.

For example Nosler and Speer state their data is for 257 Roberts +P where as Sierra's data is labelled standard 257 Roberts data - Not a lot of charge weight difference though especially with heavier 117 / 120gr bullets.

Older manuals seem to state that for +P data, there is about a 2gr reduction in maximum charge weight.

I think that the really interesting area for +P is with pistol ammo where particularly in Semi-auto pistols, the chamber is not always fully supported where the feed ramp comes in.

45 ACP / 45 Super is an interesting example of this. 45 Super has the same exterior case dimensions as 45 ACP but has thicker brass to be able to function at higher pressures - In things like 1911 designs these pressures would bulge the cases into the void where the feed ramp is. (In semi-autos you also have to think about your spring weights to keep your slide velocities reasonable but that's another story).

Scrummy

 

[Heym SR20]

Here’s my take on these arguments

1) the first generation of cartridges epitomised by the 7x57 have been performing very well and killing lots of game with something close to their original loadings. Load up a 140gn to 156gn bullet, with a muzzle velocity of a bit above 2,500 fps up to 2700 fps and any deer within 250 yds will be dead.

You can say the same about the 30-06, 6.5x55, 8x57 or 375 H&H.

You don’t need to load them to high pressures and high velocities to get more than adequate performance.

2) There are modern cartridges - eg the 6.5 PRC that are designed to be very efficient yet provide high velocities. Modern powders give a progressive rise in pressure that accelerates the bullet down the barrel. You don’t need really high peak pressures - what you want is a good level of pressure for the whole time is in the barrel.

3) there are plenty of magnum type cartridges which use massive cases, small bullets and lots of powder to produce high velocities, at the expense of lots of noise, recoil and cost in terms of barrel life and on your wallet. Many of these are now pretty much obsolete.

We are seeing the same in car engines. A cylinder of about 450 to 500 cc is highly efficient and provides optimal burn characteristics to provide good torque and power. Its why most manufacturers now use this cylinder size, and why the four cylinder 2000 cc engine is the mainstay of most vehicle manufacturers, and rather than dropping size if cylinder, we now drop to three cylinders for small engines, and go to 6 cylinders for bigger 3 litre engines.

 

[Sharpie]

Here’s my take on these arguments

1) the first generation of cartridges epitomised by the 7x57 have been performing very well and killing lots of game with something close to their original loadings. Load up a 140gn to 156gn bullet, with a muzzle velocity of a bit above 2,500 fps up to 2700 fps and any deer within 250 yds will be dead.

You can say the same about the 30-06, 6.5x55, 8x57 or 375 H&H.

You don’t need to load them to high pressures and high velocities to get more than adequate performance.

2) There are modern cartridges - eg the 6.5 PRC that are designed to be very efficient yet provide high velocities. Modern powders give a progressive rise in pressure that accelerates the bullet down the barrel. You don’t need really high peak pressures - what you want is a good level of pressure for the whole time is in the barrel.

3) there are plenty of magnum type cartridges which use massive cases, small bullets and lots of powder to produce high velocities, at the expense of lots of noise, recoil and cost in terms of barrel life and on your wallet. Many of these are now pretty much obsolete.

We are seeing the same in car engines. A cylinder of about 450 to 500 cc is highly efficient and provides optimal burn characteristics to provide good torque and power. Its why most manufacturers now use this cylinder size, and why the four cylinder 2000 cc engine is the mainstay of most vehicle manufacturers, and rather than dropping size if cylinder, we now drop to three cylinders for small engines, and go to 6 cylinders for bigger 3 litre engines.

This is a good analogy. My GF's car (Seat) has a 1400cc 4 cylinder low compression petrol engine with an advanced turbocharger that blows it at 2 bar or more, virtually from tickover. Even with brief over-boost and knock sensors to retard the ignition if you are running it on standard pump fuel, rather than the "super" stuff, with which it can really perform to its best, for special occasions. Developing 150 BHP at full chat with an almost linear power curve. 100 HP per litre is quite normal these days, for modern petrol engines. Other models with the same 1400cc engine put out 180 hp, just down to the ECU mapping (I've researched this, there are almost no other changes other than to the exhaust and cooling systems. ISTR it revs to over 6000 RPM, beyond which there is a soft rev limiter, which may seem like a lot, but is nothing for something with 350cc per cylinder, and a very short stroke. Very over-square. Most of the time it runs around only using two cylinders, the other two being cut off by disconnecting the valves, so no pumping losses from them. Even cruising at 70 mph on the motorway on the flat. The transition is seamless, you can't tell except by the indicator in the instruments. Very torquey too, though not in the class of an olde school but still advanced 2.0 diesel that I run. Where I can mash the pedal as long as I've got about 1800 RPM, but then it tails off beyond 3000 RPM, all pretty much over by 4000 RPM, so a full power overtake requires more preparation with a downchange or two, but then risking running out of revs during the manoeuvre. Hers doesn't. Knock it down from 6th to 4th and blast away, it will keep pulling until way beyond any legal UK speeds. Basically the same (Seat) car. The diesel engine is much much heavier, all over the front wheels, and quite obvious to me. Hers is a delight to drive by comparison. Fantastically economical, far more so than my old diesel. And her front tyres have a much easier life, mine, when pushed hard on twisty roads, begin to under-steer and run a bit wide, despite my upgraded wheels and tyres. Hers does not, it's like a go-kart by comparison (not that I've ever driven a go-kart). And though we both have the same brakes, It is clear to me that mine could be better in the limit. I don't think I've ever approached the limits of hers, not for the want of trying. It's all about the mass, my car is dragging around probably the extra weight of two people, all in the wrong place.

I agree that the old-school magnums that burn 70gr or more of powder for only maybe 200 fps more MV than a lesser thing burning 50gr or less, albeit using a heavier bullet, seem as about as modern as an American big block V8 muscle car, in the modern world. Just how much more terminal energy do you really need for even the largest deer, or moose/elk at any realistic range, in European conditions ?

Just as the old military derived cartridges in the 7mm class seem just about right even in the modern world. But I don't really see the point in trying to hot-rod them, even though clearly it can be done.

There has been progress in modern chamberings, and powder developments. And no, it is not necessary to grow a trendy beard to own one (though I do have a rather splendid example, so could probably qualify for ownership one day).

As and when something like a 7mm PRC comes out, I think that might make a rather fine hunting cartridge (as well as a precision long range target shooting thing). I prefer to look forwards, not back.

 

[alberta boy]

This is a good analogy. My GF's car (Seat) has a 1400cc 4 cylinder low compression petrol engine with an advanced turbocharger that blows it at 2 bar or more, virtually from tickover. Even with brief over-boost and knock sensors to retard the ignition if you are running it on standard pump fuel, rather than the "super" stuff, with which it can really perform to its best, for special occasions. Developing 150 BHP at full chat with an almost linear power curve. 100 HP per litre is quite normal these days, for modern petrol engines. Other models with the same 1400cc engine put out 180 hp, just down to the ECU mapping (I've researched this, there are almost no other changes other than to the exhaust and cooling systems. ISTR it revs to over 6000 RPM, beyond which there is a soft rev limiter, which may seem like a lot, but is nothing for something with 350cc per cylinder, and a very short stroke. Very over-square. Most of the time it runs around only using two cylinders, the other two being cut off by disconnecting the valves, so no pumping losses from them. Even cruising at 70 mph on the motorway on the flat. The transition is seamless, you can't tell except by the indicator in the instruments. Very torquey too, though not in the class of an olde school but still advanced 2.0 diesel that I run. Where I can mash the pedal as long as I've got about 1800 RPM, but then it tails off beyond 3000 RPM, all pretty much over by 4000 RPM, so a full power overtake requires more preparation with a downchange or two, but then risking running out of revs during the manoeuvre. Hers doesn't. Knock it down from 6th to 4th and blast away, it will keep pulling until way beyond any legal UK speeds. Basically the same (Seat) car. The diesel engine is much much heavier, all over the front wheels, and quite obvious to me. Hers is a delight to drive by comparison. Fantastically economical, far more so than my old diesel. And her front tyres have a much easier life, mine, when pushed hard on twisty roads, begin to under-steer and run a bit wide, despite my upgraded wheels and tyres. Hers does not, it's like a go-kart by comparison (not that I've ever driven a go-kart). And though we both have the same brakes, It is clear to me that mine could be better in the limit. I don't think I've ever approached the limits of hers, not for the want of trying. It's all about the mass, my car is dragging around probably the extra weight of two people, all in the wrong place.

I agree that the old-school magnums that burn 70gr or more of powder for only maybe 200 fps more MV than a lesser thing burning 50gr or less, albeit using a heavier bullet, seem as about as modern as an American big block V8 muscle car, in the modern world. Just how much more terminal energy do you really need for even the largest deer, or moose/elk at any realistic range, in European conditions ?

Just as the old military derived cartridges in the 7mm class seem just about right even in the modern world. But I don't really see the point in trying to hot-rod them, even though clearly it can be done.

There has been progress in modern chamberings, and powder developments. And no, it is not necessary to grow a trendy beard to own one (though I do have a rather splendid example, so could probably qualify for ownership one day).

As and when something like a 7mm PRC comes out, I think that might make a rather fine hunting cartridge (as well as a precision long range target shooting thing). I prefer to look forwards, not back.

I agree ........... but I'm keeping my V8 Hemi , I just like how it sounds .

AB

 

[Heym SR20]

I agree ........... but I'm keeping my V8 Hemi , I just like how it sounds .

AB

Agree that I really do like the sound of V8s and best of naturally aspirated straight 6. But at £1.50 per litre (give or take a penny or two) for normal fuel, a thirsty engine really does cost a lot to run.

Ditto the sound of a big cartridge - I love the boom my 7x65r makes. Much nicer than the high pitched crack of a 243. And a big nitro express - 470 etc is just wonderful and wonderfully inefficient on powder use.

 

[alberta boy]

Agree that I really do like the sound of V8s and best of naturally aspirated straight 6. But at £1.50 per litre (give or take a penny or two) for normal fuel, a thirsty engine really does cost a lot to run.

Ditto the sound of a big cartridge - I love the boom my 7x65r makes. Much nicer than the high pitched crack of a 243. And a big nitro express - 470 etc is just wonderful and wonderfully inefficient on powder use.

1.50 pounds is a bit rich , it's $ 1.12 CDN a litre here ...... which is good , the 5.7 is a thirsty bitch .

AB

 

[harrygrey382]

I agree ........... but I'm keeping my V8 Hemi , I just like how it sounds .

AB

Hell yes - the sound of a big petrol V8 is delicious and irreplaceable. I’m more partial to an I6 though.

This is a good analogy. My GF's car (Seat) has a 1400cc 4 cylinder low compression petrol engine with an advanced turbocharger that blows it at 2 bar or more, virtually from tickover. Even with brief over-boost and knock sensors to retard the ignition if you are running it on standard pump fuel, rather than the "super" stuff, with which it can really perform to its best, for special occasions. Developing 150 BHP at full chat with an almost linear power curve. 100 HP per litre is quite normal these days, for modern petrol engines. Other models with the same 1400cc engine put out 180 hp, just down to the ECU mapping (I've researched this, there are almost no other changes other than to the exhaust and cooling systems. ISTR it revs to over 6000 RPM, beyond which there is a soft rev limiter, which may seem like a lot, but is nothing for something with 350cc per cylinder, and a very short stroke. Very over-square. Most of the time it runs around only using two cylinders, the other two being cut off by disconnecting the valves, so no pumping losses from them. Even cruising at 70 mph on the motorway on the flat. The transition is seamless, you can't tell except by the indicator in the instruments. Very torquey too, though not in the class of an olde school but still advanced 2.0 diesel that I run. Where I can mash the pedal as long as I've got about 1800 RPM, but then it tails off beyond 3000 RPM, all pretty much over by 4000 RPM, so a full power overtake requires more preparation with a downchange or two, but then risking running out of revs during the manoeuvre. Hers doesn't. Knock it down from 6th to 4th and blast away, it will keep pulling until way beyond any legal UK speeds. Basically the same (Seat) car. The diesel engine is much much heavier, all over the front wheels, and quite obvious to me. Hers is a delight to drive by comparison. Fantastically economical, far more so than my old diesel. And her front tyres have a much easier life, mine, when pushed hard on twisty roads, begin to under-steer and run a bit wide, despite my upgraded wheels and tyres. Hers does not, it's like a go-kart by comparison (not that I've ever driven a go-kart). And though we both have the same brakes, It is clear to me that mine could be better in the limit. I don't think I've ever approached the limits of hers, not for the want of trying. It's all about the mass, my car is dragging around probably the extra weight of two people, all in the wrong place.

I agree that the old-school magnums that burn 70gr or more of powder for only maybe 200 fps more MV than a lesser thing burning 50gr or less, albeit using a heavier bullet, seem as about as modern as an American big block V8 muscle car, in the modern world. Just how much more terminal energy do you really need for even the largest deer, or moose/elk at any realistic range, in European conditions ?

Just as the old military derived cartridges in the 7mm class seem just about right even in the modern world. But I don't really see the point in trying to hot-rod them, even though clearly it can be done.

There has been progress in modern chamberings, and powder developments. And no, it is not necessary to grow a trendy beard to own one (though I do have a rather splendid example, so could probably qualify for ownership one day).

As and when something like a 7mm PRC comes out, I think that might make a rather fine hunting cartridge (as well as a precision long range target shooting thing). I prefer to look forwards, not back.

There’s no doubt the latest engines perform very impressively. My 2.0tdi Golf goes like a cut snake, sticks to the road like glue and uses less fuel than it should. However, if it came to staking my life on it, no matter how extreme the conditions and distance I couldn’t chose anything but a solid axle Landcruiser with a 4.2 factory turbo 24 valve. Sounds pretty good with a 3” exhaust and minimal muffler without the feral straight through Patrol in your faceness. The pinnacle of longevity, reliability, torque/power potential and fuel
Consumption for what it does. Euro may be best for performance but the japs had reliability sewn up tight by the mid naughtiest and it was downhill from there.

Maybe a bit of an analogy with high pressure cartridges here - the more power (maybe cylinder pressure cf chamber pressure ) you get from a given engine size the less long it lasts. Hence companies like Cummins offer a warranty inversely proportional to the power out put to an engine

 

[scrumbag]

1.50 pounds is a bit rich , it's $ 1.12 CDN a litre here ...... which is good , the 5.7 is a thirsty bitch .

AB

But the response from the throttle is good!

 

[Scipio]

But the response from the throttle is good!

hehe, i bet ,D - but this old car vs new discussion, for me at least is perhaps more adapt talking on about in the old vs new rifle rifle thread, so please allow me to respond to you there instead.

 

[Heym SR20]

Getting this thread back on track - ok my bad for even mentioning automobiles - let’s not forget that many the Edwardian calibres actually produced very modern ballistics. The 7x57, or, as it was renamed, the 275 Rigby High Velocity load was a 140 gn bullet doing 2750 + fps, meanwhile the 30 Calibre cartridge 1906 Cartridge, the 30-06, was a 150gn bullet at 2,700 fps which in 1936 was raised to 2800 fps. But they were getting this with max pressure of 50,000 psi. Probably explains the long service life of Springfields and Garand rifles.

 

[Foxyboy43]

Interesting thread thanks.
it has prompted a thought (exceedingly rare these days) on the differing load data for the 6.5x55 Swedish Mauser (Swede) and the 6.5x55SE/SKAN. I know that the “Swede” refers to (or more accurately used to - they seem to have morphed into one now) the old military rifles and that Vihtavuori go so far as to provide different load data for each and indeed carry a pretty stark warning about the dangers of using modern loads in these older rifles but the question for me is why is the 6.5x55 the exception to the extent that different loads are prescribed for new/old rifles? There are many old(er) chamberings such as the Mosin Nagant where this is not the case (see what I did there) so why the 6.5s? Are the swede users a more cautious bunch, is it the development of powders, are the older rifles simply less strong than their peers or what?
Grateful for views chaps.

 

[User00040]

The 7x57, or, as it was renamed, the 275 Rigby High Velocity load was a 140 gn bullet doing 2750 + fps, meanwhile the 30 Calibre cartridge 1906 Cartridge, the 30-06, was a 150gn bullet at 2,700 fps which in 1936 was raised to 2800 fps. But they were getting this with max pressure of 50,000 psi. Probably explains the long service life of Springfields and Garand rifles.

Where did you get that data?

Not including test barrel lengths is a bit pointless.

 

[Heym SR20]

Where did you get that data?

Not including test barrel lengths is a bit pointless.

Old adverts, factory data and military specs. Would be with 24 or 26” barrels.

 

[User00040]

Old adverts

I think they were even more 'optimisic' about muzzle velocity then as some manufacturers are with ballistic coefficients now.

From what I have read, the chronographs of the time (1900's) involved firing a projectile through a silk screen to interrupt an electrical current.

There is a reason why devices such as LabRadar was developed. Optical chronographs can give different readings depending on lighting conditions and the angle from which the projectile is fired.

 

[Heym SR20]

I think they were even more 'optimisic' about muzzle velocity then as some manufacturers are with ballistic coefficients now.

From what I have read, the chronographs of the time (1900's) involved firing a projectile through a silk screen to interrupt an electrical current.

There is a reason why devices such as LabRadar was developed. Optical chronographs can give different readings depending on lighting conditions and the angle from which the projectile is fired.

A lot of the early velocities were measured with ballistic pendulums and then using lots of mathematics. They are very accurate.

 

[Bavarianbrit]

Neat video. I don't even bother trickling powder - I just use a battered old RCBS uniflow dispenser as it is much quicker. In my experience powder loads are the least finicky aspect of reloading. A few granules more or less seems to make no difference on the grouping.

I just watched the part 1 that Lee priming addon seems a faff compared to doing hand sizing as I do and having the primer tray that full looks tres dangerous to me. Does anyone else lube their inside case necks? I never do, as I want the brass alone to give me the neck tension.