SAAMI & CIP Limits, Exceedable?

[Ray B]

Some cartridges have load limits based on the numerous weak actions in that chambering or the balloon head cases used. An example is the 45/70 where reloading manuals will specify different pressure limits for the cartridge depending on which of several actions in which the ammunition is to be fired. I'm wondering about those limits that appear to be in place for other reasons- the most common being that a load normally used in Africa is loaded lighter because 1. the temperature will cause the pressure to increase, & 2. the lighter load will make for surer extraction when getting a fresh round in the chamber is REALLY necessary.
CIP limits pressure in some cartridges at 52K, while it limits others to the more standard 62K. If someone is loading a cartridge designated by CIP for 52K, but they are using modern solid brass cases, powder that is not temperature sensitive, they have worked up the loadings, watching for signs of pressure and there is no indication of cases sticking in the chamber, brass flowing, primer flattening, etc, and the rifle being used is a modern bolt action such as the CZ550, Win 70, etc, is there any reason a shooter should limit the loads to the CIP level ? If I were to increase the load in cartridges that CIP lists a maximum load at 52K to 62K, the limit for most standard cartridges, am I being unsafe and pushing my luck? or just utilizing the potential of the cartridge/rifle?

 

[ZG47]

Double base propellants appear to be the biggest culprits with heat related pressure increases (primers second biggest). That being said, I tend to keep a woollen item handy to cover any cartridges that I leave out in the sun, despite the fact that most of my reloading has been with single base powders, Pressures need to be kept within limits but, here is the thing, as your barrel wears, it is possible to increase your propellant charges.

There is an Aussie gun writer called Nick Harvey, whose loads are sometimes described as a bit hot. One factor is that some of his rifles have had a fair bit of use before the latest data was published in his loading manuals. The data should be annotated with extracts from, or précis of, the relevant portions of his original magazine articles. This is a simple step that his critics unaccountably fail to mention.
Another factor is that when he has a rifle built in, or rebarrelled to, a relatively hot cartridge, he tends to use the appropriate European or U.S. barrel and reamer. The critics tend to be the kind of people who are always looking to use tighter barrels and apply target-style forward-bullet-seating techniques to hunting cartridges. Guess whom I trust more, Mr Harvey ... or the chancers?

Context is everything with this topic. You have to research the matter thoroughly, via reliable sources, before taking the risk.

 

[rookhawk]

CIP being European and governmental assumes the reader has responsibility and an average IQ. The result is just as you mentioned, real load data. I know specifically that 6.5x55 SE and 7x57 are much hotter in European load manuals.

SAAMI is a non-binding industry association that doesn't want to get sued, so they don't chance data that could be too hot for one decrepit 110 year old Springfield or krag jorgansen action. Thus, they lower the data overall.

Go with CIP.

 

[Pheroze]

My understanding is that pressure does not increase in a linear manner. So the edge of the envelope is not as predictable as just another half grain or so. Otherwise, my belief is that there are a lot of variables so having a well understood objective may allow for beneficial increase.

 

[rookhawk]

@Pheroze I was also told that compressing a load can have dangerous unintended consequences. My well respected gunsmith said he'd basically disown me if I ever did it.

The lesson: never compress a load unless the published data specifies it's a compressed load. This is where IMR4350 and H4350 get dangerous, they have different volumes but are relatively similar. Thus, one can be compressed creating dangerous pressures at max capacity that would not with the other.

I've seen so many errors in data, particularly for fine guns in the African calibers, that I like two sources to corroborate before I load to printed spec. (E.g. Van Walt, Wright and Woodleigh...two should agree when possible)

 

[Ray B]

To clarify the question, an example: CIP lists maximum pressure for the 404 Jeffery as 53K, while the maximum for the 458 Win Mag is 62K. Keeping everything equal (no confusion as to compressed loads, powders subject to temperature, etc) , using brass of similar make and construction, in a rifle of modern design and strength, it seems to me that the cartridges should have the same limit. My conclusion: Either the Jeffery is loaded light at 53K or the Win Mag is loaded hot at 62K, since all the variables are matched.

 

[rookhawk]

To clarify the question, an example: CIP lists maximum pressure for the 404 Jeffery as 53K, while the maximum for the 458 Win Mag is 62K. Keeping everything equal (no confusion as to compressed loads, powders subject to temperature, etc) , using brass of similar make and construction, in a rifle of modern design and strength, it seems to me that the cartridges should have the same limit. My conclusion: Either the Jeffery is loaded light at 53K or the Win Mag is loaded hot at 62K, since all the variables are matched.

@Ray B Is it possible the larger bore diameter, and thus the greater circumference of the .46 caliber bullet of the .458 creates greater resistance and pressure than the smaller circumference .42 caliber bullet from a .404?

It seems that could be one source of difference? It also could be that the straight wall case can tolerate pressure better than the necked Jeff case?

Any number of possible reasons for the difference abouve plausible?

 

[Pheroze]

To clarify the question, an example: CIP lists maximum pressure for the 404 Jeffery as 53K, while the maximum for the 458 Win Mag is 62K. Keeping everything equal (no confusion as to compressed loads, powders subject to temperature, etc) , using brass of similar make and construction, in a rifle of modern design and strength, it seems to me that the cartridges should have the same limit. My conclusion: Either the Jeffery is loaded light at 53K or the Win Mag is loaded hot at 62K, since all the variables are matched.

The physics of cartridges is a very interesting topic. I think the 404 (for example) loaded to a specific pressure and speed must be in reference to a some design optimization.

Its probably true that a given action and brass has the strength to withstand a particular pressure. The idea that the 404 could be loaded hotter because the structure can endure more pressure is what I think you are saying. But, getting a cartridge to a pressure it was not designed for may be dangerous.

My under-educated but genuinely interested understanding is that case shape will have an impact on this. The Rigby pressures I believe are much lower than the Remington Magnum but achieve equivalent speeds. The larger case was a design feature to keep pressure down. My thought is that the increase in pressure is not linear and can be affected by available space in the case, so as the case is filled past the design parameters I would be concerned that the pressure would build in unpredictable ways. Also, speed is a god predictor of pressure up to a point. Maybe the case designs anticipate the pressure curve available for a case shape, space, bullet weight etc. After which doom befalls us?

I think we are speaking to two different points but I am articulating badly my thought that you may not be able to get a particular cartridge to a pressure over its design spec safely. I understand from the Lee Manual the opposite is also true: it is unwise to load down too much as well.

 

[Shootist43]

Several recent posts have mentioned the dangerous effect African Temperatures have on cartridges. I reload in my basement, temperature year around is maintained at 70 F. What does the ambient temperature need to get to before this over pressure phenomenon begins? Assume for the moment that the rounds are kept out of the sun.

 

[rookhawk]

Several recent posts have mentioned the dangerous effect African Temperatures have on cartridges. I reload in my basement, temperature year around is maintained at 70 F. What does the ambient temperature need to get to before this over pressure phenomenon begins? Assume for the moment that the rounds are kept out of the sun.

A "loaded" question...insert groan for bad pun.

Cordite was horribly unstable at different temps 100 years ago.

Today, you're pretty good with most powders. Even IMR4350 that is not temp stable is only moving a few FPS per degree. I'd have to source it but I think it was like 60fps and corresponding pressure between 70 degrees and 100 degrees.

Put another way, if your loads are so hot they cannot handle a 1%-1.5% increase in pressure, you probably deserve bad things happening as you are way past the edge already!

Obviously, this does not pertain to you @Shootist43 so you have nothing to fear. Just google temp impact on your favorite powder for specifics. No one is using cordite anymore so don't fret much.

 

[Ray B]

In looking at the CIP website there is considerable variation in the max pressures for the multitude of cartridges listed- so my guess is that to make a valid conclusion as to the validity of CIPs listed maximum, one would need to know the criteria that CIP used in determining that number. I didn't see any explanation regarding how they arrived at the various numbers. I'm reduced to using Ken Waters' method of determining maximum loads and letting whatever number the pressure ends up being be just that, a number.

 

[ZG47]

1. Load compression is a valid technique for black powder NOT nitrocellulose (or cellulose nitrate as the chemists call it).
2. When CIP changed over to piezo measurement they put the piezo sensor in the same place as the copper (lead for pistol and shotgun) crusher. The U.S. military reportedly did the same BUT it is my understanding that SAAMI put the piezo sensor in a different place. If you wish to compare data between CIP and SAAMI you need to: firstly ascertain whether the data was obtained via crusher or piezo; and secondly, if comparing crusher to piezo or CIP piezo to SAAMI piezo you will need some obscure information that ballisticians are unlikely to give out to any Tom, Dick or Harry.
My choice, for what it is worth, is to do basic research and then select one set of data from which to develop your test series of loads.

 

[rookhawk]

What I infer from CIP is that the velocities are greater than SAAMI in many instances. Thus, I know that if I work up gradually and check for signs of pressure, I'm likely in a safe range.

You cannot trust SAAMI on 6.5x55 , 7x57 and a few others for certain.

I buy my loaded ammo from Europe for 7x57 because it actually is considerably more powerful than what is retailed in the States.

As you may note, I cannot stand SAAMI. I don't like their data, I don't like that we lack a proof house. I don't like that hey think they are better than CIP when they are not. I don't like that they are designed to protect the manufacturer's liability whereas CIP is to protect the consumer.

 

[Bob Nelson 35Whelen]

Some cartridges have load limits based on the numerous weak actions in that chambering or the balloon head cases used. An example is the 45/70 where reloading manuals will specify different pressure limits for the cartridge depending on which of several actions in which the ammunition is to be fired. I'm wondering about those limits that appear to be in place for other reasons- the most common being that a load normally used in Africa is loaded lighter because 1. the temperature will cause the pressure to increase, & 2. the lighter load will make for surer extraction when getting a fresh round in the chamber is REALLY necessary.
CIP limits pressure in some cartridges at 52K, while it limits others to the more standard 62K. If someone is loading a cartridge designated by CIP for 52K, but they are using modern solid brass cases, powder that is not temperature sensitive, they have worked up the loadings, watching for signs of pressure and there is no indication of cases sticking in the chamber, brass flowing, primer flattening, etc, and the rifle being used is a modern bolt action such as the CZ550, Win 70, etc, is there any reason a shooter should limit the loads to the CIP level ? If I were to increase the load in cartridges that CIP lists a maximum load at 52K to 62K, the limit for most standard cartridges, am I being unsafe and pushing my luck? or just utilizing the potential of the cartridge/rifle?

Ray B
CUP and PSI are entirely different
52,000 cup is up around 60,000 psi.
If you were to load to 62,000 cup both you and the rifle would need to be put back together as th at pressure is over proof load.
Yes it is possible to go over SAAMI specs but you must be a very experienced hand loader and keep a good watch for any signs of danger.
DONT ATTEMPT THIS IN AN OLD RIFLE OF UNKNOWN STRENGTH.
USE ONLY NEW MODERN ACTIONS.
never try and convert cup to psi it leads to trouble.
Never take risks.
Old cartridges can be given a boost in NEW MODERN ACTIONS as a lot of them were only loaded to 45 to 48,000 cup.
The 7mm Mauser, 280 Remington, 30/06, 35 Whelen were all under loaded but safe in OLD guns
When giving these a boost use NEW UNFIRED BRASS IN A MODERN RIFLE AND WORK UP SLOWLY TO A SAFE WORKING LOAD.
NEVER FIRE A HOTTED UP LOAD IN AN OLD RIFLE.

It very rare that you can go over book loads BUT with some old cartridges it can be done safely.
This is only my opinion and should not be taken as correct.
Bob

 

[bruce moulds]

there seems to be a great focus on cip or saami spec when it comes to pressures in reloading.
possibly a better way to look at it is what is a max safe load in your gun with that brass, those primers, those bullets with that relationship to the lands, and those primers in those conditions.
saami and cip is a good place to start, but you really need to find the max yourself by looking for case head expansion in once fired brass before the test load.
having established a max this way, you can back off some for safety sake, and potential temp increases.
now you have a load you know to be safe in your gun.
the responsibility is yours.
with respect compressing powder, some people who want to look knowledgable condemn it out of hand.
if you work up a load using standard principals and it is safe, there is no problem.
often very accurate loads are found doing this.
and bullets cannot be pushed back into the case.
bruce.

 

[Alistair]

So I guess the first question would be 'how would you even know if you've exceeded the CIP or SAAMI pressure limits? Do you have a piezo sensor?'

My second would be 'Who on earth listens to SAAMI?' I mean, the CIP loadings tend towards safety over performance as they should, but the SAAMI stuff is just anaemic.

My take, in a modern rifle, load to whatever works in your gun as indicated by pressure signs in your loads. Start low in the manual for safety, but if you end up with the most accurate load above book max with no pressure signs, then fine. No problem. My 'hot' LR competition Creedmoor loadings exceed book values on both powder charge and velocity (especially in summer), so I think it's very likely that they exceed both CIP and SAAMI pressures. That said, bolt lift is fine, no markings on the brass, not excessively flat primers and the brass still lasts more than 5 loadings, so why would I care?

On the other hand, in an older rifle you might be best served by starting low in the book charges and staying there. I have a friend with a WW1 vintage SMLE who will not exceed loads about half of the way up the published values. Seems sensible on a potentially weaker rear locking lug action using early-19th century metallurgy.

The issue comes when rifles exist in a chambering which fall in the 'vintage' range, because then all factory by necessity is loaded to the mild levels in case they end up in vintage chambers. In these cartridges (any classic British african cartridge, 45-70, 7x57, 8x57, 303, 6.5x55, possibly 30-06 etc) the factory loadings can be safely exceeded by a very great extent by the careful handloader in a modern, strong action. It's perfectly safe to do so, it just requires care, attention and the matching of loads to specific rifles.

As for compressed loads, I haven't seen issues. My only compressed loads at present are a 44 Rem Mag Marlin 1894 loading with H110 and a 375H&H load with N150. Both are within book values but compressed to around 105-110% load density. I've also tested lightly compressed loads in .270win (RL22) and 6.5CM (various powders).

On a final note, all my reloading is a single load matched to a single rifle. Therefore, the method above works fine. The idea of just working up a general load for use in multiple rifles is not something I even contemplate. If you do choose to go that route though, the load should be based on the oldest, weakest rifle it'll be used in. Don't work something up in a modern bolt gun then try and use it in an old piece. You'll have a bad day.

Al.

 

[Bob Nelson 35Whelen]

So I guess the first question would be 'how would you even know if you've exceeded the CIP or SAAMI pressure limits? Do you have a piezo sensor?'

My second would be 'Who on earth listens to SAAMI?' I mean, the CIP loadings tend towards safety over performance as they should, but the SAAMI stuff is just anaemic.

My take, in a modern rifle, load to whatever works in your gun as indicated by pressure signs in your loads. Start low in the manual for safety, but if you end up with the most accurate load above book max with no pressure signs, then fine. No problem. My 'hot' LR competition Creedmoor loadings exceed book values on both powder charge and velocity (especially in summer), so I think it's very likely that they exceed both CIP and SAAMI pressures. That said, bolt lift is fine, no markings on the brass, not excessively flat primers and the brass still lasts more than 5 loadings, so why would I care?

On the other hand, in an older rifle you might be best served by starting low in the book charges and staying there. I have a friend with a WW1 vintage SMLE who will not exceed loads about half of the way up the published values. Seems sensible on a potentially weaker rear locking lug action using early-19th century metallurgy.

The issue comes when rifles exist in a chambering which fall in the 'vintage' range, because then all factory by necessity is loaded to the mild levels in case they end up in vintage chambers. In these cartridges (any classic British african cartridge, 45-70, 7x57, 8x57, 303, 6.5x55, possibly 30-06 etc) the factory loadings can be safely exceeded by a very great extent by the careful handloader in a modern, strong action. It's perfectly safe to do so, it just requires care, attention and the matching of loads to specific rifles.

As for compressed loads, I haven't seen issues. My only compressed loads at present are a 44 Rem Mag Marlin 1894 loading with H110 and a 375H&H load with N150. Both are within book values but compressed to around 105-110% load density. I've also tested lightly compressed loads in .270win (RL22) and 6.5CM (various powders).

On a final note, all my reloading is a single load matched to a single rifle. Therefore, the method above works fine. The idea of just working up a general load for use in multiple rifles is not something I even contemplate. If you do choose to go that route though, the load should be based on the oldest, weakest rifle it'll be used in. Don't work something up in a modern bolt gun then try and use it in an old piece. You'll have a bad day.

Al.

Alistair
Mate try working out loads for a wild and wooly wildcat with no load info that's fun
Bob

 

[Alistair]

Alistair
Mate try working out loads for a wild and wooly wildcat with no load info that's fun
Bob

Ha!

I think we have different ideas of what constitutes 'fun'!

Al.

 

[7x57Joe]

Two books I can recommend are: Complete Guide to Handloading by Philip Sharp and Principals and Practice of Loading Ammunition by Earl Naramore. They may be hard to find and are dated but contain a lot of very useful information.