What Are Considered Maximum Safe Pressures in Rifle Cartridges

[South Pender]

Perhaps this question can't be answered, as I imagine many variables need to be considered. However, I've been playing with Quickload, running a number of loads for my .270 Win., and have wondered whether the maximum loads short of "Dangerous Load-Do Not Use!" should be considered safe.

With modern hunting rifles, what pressure in PSI should be considered safe? I get it that we would want to examine fired cases for signs of excessive pressure in individual rifles, but is there a sort of general standard for safe pressure? I’ve noticed that loads generating as much as 63,000 PSI in the .270 Win. seem to be labelled safe in Quickload. These pressure figures pertain to values obtained by piezoelectric pressure gauges and not the older CUP system.

Is there an answer to this question, or does it just go back to what appears to be safe in a particular rifle?

 

[Uncle Ed]

The max chamber pressure set by the SAAMI is for the oldest and weakest action they will be fired in.

I always asked myself if I had a new Remington 700 in 30-06 why couldn't it be loaded to the same pressures as my good old .270.

 

[South Pender]

The max chamber pressure set by the SAAMI is for the oldest and weakest action they will be fired in.

I always asked myself if I had a new Remington 700 in 30-06 why couldn't it be loaded to the same pressures as my good old .270.

In Quickload, the max pressure (Pmax) by SAAMI is higher than that by CIP. In my .270 Win. runs, the SAAMI max is given as 65,000 PSI, whereas the CIP max is 62,366 PSI.

 

[FeMan]

Great question and I am interested in what some more knowledgeable have to say. QL lists the Dasher as a max pressure of 65ksi while they list the parent 6BR case as something quite lower.

It makes sense that as long as the brass can handle it, the limit is determined by the action. The design and and quality of the brass will determine how long it will last. I have run my Dasher to 65ksi per QL but the brass only lasts 2 or 3 firings. I have therefore throttled it down.

 

[ebb]

I know nothing of QL, i was looking to buy it some time back and saw some one pots that i knew to be a good rifleman and a good reloader. He called QL "the birth place of bad ideas!" I didn't think much of it at the time but I have been seeing more and more of these kinds of posts. Maybe he was right.

 

[South Pender]

I know nothing of QL, i was looking to buy it some time back and saw some one pots that i knew to be a good rifleman and a good reloader. He called QL "the birth place of bad ideas!" I didn't think much of it at the time but I have been seeing more and more of these kinds of posts. Maybe he was right.

I think that using QL as one's sole reloading manual is probably a bad idea, but the program is not really designed to be that and provides so much information beyond what the reloading manuals provide that it is, in my opinion, a very good supplementary source. Seeing comparative results with many powders for a particular bullet gives the reloader a ton of information that you just don't get in the reloading manuals--most of which deal with only the one brand of bullet and a very small array of powders. In addition, pressure estimates not found in the manuals is super useful. My go-to process will be to start with QL and then go to several reloading manuals with the QL results to ensure safety.

Ebb, what have you seen portrayed as the shortcomings of QL?

 

[cem]

A proof load is safe for proof but not for sustained use. After sustained use with excessive pressure a rifle will fail with a load that is safe without such sustained fatigue. A given load fired repeatedly will have a range of pressures as measured. SAAMi sets typical pressures such that the maximum pressure in a series will be safe and not stress the action to the point that future low pressure loads will be unsafe.

Bottom line to speak of pressure is really to speak of a range as a pressure series will not always hit the exact same pressure. Cartridges may produce a safe pressure for one firing but an excessive pressure in among the safe pressures for a pressure series. There is plenty of information free from SAAMI and Brownell's series on pressure factors available from Wolfe contains a lot of information that is eternally valid.

"Is there an answer to this question" There may be an answer but there is no simple numerical answer.

Modern production bolt action rifles will in general handle pizeo measured pressures higher than many SAAMi limits that consider the full range of rifles.

In that sense many manuals will have a range of loads for cartridges such as the .45-70 that can properly be used at much higher pressures in a bolt like the Siamese Mauser conversions than in an original trap door Springfield.

The same is true of firearms chambered in .45 Colt. The same is true of firearms with different degrees of support for the cartridge as in the guppy brass in .40 S&W and a myriad of others.

It should be obvious with such examples there is no single value answer for the full range. There may be such an answer for a limited set of strong bolt action rifles with a limited set of cartridges. And a different answer for a limited set of weak actions with the same cartridges. I would not hesitate to be guided by the highest listed pressure for a range of cartridges in the same action I am loading for. That does not mean and don't try this at home that the .45 ACP can be loaded to same max psi as a 9x23 when each is fired in a 1911.

 

[dellet]

I will throw out a an example of SAAMI pressure specs that I know to be a head scratcher until explained.

300 Blackout, same mechanism as 5.56 NATO, just change the barrel. SAMMI pressure is at 55K. Higher pressures cause tuning problems at full auto. To be able to cycle subs/supers with and without a suppressor the ammo specs were gamed so an adjustable gas block was not needed.

The proof load is still same pressure as 5.56 NATO, it's just hard to get it to feed.

There are reasons other than going kaboom to limit pressures.

 

[mikecr]

Problem pressures and safe limits are different animals.
And for all the concerns with QuickLoad, then where is the concern with manuals?
After all, with manuals someone reported from their powders & bullets & barrel combinations. It is just the same with QL. So any source is only a starting consideration. Right?

You follow the golden rule to work up with any changes, and typically you'll hit problem pressures way lower than safe limits.
You gotta stop there and address problems before moving upward. If you're rational you'll know when more isn't worth it. Isn't worth the efforts,, isn't worth the risks.

 

[ebb]

I think it is too complex and requires so much data that many don't give the program all of what it needs to make a good outcome.

 

[Dgd6mm]

Good info in, good info out. You have to understand how to use it Read the manual and adjust accordingly. I haven't had any load issues using it for everything I shoot. It certainly cuts load costs substantially down. It paid for itself quickly in saved components. My rifles shoot very well.

 

[Texas10]

Very rarely will a max load also be the most accurate load. And what's max in my chamber that was cut with an oversized reamer and a long leade, may be dangerously over pressure in your chamber that was cut to a minimum size chamber and no leade. Book values take this into account and then add a healthy fudge factor to account for common mistakes, powder scale errors, and just plain human errors.

 

[918v]

A Remington 700 will explode at 125,000 PSI. Arguing whether 63,000 or 65,000 is safe is silly. The military uses ammo loaded to 70,000 PSI in their Remmy 700 based sniper rifles. That’s 70,000 PSI under sustained use. For all intents and purposes, any book load you slap together is safe to use as long as you stay away from the rifling. All that’s going to fail is the primer pocket.

 

[wagonman]

A Remington 700 will explode at 125,000 PSI. Arguing whether 63,000 or 65,000 is safe is silly. The military uses ammo loaded to 70,000 PSI in their Remmy 700 based sniper rifles. That’s 70,000 PSI under sustained use. For all intents and purposes, any book load you slap together is safe to use as long as you stay away from the rifling. All that’s going to fail is the primer pocket.

well I for one remember loading max out of my speer#10 needing a 2x4 to open the bolt on my rem 700 7 mag learned printed max loads are to be worked up to, learned that one 40 years ago.

 

[918v]

I remember staying away from the lands when loading max loads.

 

[Uncle Ed]

What Are Considered Maximum Safe Pressures in Rifle Cartridges

In a bolt action the limiting factor is the quality and hardness of the brass.

Below this photo is from this reloading forum and the poster said he increased the load until he got brass to flow into the ejector. He then said he backed the load off 1 or 2 grains and knew the elastic limits of the brass. The photo is Lapua brass and softer brands would not take as much pressure.

Below Lake City brass uses a harder brass that can take more pressure and not deform.

 

[SBS]

"In a bolt action the limiting factor is the quality and hardness of the brass" (quoted above)

Absolutely. Modern actions will take much more than the brass; those that are wrecked by overloads are because of failed brass and the resulting escaped gas.

 

[Zero333]

The problem with CIP and SAAMI PSI ratings is they are not tested at the same locations of the brass/chamber. Thus they can't be directly correlated with a simple mathematical formula.
We would need to know the type of steel the testing receiver is made of. It's tensile strengths, it's thickness, it's temperature etc.. etc. and the same about the brass and it's structure etc.. etc... to come up with a proper conversion formula.

In the end, it's our job to test the rifle and the load.