QuickLoad Maximum Pressures

[TonyR]

Have any QuickLoad users experimented with loads QL predicts to exceed the maximum pressure rated for the case? And, has anyone compared the pressure estimates from QuickLoad with the readings from one of the pressure sensors like and Oehler 43 or the RSI?
I have been using QuickLoad for the past year and have found it to predict velocities very precisely for my rifles, usually within 1% if I use a good chronograph. Since I purchased the program, I have not tested any loads predicted by QL to exceed the maximum rated pressure of the case, but I have analyzed loads that I developed prior to purchasing the program and found that they are estimated to exceed the rated pressure, in some cases substantially. None of these loads have shown any of the usual pressure signs and case life has been fine. Anyone have any thoughts about this?
Thanks

 

[scout1]

Tony, I have just about the same experience. Before I purchased Q.L. I was running Benchmark and the 155 Scenars pretty hot at around 2950 fps out of a 26' barrel. Now that I can see the pressure curves and heat of explotion mixed in with start pressures and chamber pressures I have backed off a little. It has definetly saved me the purchase price in time and componets including barrel life twice over allready. Buying matched lots of powder and callibrating the program to that powder and saving the file is as useful a tool as I have found anywhere.

 

[TonyR]

Hi Jon.
I agree completely about the value of the program. I recently rebarreled two rifles based on QL data and I have had no reason to regret my decisions. I could have figured most of what I learned by trial and error, but I believe that I got an excellent solution with a minimum of time and expense.
It seems likely that the QL pressure curves would have to be very close to the real thing or the velocity estimates would be way off,I'd like to hear about some comparisons with actual pressure measurements.); but I guess what I'm also looking for is what 'maximum pressure' really means. For example, does it mean the safe maximum, with a safety factor built in, for cartridges made with brass and other components from any supplier loaded in any rifle with a CIP or SAAMI spec chamber ? Or is it the maximum different for an all custom single shot bolt rifle from a top gunsmith using Lapua brass resized and loaded with dies custom made for the chamber?
I have no intention of loading anything above the max rated pressure, but the discussion about xdeano's 308 Win made me wonder about this.

 

[Forum Boss]

Some tips that will help you get more precise results from QuickLoad:

1. You need to measure the actual capacity of your fired cases. This can make a big difference in pressure.

2. QuickLoad says to add 7200 psi to the default start pressure when you seat the bullets in the lands. I've found that, with small and medium-sized match cartridges, this is excessive. I use 6000 psi (vs. 3626 default) as 'in the lands' start pressure for a 6BR and this seems to produce a better correlation with observed pressures and recorded velocities.

3. Remember there are significant lot to lot variations in pressure, and barrels can be very different. Just compare the ADI powder data with the Hodgdon data, for the equivalent powders) and you'll see up to 3000 psi difference in predicted pressures... supposedly for the same propellant with a different name. Go figure.

 

[Chas]

Quickload is a fantastic tool, I highly recommend it to to reloaders.

 

[Doom]

but I have analyzed loads that I developed prior to purchasing the program and found that they are estimated to exceed the rated pressure, in some cases substantially. None of these loads have shown any of the usual pressure signs and case life has been fine. Anyone have any thoughts about this?

There is a common misunderstanding about rated pressure for ammunition and pressure signs from components. For instance the 6.5 Creedmoor uses a LR primer and has a Maximum Average Pressure (SAAMI/CIP) of 65,000 psi while the 257 Roberts uses the LR primer with a Maximum Average Pressure of 54,000 psi. If looking at primer deformation we would not expect to see that LR primer to show deformation below 65,000 psi. Is there a calibration for degree of primer deformation based on pressure? About all we know is when the pressure gets high enough the primer begins to show signs that it is at its limits. It doesn't tell us what the pressure in the case/chamber is.

Similarly we have no real gauge for things like case head expansion or ejector swipe. We know that when the brass flows the pressure is at or above the limits of the brass. Unfortunately we do not know the actual yield/tensile strengths of the material so we do not know what pressure this occurs at. We assume it is above the Maximum Average Pressure but we know nothing of actual pressure.

Hard bolt lift or hard extraction occurs when the case and chamber expand beyond the point where the case returns to a dimension greater than the chamber when the pressure returns to normal atmospheric pressure. As pressure builds the case expands to fill the chamber and then the case and chamber expand as full pressure is achieved. At that pressure the case has expanded due to stress exceeding the yield strength of the case and the chamber expanded elastically (stress less than yield). The result is the chamber returns to its original dimensions. However, since the cases exceeded its yield it will not return to its original size. If the combination of the two expanded beyond a certain point, the case will not return to a dimension less than the chamber and will experience what is in effect an interference fit. We assume this pressure is above the the Maximum Average Pressure but again have no idea what that pressure is.

When we see these "signs" we rightly assume we are overpressure, but the lack of these signs in no way guarantees that we are below Maximum Average Pressure as defined by SAAMI/CIP. In the absence of these effects we assume we should be able to safely utilize the ammunition and firearm since the individual components do not appear to exceed their safe capability.

 

[Zero333]

There are so many variables the best thing anyone can do is measure the actual velocity and adjust QL parameters to match.
Otherwise it's no different than any other reloading manual... REDUCE and work UP accordingly.

 

[gunsandgunsmithing]

I always appreciate the data but I honestly thought that posting QL data was frowned upon on here.

 

[mikecr]

I don't think QL data should be posted on forums.
I think people should support the software offering.

 

[CharlieNC]

I purchased QL years ago and have found it to be very useful. A year ago I downloaded the free Gordon Reloading Tool, and found it to be more comprehensive and it included profiles for additional powders missing from QL. Interestingly while the results generally agree, pressures from GRT are often a bit lower but I have not attempted to diagnose why. For real world calibration GRT also includes user feedback results including velocity, don't know about any pressure info.

 

[dcali]

I'm not a fan of people posting data either. At least not without some other context. Discussing features or results is one thing. Just saying "hey can someone run this for me so I don't have to buy it" is another.

I'm also not a fan of the dreadful state of both QuickLOAD and GRT. Both are awful software. QuickLOAD is about 30 years behind the times.

GRT is a mess that they should open source if they're not going to charge for it in my opinion. At least then someone could take the code and make a proper web application out of it. If they just worked on the underlying internal ballistics engine and made it available, I'm sure people would take it and make all kinds of cool stuff with it. I don't get why they're wasting time and resources on features that aren't terribly useful and have been done a million times elsewhere.

 

[Doom]

I'm not a fan of people posting data either. At least not without some other context. Discussing features or results is one thing. Just saying "hey can someone run this for me so I don't have to buy it" is another.

I'm also not a fan of the dreadful state of both QuickLOAD and GRT. Both are awful software. QuickLOAD is about 30 years behind the times.

GRT is a mess that they should open source if they're not going to charge for it in my opinion. At least then someone could take the code and make a proper web application out of it. If they just worked on the underlying internal ballistics engine and made it available, I'm sure people would take it and make all kinds of cool stuff with it. I don't get why they're wasting time and resources on features that aren't terribly useful and have been done a million times elsewhere.

GRT has current issues since the death of Gordan. Currently they are forming a group to continue the development. What becomes of it we will have to wait and see.

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[CharlieNC]

What am I misssing, I just used GRT again with no problems?

 

[RegionRat]

Just FYI. The thread was from 2009 and the OP hasn't been seen since 2016. Not much point to directing comments at them. Might be worth starting a new discussion point for those who are still around....

Maybe the accuracy of the models? Or, the philosophy of posting QL/GRT answers? YMMV

 

[SeabeeKen]

There is a new GRT expected to be released in 2025. I think you'll see some interesting improvements. I'm looking forward to it. GRT does a lot more than QL

 

[Doom]

Just FYI. The thread was from 2009 and the OP hasn't been seen since 2016. Not much point to directing comments at them. Might be worth starting a new discussion point for those who are still around....

Maybe the accuracy of the models? Or, the philosophy of posting QL/GRT answers? YMMV

Yep. I actually replied because of the title and a question that came up recently at the range related to reading primers on a pistol round that lead to a whole discussion similar to my post.

 

[RegionRat]

Yep. I actually replied because of the title and a question that came up recently at the range related to reading primers on a pistol round that lead to a whole discussion similar to my post.

Keep or pitch, you may have already seen this one.

Merry Christmas

 

[Doom]

Keep or pitch, you may have already seen this one.

Merry Christmas

Actually read this about 10 -12 years ago.

 

[Doom]

Interesting analysis if anyone is interested.

 

[RegionRat]

Certainly good enough answers for starters.

Those were what we called "back of the envelope" calculations, or, if we were sitting at the bar they were "back of the napkin"....

Several significant inventions were born on the back of a napkin at Petrelli's in Culver City. We later had a few of them mounted on plaques and displayed in the office along with the formal patent application drawings.