Chuck said
Mike I have no idea what will happen next.  All I want to do is get up to the factory speed. 
  

I'd be pretty tickled with anything within a hundred FPS. 

Mike

Mike

In the optimal range for an appropriate powder in a given cartridge and moving in very small increments during your ladder test the change may appear to be linear for that narrow range but at the lower end the velocities and pressures are erratic (as you experienced) and in many situations the pressures at the upper end can get dangerous in a hurry. That's why I am quite certain the pressure changes are not linear. I'm pretty sure you know that. Your adventures with these big BP cases are interesting and I think you may just be able to pull it off. 

Mike

Bert H. said

The proof will be in what the final powder charge is that is required to duplicate the factory load (velocity)... I am willing to bet that it will not be just a mere 32 grains of IMR 4198 in a 40 Express cartridge.
  

Exactly.  We'll see.  I plan to up the powder.  I will load some at 31 grs and then 32.  I need to figure out what caused the one last time shoot so low while my first shot was around 1200 fps.?

Chuck said
We both know the 40% rule was used at least 75 years ago, maybe before.  It does work for some large calibers like the 45-70.  It does not work for everything. 
https://grokipedia.com/page/frank_c_barnes
Read all of it.  
  

The proof will be in what the final powder charge is that is required to duplicate the factory load (velocity)... I am willing to bet that it will not be just a mere 32 grains of IMR 4198 in a 40 Express cartridge.

https://grokipedia.com/page/frank_c_barnes

Read all of it.  

Chuck said
First, I'd like to see Dupont's data and the manual you are quoting from.   Why don't we try some of your loads.  Lets pick one of your rifles and load it with 4198 and 4 grains over the Documented load requirement.  Totally unsafe. 

Chuck,

Again, where did Barnes get his load information from ?? He most certainly was not a ballistics expert.  Are you certain his published information is correct ? I most certainly am not of that belief.  Further I without any hesitation would load a 40 Express cartridge with 36 grains of IMR 4198 and then shoot it in an original high-wall rifle and think nothing of it.  All of that stated, you need to do what you decide is reasonable. Let us know what 4198 load you eventually land on that equals the original factory load.

Bert

p.s. I load 38-55 cartridges with 26 grains of IMR 4198 under a 245 grain .379 cast bullet and shoot them in my high-wall. 

Chuck said

Bert H. said
I am not advocating loading excessive loads... simply a grain or two above the minimum recommend load, and nothing less than minimum.  Intentionally loading under the minimum recommended load will cause erratic pressure & velocity.
  

The problem is there is no recommended load data for the EX calibers.  Actually that is true for the majority of our old calibers.  If anyone has some reputable data I'd love to see it.  Cartridges of the World by Frank Barnes is the only source I know of that has data for all of our old calibers.  But, it is usually just one load per bullet weight and the Factory black powder load. 
I did get one erratic shot for the 2 that fired.  Both were using the same 30 grains of powder and the same cotton plug to keep the powder up against the primer. 
  

I have no idea where Barnes got his information for the 40 Express cartridge, but using Dupont's (old) published information, the 40 Express (40-110) can safely be loaded with 44 grains of IMR 4198 (40%).  At just 30 grains, you are at just 27%.  In your shoes, I would bump it up to at least 36 grains as a starting load.

TXGunNut said
Chuck-
The problem with Butler's ratios is that the relationship between powder and pressure and velocity changes based on case volume, case shape, bullet weight, temperature and other factors. That ratio will probably work for one cartridge and one bullet but will be affected by other factors. My reloading mentor years ago told me smokeless powder is not linear in behavior and I'm glad he got that into my thick head over 40 years ago. For quite a few of the cartridges I like there seems to be a constant relationship between BP and 4198 but in many of those cartridges BP will outperform 4198. IMHO smokeless powder did not and never will replace Holy Black. Smokeless powder ushered in a whole new class of cartridges and is pretty awesome stuff. BP cartridges in BP-era rifles will always perform best with Holy Black, again IMHO. I have my fun with smokeless in BP cartridges but it's very hard to beat Holy Black. Many good BPCR loads have single-digit SD"s, lots of very good smokeless loads can't do that. I'm hoping to shoot a few BP 45 Colt loads this weekend, there are some excellent smokeless loads for this cartridge but few things put a grin on my face like the boom of a BP load in a SAA (replica!). 
 
Mike
  

True, but the modern powder will always have the ability to create more pressure and it doesn't take much to make a big change.  There is a reason I use BP to fire form the cases.  It is easier to control the outcome.  As far as smokeless powder not being linear, that's not the case.  In my modern rifles I always do a powder ladder test.  I pick a starting load and then go up .3 grains for about 3 grains.  Each .3 grain load goes up about the same fps.  Single digit ES' is not hard to get when you have a good load.  In my case I shoot 5 round groups when doing load development.  All it take is an ES of 20 to get a single digit SD.  Play with this. The number of shots makes a big difference.  10 shots with an ES of 20 will be a lower SD than the 5 shots. 

https://www.calculator.net/standard-deviation-calculator.html

Thanks, Don

Bert H. said

I am not advocating loading excessive loads... simply a grain or two above the minimum recommend load, and nothing less than minimum.  Intentionally loading under the minimum recommended load will cause erratic pressure & velocity.
  

The problem is there is no recommended load data for the EX calibers.  Actually that is true for the majority of our old calibers.  If anyone has some reputable data I'd love to see it.  Cartridges of the World by Frank Barnes is the only source I know of that has data for all of our old calibers.  But, it is usually just one load per bullet weight and the Factory black powder load. 

I did get one erratic shot for the 2 that fired.  Both were using the same 30 grains of powder and the same cotton plug to keep the powder up against the primer. 

The problem with Butler's ratios is that the relationship between powder and pressure and velocity changes based on case volume, case shape, bullet weight, temperature and other factors. That ratio will probably work for one cartridge and one bullet but will be affected by other factors. My reloading mentor years ago told me smokeless powder is not linear in behavior and I'm glad he got that into my thick head over 40 years ago. For quite a few of the cartridges I like there seems to be a constant relationship between BP and 4198 but in many of those cartridges BP will outperform 4198. IMHO smokeless powder did not and never will replace Holy Black. Smokeless powder ushered in a whole new class of cartridges and is pretty awesome stuff. BP cartridges in BP-era rifles will always perform best with Holy Black, again IMHO. I have my fun with smokeless in BP cartridges but it's very hard to beat Holy Black. Many good BPCR loads have single-digit SD"s, lots of very good smokeless loads can't do that. I'm hoping to shoot a few BP 45 Colt loads this weekend, there are some excellent smokeless loads for this cartridge but few things put a grin on my face like the boom of a BP load in a SAA (replica!). 

Mike

Chuck said

Bert H. said
Chuck,
that high-wall frame will safely handle way more pressure than you will ever subject it to with the IMR 4198 loads you are using.  Due to its burn rate and burn characteristics, you would have to load it to nearly 200% before any worry about the pressure causing any safety issues.
Bert
  

I am aware of how strong the action is but there is no safe reason to push it passed the factory loads.  This rifle is 136 years old and one of the rarer rifles that I have.  I have no idea how it was treated in the past but I do know I'm not going to abuse it.  I plan to at least work it up to around the 1,600 fps range no matter what the powder charge might be. 
I recently read, in the Win 1873/1876 book by David Butler, where he shows results of a test that figured energy per grain of powder for the 45-75 and a 308.  Not a lot of data but the end result was the 75 grains of black powder generated 1,485 psi of muzzle energy for 20 psi per grain and 47 grains of the the unknown smokeless powder generated 2,730 psi muzzle energy or 58 psi per grain.  That's almost 2x difference in muzzle pressure. 
If any of you don't have this book, don't pay much for it.  It does list the cartridges on the 1874 cartridge board.  All rimfire except the 44 WCF.
  

I am not advocating loading excessive loads... simply a grain or two above the minimum recommend load, and nothing less than minimum.  Intentionally loading under the minimum recommended load will cause erratic pressure & velocity.