OTOH it's hard to beat Holy Black! I dug out a Cimmaron SAA clone and some 45 Colt BP and cast loads to let Jeremy P help me shoot today. Nothing like a big boom and cloud of blue smoke! It's a bit of a handful but now Jeremy understands why the 45 Colt was held in such high regard 150 years ago. Some of us still think it's pretty special.

Sorry to hear about your friend, Chuck. Hurts to lose a fine old rifle but we all know he was lucky. 

Mike

1. 25-20 Single Shot (should have been called the 25-19) - 10.5 grains (52.5%)

2. 32-40 - 18 grains (45%)

3. 38-55 - 24 grains (43.6%)

4. 40-70 Ballard and 40-70 Sharps Straight - 28 grains (40%)

I have yet to find an older (original BP) cartridge that exceeds the original BP velocity when loaded with IMR 4198 using the 40% rule of thumb.

As a side note, I also load my 222 Rem Mag with 4198 (25.0 grains under a 35 grain V-Max), and used 34.0 grains when I loaded for 33 WCF.

Once again, each person must choose their own loading information.

Bert

In the 1890's Winchester used the Dupont #1 and #2 smokeless powders.  The #1 was similar to 4198 and is for large calibers like the 45-70.  The #2 was used for the smaller calibers like the 44 WCF and was similar to 4227.  Winchester started their development of smokeless powders in 1893.  They started selling smokeless powder cartridges in 1894.  After 1900 Dupont switched to Shapshooter which is faster than 2400.  It is between Blue Dot and 2400.

So the 40% rule was started just before 1900.  I'm not sure when the Lyman ballistic lab did some tests comparing BP and 4198 in the 45-70.  But in one test they used a 420 gr. bullet and 28.5 grains of 4198 and the same weight bullet and 70 grains of black powder. 

BP-1,268 fps and 16,400 cup

4198 - 1,267 fps and 13,900 cup.

I load at least 10 Winchester calibers using 4198.  The 40% rule does not always work.  I don't have the answer but things are different today than it was in 1900.  Our modern cases don't have the same case volume.  Try putting the old volume of BP in a modern case.  A lot of time it has to be compressed.  Since I have never fired a round, that I loaded, without the use of a chronograph I know the modern powders are hotter.  Another reason to start low and work up. 

If John Cort was still alive he might have had the answers?

A bit off the subject but is safety related.  My friends shoot every Wednesday.  This past Wednesday one of their friends was shooting a pre 64 Model 70 in 270.  He totally disintegrated the rifle. Luckily he only got his face burned.  He used the wrong powder.  Be safe. 

TXGunNut said

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
  

 Me too.  

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