Out of curiosity I compared the pressure curves for 4227, AA#9,  and 4100 in Quickload, using the .25-20 SS cartridge model.   QL has no data for 4759.

They all reach peak pressure at the same time, 0.5 milliseconds, given loads for equal pressure..(~12,800 psi).   

4227 appears to have a tiny bit of a "fat tail" to the curve, by comparison, which nets about 40 fps more velocity for the same peak pressure, calculated for a 24 inch barrel.  

Maybe I can figure out tonight how to get the comparison into a single graph.

4759 or 4227 I have found differences lot to lot with either powder so close one lot of 4227 will be hotter than 4759 grain for grain, another lot the reverse,

This observation by strike on target same sight settings. Of course other factors could have produced the result. Ambient temp for example

Still they are very close

Boats

oneatatime wrote on Sep 1^st, 2017 at 7:15pm:


Well, the examples I cited all calculated to 1390 fps from a 24 inch barrel, give or take 10 fps or so.  (Within the error budget of the model, I would think.)  

You have a point, however.  Powders much too fast for a given application will produce higher peak pressure when loaded to a chosen velocity.   

Unique, loaded in the model to 1390 fps, calculates to a bit over 21,000 psi.  Red Dot is even worse.  I want to guess that this is related to the total volume of gas evolved.  The pressure curve for these powders falls off dramatically faster than the 4227 family.  (If I remember my integral calculus right, the velocity would relate directly to the area under the curve, assuming you ignore friction losses.) 

But 2400, again loaded to 1390 fps, calculates to 12,900 psi.  

This is why I feel that the Government should be required to issue a copy of Quickload to every reloader at taxpayers' expense.!       I never look at paper manuals anymore.  And since you can create your own cartridges, it's perfect for our old crocks for which loading manuals never even existed.
 
Funny thing, by the time I needed to use calculus for engineering problems, there were computers to do it for me.  Later on I made extensive use of a function called the Fourier Transform, which I could not write a proof for to save my life, but no matter, just load the data into the software and push the button!  I don't have a clue how Quickload's model works, either.  But it does.  It's never been far off when I get to the range. Usually a bit on the conservative side, so I wind up tweaking the load up, not down.  It even made a fairly accurate velocity calculation for when I fired a double charge of AA#9 across the Chrony once upon a time. 

4100 when loaded to appropriate levels is perfectly safe for a 25-20 i have shot it in a SDtevens 44 1/2 with no sticking or other problems.

40 Rod

A 25-20 load that starts sticking in a Stevens 44 has gone well beyond the clear the range point in my book. Unfair to compare it to a 44 1/2.

Also, the 2520 head area is small for lower backthrust on breechblock
beltfed/arnie

lars wrote on Sep 7^th, 2017 at 5:35pm:


Not I, but I'll report that in my experience Lil'Gun wants a little more pressure than that to be consistent.  Above 20,000 psi.  Not knocking it - it's wizard in the Hornet.

To all. I use 4759 exclusively in all my SS Rifles for one reason. In the Calibers I prefer. 32-40, 33-40,38-55. You cannot throw a double charge. Most of my loads when doubled over flow the case. Hard to miss. And even in the large caliber
calibers they either do over flow or are so close to the top of the case you cannot properly load a bullet in them. Now I do not claim that 4759 is the BEST? for accuracy. But for most of my Rifles a load can be found that shows really good accuracy.
My shooting efforts have for the most part been offhand. Have started to lose that edge but still enjoy it. Holding up a 14 to 18
Lb. Rifle stresses me now. May have to start Bench shooting in order to keep active. At least I will have some rifles that can become bench rifles. Just my thoughts. Regards, FITZ-G.