An experiment in .40-65

Among the things I've learned about this cartridge:

Starline makes brass for it.  Works great in leverguns from what I'm told, but in most single-shots it tends to wind up, after fireforming, shorter than the standard minimum(same as .45-70, 2.095").  I've read they make it as they do to fit in Shiloh rifles with tight chambers, so in anything larger, too much shrinkage.

 

Using Starline .45-70 cases, what I've done is anneal the case, use a .40-65 size die to form them(the right amount of lube and just a bit at a time to avoid wrinkles).  Then trim to 2.138", which will fully chamber in the rifle in question.  At that point it's time to fireform.

 

Which is easy enough: load the cartridge and shoot it.  The pressure and heat forms it to the chamber, and in doing so causes it to shrink a touch in length; these have consistently come out 2.125".  I've had some people tell me fireforming isn't needed, but I tried using new-formed cases with a standard load and accuracy definitely suffers.  So I've been using a 300-grain cast bullet over some A5744.  Which works well, and I use it for shorter-range offhand practice, but since I've had to make the alloy for the bullets I wondered if I could use a lighter bullet for this purpose.

 

Problem: finding data.  The lightest bullet I could find anything for is 300 grains.  Asking around found a number of people who'd tried it using a .41 Magnum bullet(both cast and jacketed) in rifles with a .408-.409 bore, some with success for shorter ranges, but nobody wanted to name a powder and charge.  So more digging was done, and I settled on trying a 200-grain semi-wadcutter(because I have those from this mould*) over 19.0 of A5744 in five new cases.

That shot nicely, light recoil and(for a quick try at an indoor range) decent accuracy, and the cases measured the same length after firing as those with the 300-grain bullets and full loads.  A couple of the cases showed light streaks of fouling, indicating pressure was low enough that the case wasn't expanding enough to fully seal the chamber.  So I decided to bump it up to 19.5 grains.  Which gave this result at 30 yards

Not bad, and no streaks on the cases.  With a better rest(I can use all the help possible)I think that might've been tighter.  And if not, it's still quite good for a short-distance practice and fireforming load.  I do want to shoot this over the Chrony and see what velocity it's giving.

*That bullet shoots very well with light loads in the .41 Mag revolver I've tried it in