Curt, I would lean toward the 40-65 wcf  as brass and dies are easily obtainable. Using smokeless would allow velocities to reach out and still hit with authority. I would also consider the 38/56 wcf as recoil is even less. I have taken a mule deer with the 38/56 RB that you installed a limit screw on the extractor and plan on using it for an elk hunt soon.  I am getting 2100 fps with a jacketed Horn day 270 gr  round nose. My 40-70 SS Hepburn kicks like a mule with 360 yr PP bullets at 1800 fps but it would be a good choice if brass was more available and dies were more standardized. It is really pleasant to shoot at 1300 fps.  The 40-50 would be my choice over the longer 40-70 and 30-40 brass is readily available. The case diameter is less than the 40/70 BN so would result in less thrust.  My Borchard 30/40 Krag Improved that you built has killed elk with the 200 gr  Nosler  Partition and recoil is nothing even with the light barrel you installed. The older I get the less I like recoil!  Tom

Thanks for the responses. The 40-65 has always been a great choice and fills most requirements. A friend was asking my advise, I suggested the 40-65 or 40-60 Maynard as cases for the Maynard are easy to form. I suggested he contact Borchardt Rifle for his project. The certainly have a lot of experience working on the Borchardt.

The .40-60 Maynard is a slight bit more accurate but the cases and dies for the .40-65 WCF is definitely much more available. 
It is getting much more difficult to find .30-40 Krag cases to make into .40-60 Maynard.

I did one in 38-72. Good round except for the high cost of brass and dies. Have to make them from 405 win and we all know how pricey that stuff is now. I have a small fortune in components but I have them now and the brass should last a good long time. 



JMH

I used 40-65 for many years in competition but for hunting I liked the 40-90 BN.