Chris 
I use about 18 Grains of 4227 with a wad placed .100" off the powder. It is a fairly mild load and shoots acurately. The wad off the powder does two things; first if the wad seater dosen't go all the way to the shoulder then I have put in too much powder. Second having it off the powder insures that I won't ring the barrel.

40 Rod

After over 50 years of shooting black powder cartridge rifles, I am of the opinion that black powder cartridges are just that - - - black powder cartridges.  I've tried various smokless loads over the years, but they never worked as well as black powder.   If you want to shoot smokless powder, get a rifle chambered for a smokless powder round.  Shiloh offers the 30-40 Krag, 38-55, and 45-70 for which smokless powder ammunition is available.  If you read the fine print in their catelog and manuals (?what read?),  I think you will find a statment to the effect that their rifles are not warrented for smokless powder except for those chambings which are currently being loaded.  Well, at least their manuals used to say that.   

Aside from the dangers of double charges, what really soured me on smokless loads was their dismal performance in cold weather.  In that particular case I was using 3031 in a 45-70.  Shot really great in the summer and I had planned that as a hunting load.  Tried it at about 10'F and it gave 50 yard shotgun patterns.  Any safe loading of smokless in a black powder cartridge is operating at the bottom end of the pressure curve.  Lower the temperature, and you are not developing sufficient pressure for proper combustion.  Result, lousy accuracy.

If you insist on usng smokless powder, get a rifle chambered for a short case - -like the 40-50 or something like that.  If you want a smokless powder loading for the 40-70 SS, get yourself a suitable rifle chambered for the 405 Winchester.  A High Wall or Ruger comes to mind.

Keep your powder dry,
George
Salmon, Idaho

I only use smokeless in my Shiloh Sharps rifles, and am aware of what Shiloh's recommendations are.  But to add fuel to the fire, Kirk has said on multiple occasions that the Shiloh Sharps is as strong as a Ruger #1, so I don't think that the barrel, or action, are limited to black powder pressures. I know they advise against smokeless in the larger cases. 

Interestingly, in one of the older issues of SPG's magazine, there is mention of  Shiloh Sharps in .45-90 shooting a 250 on the German Ring target with smokeless!  I believe it has been repeated, so it's not a fluke.  I shoot a lot of black powder, and really enjoy it, but have never heard of anyone shooting 250's with it in a .45-90.

Chris.

Been shooting a couple of 40-65 for 20 some years now.  Got a 40-70SS some months back.    Shot them with black and smokeless, in good weather and cold both.

They've been chronographed a lot, often beside modern cartridges from 221 Fireball up to 45 caliber.    The 40-65 and 40-70SS haven't acted differently than the modern ones with smokeless when hot or cold.   And that's been proved by the chrono.    

Some smokeless is temp sensitive.  Some isn't.  Whatever the cartridge.   

I don't use powder that shows me any temperature sensitivity.  Shooting year round it isn't a real bright thing to do when shooting in bad weather happens mostly in matches.  

There are a number of smokeless powders that give excellent performance in originally black cartridges at original velocities.   Loading my 40s to black velocities is quite easy.   5744 has proven to be excellent at giving black velocity consistency as well.  Single digit SD is normal and usually slightly better than the black I've been able to find.   It's a double base powder which just may be the reason it gives such good and consistent ignition.   It fills the case more than half full, so double charges aren't in the picture.   I've also had good results using AA8700 which definitely fills the case more than half full.   And a couple others, but have stuck with 5744.  

Black wasn't sold around here within a couple hours drive except in on place, while Pyrodex and later some of the others were available at dozens of shops.   So I shot mostly subs when I wanted smoke.   Turned out getting original black velocity was easiest with 5744.   
    

George, 
That barrel and action kicked around the office for many years! If I recall correctly The barreled action was fired several times with compressed charges of IMR 3031, with no damage other than the primers disappearing out through the vent hole at the bottom of the breech block. The barreled action was then fired with the same load, but with two 500 grain bullets pounded into the bore with some spaces left between them. Several of these loads were fired with no damage to barrel or action. Finally the triple ball load was fired with the barrel chrushed .025 in a very heavy mill vise. That procedure produced the barreled action we remember. I have always wondered what H.P.White's would have estimated the pressure for THAT one  . 
   However... Like George stated, the large capacity case with a small smokeless powder charge (and some advice from the company legal dept.) was the reason for the cautionary warning.
Best regards,
Tom W.

Sure, you can get good accuracy with smokless powder sometimes, even with the long cartridges.  I wouldn't question that.  But, why bother.  If you want to shoot smokeless powder, get your rifle chambered for a short case and avoid all the inherrent problems of short charges in long cases.  Might save you a block through your forehead; or a ruined hand.  I'd rather clean my 40-70SS a thousand times than loose the use of my left hand.

I don't know what the pressures were with the intentionally "blown" Shiloh I mentioned earlier.  They had to have been pretty darn high.  Wolfgange Droege told me that the only real product liability insurance was to build an indistructable rifle.  He also told me what the A.P. White labs had successfully tested the Shiloh to, but I will honor my promise to him tothat I would  never reveal it.

George

Bravo, 40-Rod!! Can't be too safe, in this and other things as well.