I shot 8 grains of unique in a cast frame Ballard 44/40 with a 200 grain bullet with no problems. It is a very mild load with a trajectory similar to a 22 Long Rifle. I've never chronographed it and don't know the velocity.

OK, I've figured it out ...
* the maximum pressure for a 44-40 per SAAMI is 13,000 cup
* JM Marlin cast action rifles were chambered for 44 rimfires (44 Henry)
*  If the cast receiver was strong enough for the 44 Henry, then any 44-40 reload of any bullet weight that doesn't exceed 44 Henry fps/psi would be a safe reload.
Here is the spec's on a 44 Henry:
Ballistic performance
Bullet weight/type      Velocity      Energy
200 gr (13 g) lead      1,125 ft/s (343 m/s)      568 ft·lbf (770 J)

So any 44-40 smokeless reload equal to or less than 44 Henry ballistics is safe.  Plus the 44-40 black powder fps for a 200gr bullet is 1018 - another safe reload charge

Deadeye, I under stand what you posted but had to do some more reading to get a better understanding.  If I got it right the bolt distance & web thickness are also factors in the amount of back thrust

Vall, thanks for the clarification that the 44 rimfire was the 44 Long Ballard, not the 44 Henry.  There seems to be some details lacking in the reference books about the 44's - "44 Colt and 44 Winchester" for the No 2.  Then in an 1882 Ballard catalog, it lists the calibers as "44 rimless and 44 Winchester"

The 44 rimfire would be a 44 Long - the 44 Winchester would be the centerfire.  The 44 Long was a centerfire and a rimfire round as advertised in a 1876 catalog page of James Bown & Son.  There was also a 44 R.M. "Remington. Marlin" centerfire listed but no reference to Winchester's 44-40

44 Long Ballard
introduced in c.1876 for the J.M. Marlin Ballard Sporting Rifle No. 2, its 227 grain bullet and 35 grain powder charge gave revolver-level performance, and it was really a centrefire version of the .44 Rimfire.[/u] It did not achieve popularity, and was superceded by the .44 Extra Long Ballard, but both were rapidly eclipsed by the .44/40 Winchester cartridge.
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I'm presuming the reference to ".44 Rimfire" was the 44 Henry
Could not find the velocity for the black powder 44 Long cartridge.  
Did find the Extra Long data to be: a 265gr bullet - 50gr of Fg powder with a velocity of 1320 fps

I feel to be in 'safe haven' shooting 44-40 smokeless reloads with a BP velocity less than the 44 Henry of 1150 fps.  The black powder 44-40 was loaded with a 200gr bullet - 39gr FFFg @ 1180 fps ... both less than the velocity of the Extra Long

flyer ... stick with what Vall posts.  He is the old professor and I'm just a wet behind the ears student burying myself in the reference books to learn and try to get a passing grade 

A cartridge collector of renown is John Kort, 44WCF, who doesn't post much here.  John not only collects rounds, he dissects them for inside the cases identification and then shoot them.  John is a true historian because he then prepares reloads - shoots them to match original specifications and then posts the targets
Read this thread from John, My 44-40 Black Powder Journey ... (You need to Login or Register to view media files and links)
It's a shame though, he is not into the calibers for Stevens & Ballards

The thing that has alway stuck in my mind, regarding the 44/40, is the story Ned Roberts told of a bear hunt with his uncle.

Ned shoot the bear numerous times with his new 44/40 lever action rifle and could't put it down. His uncle shot it once with his conical bullet, MLer and saved Ned.

Frank

By the way, my only 44-40 was a Colt SA that I traded for one in .45. Which brings it's own loading dilemmas.  Brass was tough to get back then for the WCF round except for ancient stuff. I think it's part of why so many of those things got a .44spl. cylinder put in.