All good questions that I too would like to see answers to.  As of about a week now I am shooting a 25-20 SS. I have been shooting a 25-20 WCF for many years but neither in any kind of competition. I seek loads more in line with hunting small game and pests.
One thing I can say about the two cartridges is that I believe the 25-20 WCF has been loaded to far higher pressures that what seems acceptable for the SS. That is pretty easy to see in you look at suggested loads and velocities for both cartridges using the same bullet weights.
I load the Lyman # 257420 bullet to well over 2000 fps for a Winchester model 1892 rifle in WCF but the highest velocity loads I have found with that bullet for the SS max out at about 1600 fps.
I have a Stevens model 44 that has been sleeved to the WCF but I will set a velocity limit in that rifle at about 1500 fps with the same bullet and maybe better to stay around 1300 fps.
  It depends on the launch platform on what chamber pressures should be.  Consider that I load a 2-R Lovell in a model 70 Winchester to about 3200 fps with a 50 grain jacketed bullet using the very same Jamison 25-20 SS brass. The model 70 is about a 60,000 psi launch platform where as even the strongest of the original Stevens rifles the model 44 1/2 falls well short of that limit by about 30%. I think if the 25-20 SS was chambered in something of similar strength as the Model 70 Win then it could move to a different class of cartridge somewhat similar to the 25 Copperhead in ballistic performance.

I shoot with quarter bore guys, and some are looking at switching from the wcf  to 25-35, main reason is the case is longer, so less issues with dumping loose powder in the action. I have seen the guys shooting jn the high 240's, and a couple 250's i think. I was advised to stay away from the 25-20 SS for 2 main reasons, brass availability,  and barrel twists. The original rifles in the SS were slower twists, so you have to keep the bullet weight down. The WCF is easy to get chambered in a 1:10 and shoot heavier.

If you are building from scratch, and have the brass, i don't know that there would be a detriment to building a fast twist SS

Thanks guys I'm thinking

Rick

Nineteen 250 QB targets shot with a 25-20 WCF in the last 13 years. Rifle is a CPA with a Douglas 10 twist barrel. A Mos 120 gr. bullet at ~1650 fps breech seated works. R-P brass is absolutely required. 

Eighteen were shot at 200 yards, with one shot at 100 yards. 

The one I am most proud of is the 200 yard Iron Sight 250 target. 

I also have scored 1240 out of 1250 twice in a 50 shot match with the same rifle. You need to average 248 for five targets to score 1240.

So,yes, the 25-20WCF is a competitive cartridge and will give you excellent results, if you commit to constant trigger time. 

When I was in my prime I was shooting two matches a month and 3 to 4 practice days between matches. Now it's just match day and I'm happy to shoot a 246 or 247. 

Factory loads in 25-20 WIN are too “hot” for some of the old 25-20 SS.

CHRIS

25-20wcf vs 25-20SS - - brass, twist, pressure vs the "Oooooooooo" factor.

Steve and JerryH talking pressure and I'm listening since that is almost always the make or break element with old SS's and most newer firearms. So let me step into your brains for a minute and ask what are reasonable workable pressures for an old model 44. Though I positively lack the technical depth of most who visit here I'm sure I can follow. 

I've had 22 Hornets and K- Hornets loving the later most. I had one custom 218 Bee that I loved also and they both ran around 30-34K pressure. Now I have a 44 in 38-55 and you guys have warned me about pressure and longevity so I load soft for it with 4198, Unique and 4759 guessing 20-25k psi an educated guess. I also load 2ff BP at lower pressure when I have the yearning. Can't help myself with BP I think it's like an aphrodisiac. But I'm seriously contemplating a small 25 cal on a Stevens 44. 

In your experience what level of pressure is likely to batter a 44's pins. What pressure gave you performance and accuracy without worrying about excess wear ? And lastly as I noted I have a old nice 44 in 38-55 but also a CPA in 38-55 so should I or could I load the same for both guns and expect similar results to 200 yards ?

I was thinking about a 44 with a shot out/corroded barrel but what do you think about just having CPA make me a swap barrel for my 44 1/2. Haven't run the cost numbers just spitballing now. Then again what about the 25 Hornet ? Though I'd like to stay away from anymore wildcats. 

As always I appreciate the combined wisdom offered on this forum

Rick

Thanks that reassuring info but I have my perfect squirrel rifle a T/C Cherokee 32 cal muzzle loader with double set and great balance. My first Cherokee burned up when T/C's big shop went up in flames years ago. It was in for new wood, a back door job from a friend and neighbor who worked there so the rifle did not exist on the books so not covered. Found another three years ago so my Fox, gray and black squirrel population knows it

Rick

Ain't that a bitch casehead seperation. My first Hornet was a beat up Winchester 43 that had a headspace problem, I learned later. As you know the brass is notoriously thin and weak and I ruined about 10-12 cases all from bad headspacing.  I was young and stupid and just figured I was loading too much WW 680, too hot. My cases all looked like yours. Then I got a T/C 83' and had T/C make a K Hornet out of it. Never had brass problems again. Love the K Hornet. 

Rick

No, please no math for me. I should have mentioned that my chamber is oversize. IF it were smaller the thin Hornet brass would stand up much better. My kiss fix is to rechamber to 25-20 Winchester because I have brass and a chamber reamer. Keep it simple stupid for me. Math just confuses me.