I have a question for the all shooting experts in here. In a black powder rife is there a huge difference in accuracy between a 26" and a 28" barrell if you are shooting between 100 and 125 yards?

No, maybe twice that range it would matter more.

Maybe a slight, and I do mean slight difference in projectile velocity. Nothing you will notice or the animal your shooting. I'd shoot that distance with a 21 inch carbine if I had to.

As Cayugad said, the difference would be in velocity but not much. Same goes for accuracy. But all other things being equal you should not see a noticable difference. Even the 2" sighting plane difference is insignificant.

Actually if you think about it a shorter barrel would be stiffer and in theory would be more acurate. Many more varibles than barrel length that go into making a accurate gun. Now for off hand shooting a longer barrel may have an advantage but it is from the increased sight placement and heavier weight making it easier to hold steady. Barrel length and accuracy is just one of those old wives tails, increased accuracy was associated with the longer barrels because they are steadier to hold when shooting off hand, but the oldtimers didn't understand so thats why the long barrle mith came about.

It depends on the barrel. A Knight 26" is actually 25 1/2" from bolt face to the muzzle. T/C Omega 28" is actually 26 1/2" from bolt face to muzzle. The last 3/4" or so doesn't have rifling so it doesn't contribute to thevelocity soyou won't see much difference. An actual 28" barrel vs an actual 26" barrel and youshould see more difference withthe heavier powder charges.

How about "porting" on the barrel, does it help that much with black powder shooting?

No there is very little differance in velocity and none in accuracy.
No, I tried porting a barrel, very little differance in recoil [which is why it is usually done] it makes a lot more differance in high power smokeless guns because of the gas under several times more pressure when it escapes the port has a rocket push effect to reduce recoil. The real differance in having ports in a BP gun is that you have to clean them now thats a pain where th sun dont shine. Lee

In CF's I believe it is 100 fps loss for every inch of barrel loss (approx). As for ML's it would have to depend on your charge and what the barrel is capable of burning within that length. I would think that if you were to bump the charge a bit in the shorter barrel you could equal a lesser charge in a longer barrel.
Does any of that make sense???

edit: I never did reply to the question. ...Yes with the same load there will be a "difference" Bump the shorter barrel by 5-10 grains and it aught to equal out.

For my typical hunting loads (80 - 100 gr) I can see no advantage to a barrel over 26", and even a few inches less isn't a real disadvantage. If you are using 150 gr charges there would probably be a velocity gain, but in most cases an accuracy loss. The velocity gain is usually minimal, and the accuracy loss can be dramatic. I've owned onlya couple rifles that would shootreally heavy charges (130 - 150 gr) with anything close to acceptable accuracy, and dropping back to 110 - 120 gr really improved groups with not too much of a drop in velocity.