28” or 30” ballistically different.

Is there any difference in the pattern of a 28” and 30” barrel with same choke and cartridge? I appreciate the handling may be different

Testing that on a pattern plate would tell you, but unfortunately I don't have two of the same guns with the only difference being barrel length. So with the caveat of not having fielded a trial, I would say I strongly doubt there would be a discernible difference. My reasoning would be that a pattern forms after the wad pushes the shot out of the barrel, and the only difference between a 28 and a 30" barrel might be a different velocity. 

If the powder-into-gas process is still increasing the pressure in the barrel at the point where the wad / cup passes 28" (and keeps doing so), the muzzle-velocity of shot leaving a 30" barrel would be higher as it has more barrel length where the velocity (still) increases. If maximum gas volume has been reached at say 26", it could be that the MV of the 30" is lower than the 28", given the extra friction the wad and shot have to overcome in the remaining length of barrel to traverse.  

Then there is the rapid decline in velocity from the muzzle exit onwards, which rapidly negate any velocity difference (if there is one). Then it takes a further split second for the shot to part from the wad or cup, and then there is the pattern being formed by the shot. If there is any velocity difference at that point, that could theoretically effect dispersion and pattern... In real life, I doubt that 2" of barrel length would yield a very different spread, but I could be wrong.  

If anybody cares to pattern plate with the only variable being barrel length, I'm all ears. 

Differences so minuscule and random as to be unpredictable and undetectable. 

It's a shotgun - get over it

:hunter:  

No - The old textbooks all say the barrel has done its job after 24 inches. The rest is balance.

I think some cartridge speed tests have suggested very minor differences with modern plastic cartridges and back bored barrels and the right chokes - at which point you wouldn't bother with 28 inches anyway.