As per the 2.75" length, yer messin' with the lower limits of operating pressures...probably. Factories can have some "tools" available to them that we don't.
That being said, as much as a little extra length is not likley to spike pressures to a dangerous level in a low pressure load, you might run the risk of leaving the wad in the barrel if you put the 2.5" shell in a 2.75 + incher...especially with long cones or "over" bores.
Plenty of tricks available to get this to work safely in longer chambers as well I imagine...never know 'till ya cut one open and poke around a bit.
Best,
Mark
