Did somebody actually ask if a 4" 45-70 would have any muzzle flash? Probably at least 10'-15' of it.
Most of the shorties I've seen have been 4"-6" Contenders chambered for standard "handgun" cartridges.
As a huge fan for decades of the biggest, meanest, baddest I could shoot safely on my Contenders, the 10" 416 Rigby barrel I had for my Encores was short enough for that cartridge. While even full house loads didn't tear me up to shoot to bad, the muzzle blast was almost unbearable.