JP Custom Silent Captured Buffer Springs

[Drifter]

For what it's worth, rifle-length buffer tubes usually have a smooth interior finish, where as carbine tubes often have a rougher mil-spec type inner surface. Consequently, rifle tubes tend to be quieter in my experience, especially when combined with a flat wire buffer spring and a touch of grease. This might vary by brand, but it's what I've noticed in some builds.

Think I read somewhere that JP designed the captured spring because it was difficult to get polished buffer tubes that met their preferences. Thus, the finish inside the tube seems to be a factor in how much spring noise is heard / felt by the shooter.