How is short barrel ammo different? Gold Dot

Looking at Speer Gold-Dot 124.Gr JHP 9mm.
Regular is advertised at 1220fps part#888-798 and short barrel is advertised at 1150fps part#216-634.

How do these loads differ?
What length is “short barrel”?

I couldn’t find much on Speer’s site, nor the search engine here.

Thanks

1

The short barrel loads are designed to work at lower velocities…< 4". They are designed to perform on par without standard loads but lower velocities.

I’ve heard some of the Short barrel bullet makers claim the construction of the bullet is so that it’ll expand at lower velocities.

You can tweak the size of the hollow-point, the hardness of the core, the thickness of the jacket, and the number and length of the cuts in the jacket.