I did some testing with the new ways you can customize your bowguns MHW:
First ignore the noobguide that shows on customization screen and press L3 to bring up the ammo list, since it gives more precise info.
Special ammo is not affected by any mods.
Shield is only for Heavy Bowguns.
+1 Small nudge, can keep moving and shooting.
+2 Stronger nudge, can keep moving and shooting.
+3 Small backhop, stops movement.
+4 Large backhop, stops movement.
Fast, quick bolt pull, can keep moving.
Normal, slower bolt pull, can keep moving.
Slow, braces gun against ground, stops movement.
Very Slow, rests gun on knee, stops movement.
10% damage boost each mod, stacks up to 30% with 3.
From point blank to a bit under 1 roll range away from the target.
The range is just 1 step shorter than the max optimal distance of spread shot.
No effect on special or status ammo, (Slicing, Sticky, Cluster, Poison, Paralysis, etc.)
10% damage boost each mod, stacks up to 30% with 3.
Starts at a bit over 2 rolls away from the target.
The min range is one step further away than max optimal range of normal shots.
No effect on special or status ammo, (Slicing, Sticky, Cluster, Poison, Paralysis, etc.)
(Note, I did not test these personally due to time it would take)
1: Same as Sword n' shield.
2: Same as Greatsword and Chargeblade .
3: Same as Lance and Gunlance.
TL:DR.
Aim for these:
Recoil:
+1 or +2 recoil on your preferred shot(s).
Reload:
Fast or Normal reload for your preferred shot(s).
Long Range:
Only if you mainly use pierce and elemental shots. (All other shots have either too short critical distance or not affected by the mod).
Close Range:
Only if you mainly use Spread. (Technically Normal shots as well, but they have a bit over double the crit distance compared to the mod effect distance).
Shield:
If you want to play extra safe or are running a glass cannon build.