devtrackers.gg
2 piece bonus: 30% reload speed (i just think that reload speed is not that great of stat so i slighty made it bigger)
3 piece bonus: 20-25% magazine size increase (most automatic ARs and SMGS get around 50 rounds extended, so with this they would just be around 60 like EB and would be a better DPS increase making you kill enemies a bit easier without special ammo and WITH special ammo)
4 piece bonus: keep how it is. Justchange that if you kill an enemy with hollow point and they die it also count for the set (fun trivia if the enemy has 1% health and you shoot him with hollow points, you don't get them back, but if you are playing a surivalist it WILL count as status effect afflicted for your crossbow ammo AND same happens if you kill enemy with an seeker mine it will give you ammo even if the explosion is what killed him before causing bleed)
Chestpiece: keep how it is
Backpack: Either make it so you get extra ammo every kills (let's say you would now get 1 magazine and a half), another possible suggestion would be that your other two weapons also get 50% of their magazine as hollow point ( so you lose all your ammo in the main gun, both of your backpups can also be used to get more ammo back but less reliably), and possibly final suggestion similar to original post if you are empty when you reload you get up 30% of your magazine as hollow point ammo (so let's use an AR again as example you would get 18 shoots to kill an enemy, enough to start and do some small extra damage, not enough to make an entire magazine look worthless).
This is focused on bringing more weapon variety because hollow point mechanics limits weapon choice making it currently mostly a LMG only set. This should alleviate by giving players indirect DPS boost with magazine sizes and small buffs to total ammo when using the backpack so you can stay with the bonus more often to counter the many issues the set has with high difficulty and group play at the same time