I haven't tried it but from what I read in the patch notes, it seemed like Quality of Life changes.

This was their logic:

If gunbreaker did not manage their cartridges carefully during burst phases, executing Bloodfest would result in cartridge overflow. To rectify this irritation, we have added an effect to Bloodfest that increases the maximum number of cartridges available.

When battle mechanics required gunbreaker to distance themselves from the target, the recast timer of Gnashing Fang would often become a hinderance during burst phases. We changed Gnashing Fang to a charged action to help alleviate this issue, but also had concerns that executing an optimal rotation while under the effect of No Mercy might overcomplicate the management of recast times and cartridges. In order to maintain a proper balance, we have shortened the recast time of Bloodfest and adjusted the cartridge cost of Double Down.