Q: What are masterwork rolls?
A: Most legendary weapons are capable of being Masterworked. The masterwork system is a way for you to upgrade your favorite weapons to their maximum potential.
Q: What does it take to upgrade a weapon to a masterwork?
A: Upgrading your weapons, in broad terms, takes a small amount of glimmer, legendary shards, and, most importantly, Enhancement Cores.
Depending on what Tier your weapon is at, the requirements to raise it to the next tier increase the closer the weapon is to being fully masterworked (Tier 10).
Q: What benefits do I get for masterworking a weapon?
A: Each tier that you increase your weapon will grant a small buff to a single stat, chosen randomly when the item drops.
Beyond that, at Tier 5 you gain access to a kill tracker. At Tier 10, your multi-kills will generate orbs of light.
Q: So what are these "masterwork roll" stats?
A: These are the possible stats that upgrading your weapon will grant a bonus to. Depending on what tier you are at, you can grant anywhere from 1-10 additional points in any of the stats listed to your weapon.
Q: Any catch with this?
A: The Bungie API currently says that all weapons can potentially roll with all stats as their masterwork stat. This obviously isn't accurate, as Blast Radius isn't applicable to, say, Auto Rifles.
The list you see on this page is trimmed to only show stats that actually appear on the weapon. However, it is possible that Bungie has additional logic behind the scenes that further filters these
possibilities to, for example, prevent certain items from being able to have an Impact masterwork. Until Bungie modifies the API files to 100% accurately display which masterwork stats are possible on
each item, take what you see here with a pinch of salt.
It does literally nothing extra to the weapon. No extra stat, no increase in the ammo it replenishes, nothing.
If you want this on a special weapon, just use the unenhanced version and save the Ascendant Alloy
Other than that, it can keep your mag going for noticably longer, though currently, weapons that can support this perk have better options (at least given the rolls they're capable of. I know subsistence can be really good with some combos, just not these ones currently available imo). And again, I would still hold off on using the enhanced version, especially when you have your other perk to worry about first.
For very small magazine weapons the higher % refresh might not mean an additional round is refreshed by the time the game has rounded each value up to the nearest whole number like it does. For example, I have it on a RAGNHILD-D with a 6 round mag now and it refreshes 2 per kill. However, if I drop it to a 5 round mag then there is only 1 round refreshed per kill. This is likely the result of the enhanced perk for a special weapon being 20% refresh, which is 1 for a 5 round mag for 1 round refreshed and 1.2 for a 6 round mag for 2 rounds refreshed. Meanwhile the standard perk's 10% refresh will always mean 1 round for a shotgun.
I have not tested with any other special, but I imagine the values are equal across specials making the 6 round breakpoint the key for any shot/sniper/fusion that might have the option for enhanced subsistence.