I personally believe it's a good idea to know if your accuracy issues are "the gun's fault or your fault".
There's two ways to find out: either have a known good shooter run your gun and see what happens, or you "bench test" it yourself: fire it from a two-handed hold, barrel resting on a sandbag (best case) or rolled-up old towel or blanket or whatever. (Note that it will likely get some burns from the cylinder gap so make it something you don't care about - not your best jacket
.)
Doing it yourslef can actually be better with an SA as it takes a bit to adapt to those and your "test shooter" may not be very good with one.
If you try it yourself, it's important to shoot at the same target every time, rather than "chase your holes all over the paper". Even if your groups are landing high and/or off to the right or left, the first thing you care about is group size. That tells you if the gun is fundamentally any good. Remember to try this with two or three quality rounds. If the gun is a 357, I would recommend trying at least three of the following for accuracy: Speer's 135gr mild 357Magnum Gold Dot "short barrel", Speer's 158gr 357 Gold Dot, Hornady's 158gr XTP 357, Cor-Bon's 125gr DPX Barnes-based all-copper 357 hollowpoint, Federal's 140gr 357 Barnes-based all-copper hollowpoint, and at least one quality 357 hardcast solid of 158gr or better yet, 170 or 180gr.
In my gun, the Speer 135gr 357 remains the best factory ammo I've shot, doing 2" off the bench at 25 yards. This is a good low-recoil defense round. In contrast, Speer Gold Dot 125gr high-speed JHPs as loaded by Doubletap group at least 4" to 5" no matter what I do, with over double the raw energy.
Barnes-based all-copper slugs have a good rep for accuracy among the lighter slugs. Since copper is bulkier than lead for the same weight, the slug is physically long for it's weight which gives you more surface area hitting the barrel's insides as compared to the same weight lead-core jacketed hollowpoint. Speer and Hornady jacketed lead-core slugs both have good reps for well-balanced (hence accurate) slugs.
Once you know what the gun is capable of, it's my experience that it helps you know to what level you need to progress. This process also tells you whether or not the gun needs tweaking to get the sights dialed in
.