which component is most critical for making great bullseye ammunition, reloading

If one removed the human variables of grip and stance and trigger control and quality of firearm, wind etc....imagine for example a computer that shoots a meticulously brilliantly and as near perfect a firearm as possible....all fixed and stabilized in a fixed armature.

I appreciate that this is a multivariable scenario where choice of powder and type of primer might work together or against each other....or the weight of bullet, shape and length of bullet are integrally related to barrel rifling and distance shot etc

 ..... but for the sake of education....let's consider the contributory effect of a "single" characteristic or element.

Is the projectile the most critical single component
or powder choice
or case length
or crimp
or primer type
or primer set depth
or concentricity
or neck tension
or chamfer
etc.

thank you

#1 by a mile is bullet choice

Generally speaking, rifle shooters feel that 90(+) of accuracy is attributed to the bullets.  No matter how much you alter the load, bad bullets will never shoot well.   Then comes powder type and charge, but in pistol there is way more leeway in powder selection.  Then is assembly mechanics, then ignition.  

But before you start diving into a rabbit hole, remember bullseye pistol doesn’t require exotic reloading techniques.  A good gun will shoot about 1.5 inches at 50 yards.  That’s 3 MOA.  If your reloads shoot 2 inches or 2.5 inches ar 50, that’s certainly good enough to shoot good scores.  For me at my level, if the gun and load shoots into the X-Ring at 25 yards, that’s good enough for training.  For matches I might search for better like 10 shots INSIDE the X-ring, but I still,have to shoot it.

thank you, this information is very helpful as i now have a better handle on how to apportion my funds and efforts

B-n,

Have you reviewed the recommended loads in the "stickies"?  That will save you a bunch of time, because you will likely find you will be limited by availability of component choices - that is the bad news.  The good news is that there are dozens of load/bullet/powder combinations that are "good enough".  The criterion above, "all inside the X-ring at 25 yds" is not that hard to meet.  That's 1.68"- 0.45", or about 1.25" C-C at 25 yds, or 2.5" at 50 yds - dozens of load combos easily meet that criterion in a gun that can shoot.  So I suggest you try some combos as presented.  You can experiment if you like, but don't waste a lot of time with it.  Sevens and eights at 25yd are very rarely due to the load used.  As many have said here,  "its the archer, not the arrow", "they don't award Distinguished Reloading Badges", etc., etc.

Good shooting.

Edited to add:  Heck, just use anything fc60 shows, see his recent post  - he's got the groups to prove it!

makes so much sense, thank you
i am so enjoying the journey, learning and striving for improvement..... tempered of course by my own limitations and practical realities