TargetTalk

Success depends - 90% on shooter 10% on rifle/ammo combo.

Your opinion and why...

It's the Indian not the arrow...but, if you have a really good pistol/ammo combo that helps...

...and the athlete is responsible for getting a good rifle or pistol/ammo combo, so 90% + 10% = 100%

A more helpful answer is that live fire is a way to get feedback on your performance and process. Good ammo provides more "truthful" feedback which should help you learn and progress more quickly. Bad ammo "lies" to you (sometimes), making it much harder to make good decisions.
Life is too short to shoot bad ammo. Instead, mix in dry fire shots to mitigate the possible cost difference per trigger pull. Call your shots, work with a coach, go to a clinic or camp, use a SCATT, etc.
Live ammo makes sense when working on recoil, shot calling, competition practice, etc. Training your hold, breathing, sight picture, shot process may require little or no live fire. After working on that type of topic for a while shoot some live shots with good ammo to see feedback on results.

Depends on the match, 1200yd rifle the rifle/ammo/scope is quite important, IPSC you could win with a smoothbore shooting balls as long as its reliable, but ultimately the athlete is responsible for getting everything together - thats the whole point.

I always tell people that serious target shooters spend big money on equipment that makes it a little easier to shoot. Things like anatomical grips, large bladed sights adjustable triggers - none of those make the gun more accurate in their own right; they make it easier to get a good shot off.

That said, a good shooter will always do much better with a bone stock consumer firearm than will a crappy shooter with an Olympic quality target pistol.

As far as percentages, I have no idea.

90% on the shooter. There are only s many rifle/ammo combos, but human capability to foul up is unlimited (ask any coach).