Have you seen a gun improve from a 2 MOA to 1 MOA or 1.5 MOA to .5 MOA with solely a different ammo or is it more incremental improvement?
Yes. Getting ready for an elk hunt in 4 weeks, just tried 5 different loads for a Tikka T3X in 270Win. These were 5 shot groups at 100 yards. Shot 150 ABLR’s into .5 MOA. 150 Bergers with two different powders into 1.25 and 1 MOA. 145 ELD-X with two different powders into 1.5 and 1.3 MOA. This same rifle will shoot factory Barnes Vor-tx ammo with 130 TTSX’s to almost .5 MOA and 129 LRX’s into 1.2 MOA for 5 shots.
The 150 ABLR‘s are going on the hunt. Will do some 10 shot groups with the 150 ABLR’s and expect the rifle to stay at or just under 1 MOA. If I really take my time and have a good day, maybe get close to .7 or .8. As long as I can shoot it to about 1.5 MOA at 500 off the bi-pod I’ll be very happy.
All of the following are two 5 shot groups for a 10 shot aggregate, or three 3 shot groups aggregated, or some combo of shots very similar. All at 100 yards unless noted differently.
Two other 270 Win Tikka T3’s perform similarly to the T3X 270 mentioned above with a variety of factory loads, in terms of pretty good shooters. Almost all loads under 1.5 MOA. But their most favored loads end up about 1 MOA. Neither one has ever come close to a .5 MOA group. Neither one has been much over 2 MOA. Good solid consistent hunting rifles accuracy wise.
I have a Rem 700 in 280 Rem with a #5 Brux barrel that shoots nearly everything into .75 - 1.25 MOA. It likes 145 LRX’s the most and gets to .65 MOA with them at 100 regularly. Pretty good and consistent shooter. Was able to hold it to 1.33 MOA at 600 yards with the 145 LRX’s for 8 shots. This gun has not shot anything terribly.
Have a couple unaltered Rem 700’s, 25-06 and 280, that are not nearly as consistent. Favored factory loads 1.25 MOA range, stuff they do not like up to 3 MOA. Then had 2 two older Rem 700’s with their skinny taper Rem barrel, early 90’s stuff iirc, they gave me fits. Tried 8 - 10 different loads, 3-4 MOA, messed with bedding, and finally found one load that shot OK in one of those rifles. The other got the Brux barrel referenced above.
I have a Rem model 7 with the skinny 20” SS factory barrel in 7-08. Surprisingly, to me anyway, may be the most consistent rifle I have. I have put quite a few different flavors of factory ammo through it. Nothing much better than 1.25 MOA or worse than 1.5 MOA. It had its trigger worked, everything else is stock.
While every rifle is different, I tend to agree with the posters above that good barrels shoot most stuff well. My experience with custom barrels is not expansive, just a couple Krieger and Brux barrels. The Tikka’s perform very close to the custom barrels. Lower end factory barrels can be much more erratic. Been my experience anyway.
Anymore, I’ll get 3 different factory types of ammo with bullets I can live with. If my rifle has proven to shoot well already, I nearly always have one or two that make the grade. If it’s hand loaded there are usually 5 options. I no longer mess with finicky rifles. They get put in a corner and later get a new tube or moved on as a donor action.