Quote History Originally Posted By newBMowner:
Every rifle is different
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This is the thing with factory ammo - you really don't know until you test it in your rifle.
Plenty of factory ammo is "consistent" enough to be accurate, but the question is whether or not it hits an accuracy "node" in your gun. Small dimensional differences in bores and chambers (and thus pressure/velocity) affect this, which is why it's not guaranteed that otherwise identical models will shoot the same ammo well.
Also, you will want to test in "final" configuration (with whatever brake or suppressor you are going to use), since that affects the harmonics.
As an example, I tried several factory loads in an RPR in 6.5 Creedmoor, and it turned out that 120gr Amax and then 143gr ELD-X both shot the best. Until I put the suppressor on, and suddenly the Prime 130gr took the top spot. Without the suppressor, the Prime shoots around 1 MOA. With the can, less than 0.5 MOA. It's not the fault of the ammo.
My R700 with a high-end barrel shoots the same Prime 130gr at just under 1 MOA no matter what's hanging off the end, but the Hornady is better. Again, not the fault of the ammo (but I want to play with length now....).