In a 7mm-08 with a 24" barrel shooting a Barnes 145 LRX.

Probably not just a whole lot.

It depends on several variables, but about 50 fps.

When I go up in .3 grain increments during load testing, I will gain about 15 to 20 fps each .3 grains under normal circumstances (depending on the case size, and bullet weight). So, a full grain should be about 50-60 fps. But if you reach a max pressure load or are already above max, adding more powder will decrease your fps. This is why a chrono is just as important as seeing the target group sizes. I know I reach the rifles' max charge when the velocity levels out (no fps increase) when you go up in powder. If you keep adding more powder, fps will actually go down.

In my experience, about 60 fps

IMO neck tension and run-out play a much bigger part in consistency. Keep in mind that the ammo made for the Palma Tophy Match championship was all drop charged on a Dillon 550 a few years ago. David Tubb himself doesn't start weighing every charge for match ammo until he's past the 600 yard line according to his videos.

I think it matters, but likely not as much as most think. I have a RCBS Chargemaster 1500 so I measure every charge just because it's convenience, but depending on the powder you're using, you could better served by getting a good powder measure, and spending more on some bushing dies/comp seater.

That said, to answer your specific question I believe it depends on the powder you're using. 1 grain of Win231 is very different than 1 grain of IMR 7828. Assuming you're not on the fast end of the 7-08 powder spectrum, it's probably not much at all (25-50 fps)

So when we are talking about one grain I understand that it can mean a difference of 40-60 FPS but what does that mean at 100, 200, 500 and 1,000 yards relative to POI.

Not much at most distances; again this depends on the powder and the cartridge. Any over charge means more at 1k than at 100. That said if I had to give you a number 40-60fps, means .1 at 100 and roughly 2" at 1000;again, if I had to guess. I sincerely think run-out and brass prep mean much more than any powder charging regardless of distance.

Although powder charging will impact this, the biggest factor you need to look at is vertical stringing; horizontal is likely the shooter, vertical is likely the reloading process.

Without question the powder charge should remain as consistent as possible, but so should annealing, neck tension, neck thickness, brass cleanliness, and primer depth. Consistency is critical to groups at long range; quite literally how you pull handle on the press matters if you're looking for extreme accuracy at long range.

It's all a matter of how detail oriented you want to get, but you reach a point of diminishing returns after a while IMO.

If you gain in speed, then the bullet will drop slightly less and hit higher. Typically (but not always), as you increase powder charge, your POI will hit higher, even at 100 yards. For example, when I am dialing in a rifle and shooting for groups at 200 or 300 yards (especially at 300), the groups will start impacting higher and higher. I'll dial the impact down .1 or .2 mils (or .25 to .5 moa) between groups to center up the group on the target more. That's normal. But this is over about 2 grains of powder from first groups to last groups. The 1 grain of powder gain in a 7mm-08 case with the 145 grain bullet, it should have about a 50-60 fps difference. If you are zero'd at 100 yards, you may or may not see a noticeable difference in POI. If there is, it will be very slight. But at longer ranges, like 500 and out, you will see the higher charge weight hitting higher, simply because it's going faster. The know exactly how much higher, you need to run the trajectory calculations.

Assumptions:

• 1 grain = 50 fps difference
• Bullet: .284 145 gr Barnes LRX
• Sight Height = 1.5"
• Zero at 100 yards
• 2750 fps vs. 2800 fps

Conclusion: 16" difference in drop at 1,000 yards

Exactly! From about 500 and out is when you start to see a noticeable difference. Closer in, not so much. But that also doesn't take into consideration what that 1 grain difference does to the accuracy of the round.