Say you are trying to hit a 10 inch target...

For comparison, let's use a .308 Win shooting a BC of .51 at 2650 fps.

How much more range does a .300 RUM have shooting the same bullet but at 3250 fps?

How about a .338 300 SMK at 2850 fps? How much more range than the .308?

Do you mean in terms of PBR or hit probability if no correction is made for wind or something else?

For me it would boil down the range at which slight errors, say by a 2-3 mph, in windage would not push the bullet by more than the radius of the kill zone.

I can crunch some figures but but you can see the basic approach.

I am talking about wind. Assume rifle accuracy is not an issue, nor is knowing the range.

Ok thanks, given what wind?

If it's a steady 5mph from 3 o'clock or a fishtailing wind gusting between 15 and 30mph, from between 7 and 5 o'clock?

In general the Utramag would have about have just under a minute less windage in a straight 15mph crosswind than the .308 with the same bullet.

The kill zone of the 10" has a radius of 5", so in my estimation you have an error of +-5" in your wind solution estimate.

At 100 yards this gives a range of windage You would have to mistake a 75mph crosswind for still conditions to miss with the 308 and about 100mph for the RUM!

Moving to 300 yards a cross wind estimation error of about 8mph higher or lower than actual would push you out of a kill zone with the 308, an error of of 11mph in estimation with the RUM.

At 500 yards a crosswind estimation error of 2.5mph for the 308 and 3.5 for the RUM would push you out.

On that basis I would concluded that there isn't much in it, up to 300 yards you'd be hard pressed to tell the difference assuming a half-way competent shooter and by the time you get to 500 yards and beyond you are tending towards the point of diminishing returns.

IMO the only point of the big case calibres is to launch heavy high BC bullets at higher speeds tah possible with small cases.

Try a .208gr Amax in the RUM at 3150-3200 in the software and it completely outclasses the 308, something like 100 yards more windage error tolerance out to 600.

The 338 SMK with it's BC of seven and half of course best the above, but only really past 1000 yards.

I can see that needing the extra retained energy might be an idea but I'd rather hunt with an Amax than a SMK.




Leaving aside the fact that I would be shooting the 208gr Amax in a long range hunting role in the RUM, if my wind reading confidence level was +-5 mph, I would be say that on the basis of forgiveness of windage reading errors alone, the RUM has

Can't give you an exact numerical answer to your question, but can say that at some ranges where the targets go beyond the 1000yd mark, the 308 is not permitted to be used due to excessive drop. Remember there are people in the target pits and "lobbing" rounds at say 12-1500yds there is a distinct chance for the round dropping in on the pit crew. Minimum round is usually the 300WinMag if that helps answer the question. Off topic a bit regarding flight of the bullet, but I was always told to consider the impact the wind has on the flight for the first 1/3rd of the range. Theory is that upon leaving the barrel the bullet is immediately impacted by whatever wind speed, direction and not much you can do about the wind beyond the first third of the flight. Obviously if you can determine that the wind is really gusting heavy way down range either adjust for it or hold up, but again, pretty much out of your control. Some skilled shooters will attempt to monitor the wind at half way down range and if you can do that, fine. Wind speed itself is not that difficult to determine, but actual direction is more difficult.
Big difference on adjustments if something other than full value wind, 3 or 9 o'clock. Military has done endless research on reading the wind and proper adjustments and there are simple formulae that can help quite a bit.

The wind speed doesn't matter. What I find interesting is that most shooters would think the .308 load doesn't come close to the RUM. The slower .308 drifts 2.5 inches in a one mile per hour wind at 560 yards. The RUM drifts that much at 640 yards. The difference is only 80 yards. Granted, 80 yards is 80 yards, but it isn't like the RUM gives you hundreds of more yards.

The .338 300 SMK at 2850 has the same drift at 730 yards, 90 yards farther than the RUM.

I used 2.5 inches as a comparison because no rifle shoots one hole groups at reasonable range. Assuming you can keep your groups at 1/2 MOA in the field, the differences are even less, because as the size of the group increases with increasing range, the amount of target "freeboard" drops as well. Of course, as range increases, the amount of drift increases tremendously. But that also gets into one's wind estimation error.

"The wind speed does not matter??" Not sure what you mean when you say the speed of the wind does not matter??

Wind speed doesn't matter; your ability to estimate it is. In other words, the .308 in my example drifts exactly as much at 560 yards as the RUM does at 640. But the real difference is even less...

Let's say you estimate the wind within 1.44 mph. In the above examples, if i can shoot 1/2 MOA at 560 yards, I can shoot 2.8 inch groups; that leaves me with 3.6 inches ((10-2.8)/2) of kill area I can "drift" out of, or an allowable error of 1.44 mph - exactly our error.

Theoretically, the RUM has the same drift at 640 yards. But if our group size is 1/2 MOA, it is 3.2 inches at that range, leaving us with 3.4 inches of kill area for wind error. The problem is, we need to be able to estimate the wind within 1.36 mph now or we will miss.

Using the .338 example, our group at 730 yards is 3.65 inches, leaving us with a kill area "surplus" of 3.175 inches. But, since our drift is 2.5 inches per one mile per hour of wind, we must estimate the wind within 1.27 mph.

My point is, as the range gets longer, you are not only fighting increased drift, but larger and larger group sizes.

Guys who claim to shoot game at 1000 yards would have to estimate the effects of wind within 1/2 mile per hour or they risk missing. Since the TOF is 1.3 seconds, you not only have to estimate it within 1/2 mph, you have ensure it doesn't change in that 1.3 seconds as well.

But then again, I don't think these guys are claiming to make one shot kills 90 percent of the time. Statistically, if you can only hit the first time with an 80 percent probability, your odds of missing twice in a row are less than 1 in 20.

I think you're selling both the 308 and 300 RUM way short. I can shoot 155 grain bullets with a .5 BC well over 3000 fps in my 308 with a 30" barrel, and my buddy gets just about 3000 with his 24" barrel.

The advantage in wind doesn't "really" matter, as long as you can read that wind. If you can't, then the 300 RUM is most likely going to be off a small target as well.

Tyler:

My point is, the advantage of the bigger cartridges is not in the hundreds of yards, assuming the limiting factor is your ability to judge the wind.

I would argue no one can estimate the effects of wind within 1 mph 90 percent of the time. That becomes the limiting factor.

Wind constantly fluctuates too in speed and direction between you and the target.

BC is the name of the game, not velocity

I would just use the maximum range that the bullet would stay supersonic. If the wind estimate is constant (gravity already is) the drop and drift should be constant enough to call your shot. Once the bullet goes transsonic all bets are off.