I've been looking at some numbers between the 300 RUM and 300 Win Mag in the Nosler manual. I have a 300 RUM that I'm loading with 180 gr Noslers and 4350 powder. According to Nosler, this is the most accurate powder for this bullet. Max is 82.0 gr at 3187 fps. The same powder and bullet in the 300 Win Mag comes in at 3130 fps using 70.0 gr. That's a 12 gr difference and only 57 fps between the two. How can this be? Is this simply because the 300 RUM has allot of volume not being used? Max on the 300 RUM is at 86% capacity. On the 300 Win Mag, it's at 91% capacity. Even the other powders used don't offer much difference between the 2 rifles. I'm just contemplating if my 300 RUM is really worth the extra case capacity. Seems like the 300 Win Mag can come very close to doing the same job with less powder.

I can assure you that you are not getting anywhere near the full potential out of your RUM if you are loading 4350 of any variety. What Nosler says about their most accurate load doesn't interest me, what load is giving me the most accuracy coupled with highest velocity does. Try some R25, 7828 or H1000 in that gun, you might be surprised at what your chronograph says.

As pointed out above you need a slower powder to take advantage of a larger case in the same bore.

The smaller case usually does quite well against the larger one with medium weight bullets. Some say that even a velocity of 3100 fps is kind of high for good bullet action. Better to load 200 or 220 gr bullets in that RUM. Then I will leave the smaller case behind with the right powder.

That's too fast a powder for the application. H1000, RL 25, Retumbo, etc is the speed range you want to use.

There are quite a few people here getting over 3400 fps with 180's.

So, no, they aren't the same.

Many people that don't fully understand reloading or ballistics are easily confused by the loading manuals.Because of the great difference in case capacity each of these cartridges performs best with powders of very different burn rates.I am able to get 3375fps out of my 300ultramag using r-25 which is an optimum powder for the ultramag as larger cases do better with slower powders.The 300win mag onthe other hand produces better velocity with faster burning powders such as imr4350.If you were to use r-25 in the 300win mag you would not get optimum velocity because you would not be able to fit enough inside the case.If you are going to compare two cartridges you must do so with both loaded with optimum powders.The loading manuals confuse things by even listing loads for the 300ultra mag with such an unsuitable powder.Then again you shouldn't judge a cartridge based on a single loading manual as the particular barrel they are using as a test barrel may be a particularly slow barrel or they may download it greatly because they don't have a proper pressure barrel for that particular cartridge.People have to realize that loading manuals are only guides and that the velocities printed may be very different than what their own guns will produce.

jethro - as stated above, try IMR7828 with a 200 grain Partition for a very noticeable increase in usable velocity / accuracy - tinker with the cartridge overall length to obtain best grouping - the 300 rum rocks !!!! KMule

For the RUM:
AA-8700 From 100.8 grains to 113.0 grains
Remington 9-1/2 Primer

For the 300 Win:
IMR-4831 From 59.4 grains to 75.5 grains
Winchester WLR Primer

Believe me, I'm not knocking the 300 RUM. I absolutely love mine. I also realize I'm not loading the optimal powder, but I would rather shoot the 10 lbs of the stuff I have than throw it away. It's getting pretty old and I want to use it up. Anyway, all I'm asking is how 12 gr more of 4350 can only produce 57 fps more in the RUM. I know all guns aren't the same and all manuals aren't the same, but I'm sure Nosler didn't just pull these numbers out of a hat. Maybe it's my engineering background, but I'm looking for a technical explanation. Just saying that the 300 RUM likes slower burning powders doesn't get it. Tell me why by comparing apples to apples (same powder and bullet in each). I know the basics. Now let's get in the weeds. Just trying to strike up some interesting conversation.

Jethro, I don't know the exact formula, but it basically is powder burning rate/case volume=expansion gases (which X barrel length/volume = velocity). I'm not trying to put a math face on this (because I can't) but that seems to me to encompass all the variables (except temperature) involved. You might also think of it as differant grades of gasoline for a car engine. Yes, you can probably make your 11 to 1 compression high performance engine run on 87 octane fuel, but not nearly as well or as powerfully. You'll just burn more gas. In the case of your RUM, with 4350 you reach the point of diminishing returns more quickly then with slower powder, which is what you see in your numbers. There is even a loading method that uses the speed differance between each shot/load as a way of determining whether that is an "efficient" (for want of a better word) load for that particular cartridge, and tells you that when the speed falls off for the relatively large amounts of powder put in, you are reaching max pressure for that powder/cartridge combo. I hope that explains it well enough. - Dan

Dan,

Thanks. That type of info is what I'm looking for.

A couple of questions though. In your equation (which X barrel length/volume = velocity), what volume are you talking about? Barrel volume, charge volume, or overall case volume? Also, what are the units used for these calculations? Do you know of any web sites that go into detail on this?

I'm just curious on this. It would be interesting to see how the numbers play out. Also, is there a rule of thumb addressing load efficiencies when you start seeing the velocity differences decrease as more powder is added? I.E. when the velocity differences reach 30 fps or less between say 4 different loads, you have reached an inefficient point for that particular powder.

Jethro, et al,

My best groupings for the .300 RUM ahve come from H-4831 SC @ 89.7 gr, using 190 gr. MK (copper)...3213 fps. I have a 1.350" (od) Hart SS barrel, 1:10 28" LOA. I tryed Moly coated 190 MK and got all sorts of erratic chrono readings and some weird case denting (came from too-low a pressure)...So ,as with the above entries, recommend you change powders and see the potential of the .300 RUM. Take it from a formerly die-hard .300 WM shooter, the RUM is a better shooter, especially at longer ranges!

Good luck!

JW

Barrel volume. - Dan

jethro,

I can't offer an "engineering" type answer but can offer something I have found, but don't know the reason.

Much of my loading over the years has involved reduced loads with powders that are too fast for optimum results. Example being Varget in the 300 Win with 150 grain bullets. That would be simlar to using 4350 with 180s in the 300 Ultra.

Two things freqently occur. If these "too fast" powders have the load increased to the point where acuracy falls off, quite often just before that point the accuracy is often the best you will see in the calibre. I guess that is what Nosler found with 4350 and 180s in the Ultra

The second thing that often happens is that accuracy falls off at lower pressure than is the case with powders of normal or optimum burning rate for the caliber.

So this can mean that 82 grains of 4350 with the 300 Ultra has lower pressure than the 70 grains with the 300 Win.

The faster the powder is compared to the optimum, the more the above seems to happen. For example I have used a lot of H4227 Extreme with the 220 grain Hornady in the 375 H&H. That will shoot extremely well from match barrel from about 35 grains being at the 1.75" grouping and the grouping shrinking to less than 1 inch at around 39 grains through to about 42 grains, then the groups usually start to open. However pressure is very low when the accuracy falls off and velocity is around 2100 f/s. You would find that a 375 Winchester Big Bore would do that with not much more than 30 grains of powder.

How is that for an explanation at 3.40am Sydney Australia time on January 1 2003

I am not sure what we are fueled with here at the moment but I think it is like Bullseye.

Happy New year to you in what..about 12 hours if you are on the East Coast.

Mike

[ 12-31-2002, 20:57: Message edited by: Mike375 ]