Talk:.300 Remington Ultra Magnum

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[edit] Ballistic performance and test barrel length

Due to this cartridge very large case capacity in relation to its bore size a 24 in (609.6 mm) long barrel as used in the “info box - ballistic performance” section gives not the most realistic examples of the .300 Remington Ultra Magnum or its ballistic twins ballistic potential, though the stated performance figures in this article are very credible. Barrels that are too short in relation to the employed cartridge will produce sub standard muzzle velocities, unnecessary recoil and lots of muzzle flash, smoke and report. The main cause for these effects is unburned propellant. Custom made rifles for these kind of super magnum cartridges generally sport 762 mm (30 in) or longer barrels to take advantage of the ballistic potential of these overbore cartridges. Francis Flinch 13:03, 3 September 2007 (UTC)

Despite the long barrels than can be created, the goal of the infobox isn't to show the max that could be done, it's to show typical realistic usage. No standard rifle manufacturer delivers .300 RUM in a barrel longer than 26". If you want to mention that better ballistics could be achieved in a longer barrel, feel free to add it to the article, but recognize that this is true of almost every cartridge in existence. Powder burn efficiency is a factor of not only cartridge size, but shape, neck diameter, barrel length, powder type, powder burn-rate, bullet weight, temperature, etc. I don't see any reason to bear all these facts out on every .30 caliber magnum cartridge page. Arthurrh 17:55, 7 September 2007 (UTC)

I have to agree with Arthurrh. I would go one step further and delete the Accurate Powder information. Not that the Accurate Powder company is incorrect but that there are many different powder companies that publish .300 RUM loads. I would prefer to use Reminigton published loads for velocity and muzzle energy. Having said that, Remington uses a 26 inch test barrel for .300 RUM loads.

I would also like to remove the part about the .300 RUM being more efficient than the .30-378 Weatherby. See below.

[edit] Efficiency

A common misconception is that cartridge (powder) efficiency or bore to cartridge capacity is lineal or proportionate. That is, if I use 10 percent more powder I should get 10 percent more velocity and/or muzzle energy. This is incorrect and will never happen between two separate cartridges of differing, bore, case geometry or capacity (all other things being equal).

The reason is because a 10 percent increases in powder is a 10 percent increase in energy. Energy is not proportionate like force. Energy is a function of the square; v². The square root of 10 is 3.2. Therefore a 10 percent increase in powder will tend to support a 3 percent increase in muzzle velocity. The muzzle energy is dependant on the weight of the bullet; the greater the weight the greater the percentage of increases in muzzle energy.

Now couple that with the fact the .300 RUM operates at a high mean chamber pressure than the .30-378 Weatherby Mag (65,000 and 63,800 PSI respectively) and on paper there is virtual no difference between the two cartridges.Greg Glover (talk) 01:14, 20 February 2008 (UTC)