<P> The 7mm Remington Ultra Magnum or 7mm RUM is a 7mm rifle cartridge introduced by Remington Arms in 2001 . </P> <P> The 7mm RUM was created using the . 404 Jeffery case which was also used to develop the . 375 RUM . 300 RUM, and . 338 RUM . By necking down the . 300 RUM to suit the . 284 or 7mm projectile, Remington produced a non-belted case with a head diameter that is somewhat larger than belt diameter of original belted numbers . The resulting case has significantly more capacity than any conventional belted magnum . Compared to the 7mm Remington Magnum, top 7mm RUM loads deliver 25% more energy at 300 yards . Such performance demands a price and in this case, that is a large muzzle blast, sharp recoil and short barrel life . </P> <P> The 7mm Ultra Magnum boasts the largest case of any commercial 7mm cartridge . </P>

Difference between 7mm mag and 7mm ultra mag