338"s; Laupa or Ultramag?


January 21, 2007, 11:48 PM
Have a 338 ultramag and was looking at some reloading info, what's available:banghead: to me, and it SEEMS that the ultramag undercuts the 338 laupas' case capacity. Anyone know enough to enlighten me on this? Just curious- is it just me, or does Remy seem to try and edge out other mfgs with their ultramags? Good marketing ploy, but they don't even market it:rolleyes: as such if it is indeed true. Also, anyone know about the 300gr serria bullets for the 338? Will try a box, just will be 3 months (minumun) before I can get around to this experiment. Trying to get a 750yard target gun - that's the length of my available ( friends) target range.

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January 23, 2007, 08:17 AM
I don't have any data on the case capacity of the .338 Lapua. I do have a data listing for the .338RUM at 6.61cc.

I don't think that Remington was particularily targeting any one cartridge in particular when they developed the UltraMag series of cartridges. They were just tapping into a market for large capacity cartridges/rifles. With the design parameter limitations of existing actions, the UltraMags are about as big as you can get. It is only slightly below the .30/378 Weatherby and matchs or is only 90-120fps slower and a bit more efficient, if that term can be applied to a cartridge in this genre.

If I were looking to build a long-range match rifle, I'd go with the .300 RemUltraMag. Dies, cases, and component bullets are much more available and somewhat less expensive than a highly proprietary cartridge like the .338Lapua.

I have one (.300RUM) in a Savage M110. It is fairly accurate, about what you'd expect from a light-weight barrel sporter. The cartridge actually behaves much like a "over-grown" .223 rather than some "ragged edge" fire-breather like the Weatherby's have been loaded too.

I regularily see 3,300+fps with 180gr bullets and ".308wcf" level pressures and .308wcf type accuracy. I have seen 3,500+fps readings on the chronograph, but these were at or perhaps slightly above nominal maximum pressure levels, and accuracy was beginning to suffer slightly.

With the large number of available heavy match bullets of very high ballistic coefficency and lower cost due to lower weight and higher production volumn, I'd definintely go with the .30 bore over the .338. (But then, I'd probably go on down to the 6.5mm personnaly).

The only reason I'd see going to the larger bore is to gain bullet mass for greater energy at target ranges. With a paper target, energy is not a consideration, only bullet flight time and wind drift/wind sensitivity.

My .300RUM has shown a marked preference for a quantity of WC-860 surplus .50BMG powder that I purchased in bulk for $25 for 8lbs !!
It has also shown a preference for the Remington 180gr Corlokt bullet giving MOA accuracy. Inexpensive "big cartridge" shooting !!!! Bullet has shown capability of withstanding these velocities on smaller biggame also.

I hope my "ramblings" have been of some benifit.

Zak Smith
January 23, 2007, 11:18 AM
The two cartridges have almost the same case capacity (within 2%). The Lapua's max pressure allowed is slightly higher than the RUM. The Lapua has stronger brass. The RUM's case is longer, while the Lapua's is wider. Brass quality is better in Lapua. The Lapua can seat bullets out further in the same action length.

ETA- the rest benefit of these high capacity 338's is the ability to shoot the high-BC heavier bullets at fast velocities. Common bullets are the 250gr Lock-Base, 250gr Scenar, and 300gr SMK.

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