Remington Ultra Magnums (What You Need to Know)

Updated on December 11, 2019
LJ Bonham profile image

LJ Bonham is a semi-subsistence hunter, hunting magazine editor, and firearms enthusiast who lives in the Rocky Mountains.


Okay, I admit it. I didn’t look forward to this assignment: write a few words about Remington’s famous Ultra Magnum rifle cartridges. These are, with little doubt, amongst my least favorite hunting rounds. I’ve always thought they went a bit too far down the “more is better” rabbit hole. However, I’m a professional gun writer. I can do this. I think.

My preconceptions aside, the RUMs, as shooters most often refer to them, look fine on paper. Who could quibble with monumental velocities and the ability to put the hurt on game out to 1000 yards and beyond? They deserve a fair hearing, if nothing else.

The Remington Ultra Mags debuted in 1999 with the .300 RUM. Then its brethren appeared (in order): .375 RUM, 7mm RUM, and then .338 RUM. Each purported to open new and wondrous realms for shooters with class-leading velocity and energy—although this has proven disingenuous in some cases.

Not So "Ultra" (The RUM Dark Side)

The RUMs met with the usual fanfare upon their introduction, but as shooters lived with these fire breathers, a darker side emerged.

A major complaint is throat erosion. Whenever a rifle cartridge is fired, the gasses generated by the burning powder are so hot, they turn the steel in the barrel’s throat (the area between the chamber and the rifling) from a solid into a plasma for a millisecond or two. In short, the hot gas jet becomes a plasma cutting torch. The throat cools back into solid steel once the powder column burns itself out, but it loses material in the process. This is throat erosion. The more powder in the case and the longer the burn duration, the more steel it takes with it out the muzzle.

The smaller caliber RUMs are overbore in the extreme. Overbore is the ratio between a cartridge’s neck diameter and powder capacity. The RUMs have enormous cases, necessary to generate ultra-high velocities, but the tremendous gas volume produced upon firing must squeeze through narrow necks in the 7mm and .30 caliber versions which makes for a tremendous plasma torch effect. This wears out a barrel in short order.

Another significant problem is heavy recoil. Yes, RUMs have almost flat line trajectories and hit hard at long-range, but they pound the shooter in the bargain. Heavy recoil has a negative effect on the ability to shoot well. It’s hard to concentrate on fundamentals when you expect to get smacked with a ballpeen hammer every shot.

Then there’s Remington’s dubious decision to use a rebated case rim. To avoid the need for an all-new, dedicated bolt for RUM rifles, Remington kept the RUM’s rim at the standard H&H derived magnum diameter, .534-inches. This is narrower than the case body’s .550-inches. Rebaited rims over the years have acquired a poor reputation for feed reliability. While Remington’s engineers seem to have dealt with the problem, it does give one pause with the two RUMs intended for dangerous game hunting, the .338 and .375. A dangerous game rifle cannot have any potential, no matter how remote, it won’t go “bang” every time.

Ultra Mags' original home: the controversial Remington Model 700
Ultra Mags' original home: the controversial Remington Model 700 | Source

.300 RUM

This standout is the original and most popular Ultra Magnum. Remington paid close attention to developments in Canada and acquired cases based on the .404 Jeffery from North American Shooting Systems. After extensive study and refinement, Remington believed they had a winner.

Until the .300 RUM appeared, the world’s shooters depended on the .300 Winchester Magnum to carry bad news to far off critters such as mule deer, elk, and African plains game. The .300 Weatherby had a bit more zip, but the Win. Mag. had the sales crown. Remington called and raised both competitors with the Ultra Magnum.

The .300 RUM in factory guise will catapult the ubiquitous 180 grain bullet 200 – 300 fps faster than the Winchester. However, .300 Weatherby shooters wonder what took Remington so long to catch up as the RUM duplicates the California hot-rod which appeared 45 years earlier.

Where the .300 RUM earns its salt is with ultra-heavy for caliber bullets: 200 grains and up. For example, factory loads dispense super-aerodynamic 210 grain projectiles at around 2920 fps. Compare to the Weatherby’s 2825 fps and the Win. Mag.’s (200 grain) 2800 fps.

Trouble is, when you step up to these bullet weights in order to gain higher ballistic coefficients, you pay the price in recoil. An eight or nine pound .300 RUM rifle will whack your shoulder with the same force as a .375 H&H in a ten pound gun. Not conducive to long stints on the range to maintain proficient marksmanship. Best advice, have your chiropractor on speed-dial.

.300 Remington Ultra Magnum. Note the rebated rim.
.300 Remington Ultra Magnum. Note the rebated rim. | Source

.300 RUM Doing What It Does Best

.375 RUM

The second cartridge in the RUM family is the .375. Another attempt, it seems, to out Weatherby, Weatherby. The .375 RUM, like the .375 Weatherby, answers a question few people have asked. For over a century, the versatile .375 H&H Magnum has served hunters on every continent with distinction and graceful power. There is no real need to drive bullets this size and weight any faster, as a brown bear, Cape buffalo, elk, or elephant will tell you. Yet, there’s always a certain customer out there who must have the fastest rifle in a hunting camp, and Remington is determined to feed their egos.

Nominal ballistics for the .375 RUM are a 300 grain bullet driven at 2900 fps which pips the .375 Weatherby by 100 fps and the .375 H&H by 400 fps. Yippee. It’s still nowhere near the deranged .378 Weatherby, though.

Sales figures tell the story with this over the top RUM. Mega-retailer, Midway USA, for example, stocks 24 loads for the .375 H&H, a mere two for the Remington, and a solitary one each for both Weatherby bruisers. Yup, nobody thinks the massive recoil is worth the increased velocity. Most who need more power than a .375 H&H just ask the gun bearer for their second rifle chambered in something which starts with a “4,” or perhaps a “5.” In short, the faster .375’s are superfluous.

Author believes the .375 RUM is an unnecessary improvement on the .375 H&H Magnum pictured here.
Author believes the .375 RUM is an unnecessary improvement on the .375 H&H Magnum pictured here. | Source

.375 RUM: More Recoil Than It's Worth

7mm RUM

The 7mm RUM arrived in 2001. It promised a new era for long-range hunters and competition shooters. Imagine sleek .284 caliber bullets launched at 200 or even 300 feet per second faster than the world’s most popular 7mm, the 7mm Remington Magnum (just plain “Magnum,” thank you—no “Ultra”). How could any shooter turn such a recipe down?

As it so happens, shooters couldn’t, and hadn’t needed to since the 1940s when the 7mm Weatherby debuted with similar ballistics. Nominal 7mm RUM specifications for factory ammo are a 150 grain Remington Core-Lokt bullet delivered from the muzzle at 3110 fps with 3221 ft-lbs energy. Nosler offers a heavy for caliber, 175 grain AccuBond Long-Range bullet at 3040 fps and 3590 ft-lbs. Heady stuff which makes the 7mm Rem. Mag. look quaint. The 7mm Weatherby, however, exceeds the RUM upstart: 150 grains at 3300 fps and 3627 ft-lbs; 175 grains at 3070 fps and 3662 ft-lbs. Well played, Weatherby.

Another 7mm RUM rival is the 7mm Shooting Times Westerner. It launches a 160 grain pill at 3075 fps with 3358 ft-lbs; 175 grainers pound forth at 2900 fps/3267 ft-lbs. A bit more than the 7mm Rem. Mag., but without the RUM’s or Weatherby’s recoil and powder appetite.

To make matters worse for Remington’s darling, the 28 Nosler has arrived (as if we needed yet another 7mm magnum). It turns in almost identical numbers to the RUM, but uses a shorter, more efficient case design which fits into standard (.30-06-length) actions.

While the 7mm RUM has impressive performance on paper and delivers the goods on the range and in the hunting fields, it does so at a rifle’s expense. The 7mm RUM’s overbore ratio is exceeded only by the .30-378 Weatherby.

Few other cartridges can match the 7mm RUM for shear destructive power when it comes to throat erosion. Many rifles chambered for the round are junk in 600 - 800 rounds, less if the shooter doesn’t practice good barrel protective protocols at the range.

The best way to sum up the 7mm RUM is as a first rate rifle destroyer which gives little down-range advantage over other, more efficient 7mm magnum cartridges. No wonder it is the least popular RUM.

Despite The Problems, 7mm RUM Gets It Done

.338 RUM

At first blush, the .338 RUM seems destined to fill the same role as the .375 RUM: a round which has no real purpose other than braggadocio. This last RUM, introduced in 2002, looks for all the world as a belated attempt by Remington to steal some thunder away from the stalwart .338 Winchester Magnum, and cut into the limited, but fanatical, market share Weatherby and Lapua enjoy with their .338 offerings. In this it does succeed—to a point.

Face it, .338s have never had the same shooter acceptance in the U.S. as the .30 calibers. Many think .338s cross the recoil line, and unless they intend to hunt Alaska, they’ll stick with the smaller bores, thank you.

The long-range shooting cult has changed some minds about .338s, though. This caliber offers spectacular ballistic coefficients and sectional densities. These bullets fly flat, retain bone breaker energy down-range, and penetrate deep. Just the ticket for the largest non-dangerous game in the Western U.S. or Africa, and Alaska's big bears.

Factory .338 RUM loads push 250 grain bullets at 2850 fps, or so, and mega-slippery 300 grainers at 2600. This causes many a fevered dream for long-range hunters. The .338 Win. Mag. can’t compete with these .338 Lapua league numbers. It does beg the question whether the world needs this round which is still left behind by both the Lapua and Weatherby’s fierce .338-378. A hunter who is a skilled stalker is better served by the .388 Win. Mag., in my opinion, which fits in standard rifle actions. The hard-core long-range crowd wants the velocities offered by the Weatherby and Lapua. The .338 RUM lingers in the marketplace in all likelihood as a reasonable compromise between those two extremes.

Left to Right: .22 LR, .30-06 case, .338 RUM
Left to Right: .22 LR, .30-06 case, .338 RUM | Source

Final RUM Thoughts

The Remington Ultra Magnums miss the mark in so many ways. They chew up rifles in short order; have questionable rebated rims; pound shooters with more recoil than required for any given job; are seldom chambered in any rifle other than Remington’s tort provoking 700 series; and use way more powder than needed. Plus, they often don’t provide much more performance than the time tested Weatherby cartridges. The market has spoken, all the RUMs, save the .300, are on life support and the .300 Winchester Magnum still outsells the .300 RUM three to one.

I won’t argue with anyone who thinks a RUM fits their needs—it’s still a (somewhat) free country. However, if I’m in the mood for a magnum, I’ll stick with the ones which have dropped game for decades, if not centuries, and call it good.

© 2019 LJ Bonham


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