Loading Remington's 7mm Ultra Mag: Petty tests Hadgdon's loading data for the hot new 7mm Ultra Magnum

Guns Magazine, Feb, 2002 by Charles E. Petty

Ever think about launching a 7mm bullet at 4,000 fps? That isn't doable yet, but we sure can come close. In the new 7mm Remington Ultra Mag., Hodgdon's loading data shows 3,800 fps with a 100-grain Hornady hollowpoint. That's faster than the .22-250 with a bullet that's half the weight!

Any time a new cartridge is introduced, I get letters wanting handloading data. Although I can understand the undeniable rush for data, the fact is that nobody outside the factory has guns or brass yet. I guess the interest, must be purely academic, or, who knows, maybe some people just collect data. But there is no denying that as soon as the stuff is available, handloading will begin.

I've found that developing data on a cartridge which is simply a variant of one I'm' familiar with isn't too hard. But when it's a brand-new cartridge, patience is required. And when you consider the popularity of lawsuits today, the last thing anybody wants to do is publish a handload that hasn't been tested by a laboratory with the proper testing equipment.

A couple of years ago, Remington introduced the .300 Remington. Ultra Magnum. This is one big sucker and is based on a case that resembles the .404 Jeffrey. You should expect to buy your powder in bulk to feed this big boomer. Last year Remington introduced a variant of the .300: the 7mm Remington Ultra Mag. Powder sales will spike up again, but, as is so often the case, one half of the equation lags behind the other. In this case I had the test rifle a couple of months before the ammo was available.

Then a fax came in from Hodgdon with loading data for the 7mm UM. Hodgdon must have a great relationship with Remington to have developed this data so early on. And it is noteworthy that no other data has appeared over the months that I've worked with this project, although it may well have by the time you read this. My compliments to Hodgdon for making this information available.

No Brass -- No Problem

Of course I didn't have any brass, and shooting enough factory ammo to get some is an expensive and possibly painful proposition. So I did what any good boy. scout would do -- I improvised. The 7mm Remington Ultra Mag. is, after all, a necked down .300 UM; and I had plenty of those cases. And this is one of those circumstances where the only change between the two is bullet diameter. There also wouldn't be an effect on powder capacity because the shoulder remains in the same location. So we were shooting long before we received any factory ammo.

The 7 mm Ultra Mag is a high pressure cartridge with a maximum of 65,000 psi. This is not something to be trifled with, and I deliberately elected to limit work to Hodgdon powders because of the available pressure-tested data. It was also necessary to, limit the bullets used in the test. To its credit, Hodgdon tried just about every known weight from 100-grain up to 175grain. (The data is available from Hodgdon, or via its Website.)

I chose to follow the factory's lead here and avoid the heavier bullets. At the time of this writing there are two factory loads: one with a 140-grain Nosler Partition bullet and the other with Remington's 140-grain CoreLokt. Velocity for both is advertised as 3,425 fps, and my chrono showed 3,405 fps. As a point of comparison, this is 100 fps faster than the 7mm STW with the same bullet weight.

Size Mailers

The test rifle is a Remington Sendero SF with a 26-inch barrel. The barrel length is important only in that it complicates comparison of factory and handloaded ammunition. Remington's catalog doesn't state the length of its test barrel, but Hodgdon's is 24 inches. Because I overlooked this discrepancy, I wondered at first why I was getting higher velocities... duuh. Achieving higher than published velocities is something that just doesn't happen very often. Depending on the powder and other variables, my 2-inch longer barrel could account for velocity differences of 50 to 100 fps.

Depending on bullet weight, Hodgdon used five different powders in developing its data, which are all in the slow range: (in order of burning rate) H4831, H4350, H 1000, H870 and 5OBMG. To simplify things a little, I used three: H4831, H1000 and H870.

Hodgdon's starting load in this caliber is usually 6 grains below the maximum. So, again to simplify a bit, I loaded three charge weights in 2-grain increments with the heaviest being the maximum. This verities that everything is progressing in a linear manner. I chose 120- and 140-grain NosIer Ballistic Tips and Speer's 110-grain TNT.

Any time you do these lengthy tests, shooter fatigue is an issue. And with something carrying substantial recoil, abuse is also a factor. This went a lot quicker thanks to Bob Maddox, who shared the shooting/chronographing chores. Since I didn't have access to pressure-tested data from any other source, I chose to work exclusively with Hodgdon powder. As others publish data, I will be able to do more testing -- but I won't print loads that can't be traced to some verifiable pressure test data. Even so, Hodgdon has four or five powders that are quite suitable for the supermagnums.