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The 7mm SAUM

by G&A Staff   |  June 28th, 2017 0

7mmSaum_F
By Caylen Wojcik

When I began my search for a multi-purpose, long-range cartridge, I wanted it to be capable of playing dual roles as a tactical competition caliber as well as an effective long-range hunting caliber. Obviously, there are plenty that goes into that equation: ballistic efficiency, projectile availability, barrel life and reasonable recoil. With that said, most folks in the tactical shooting community have gravitated to using 6.5mm and 6mm, as they check all of those boxes nicely.

However, for a heavier-hitting bullet to fill the hunting role, most shooters jump right into the .30 caliber offerings, which have ideal characteristics except one: stout recoil. Besides a few F-Class competitors, it almost seems like the 7mm has been forgotten in the world of long-range shooting. That’s unfortunate, as it can offer the best bang for your buck as an effective and efficient long-range performer due to exceptional bullets with outstanding ballistic coefficients (BC) and muzzle velocities.

GOING 7
My choice to go with the 7mm came from a conversation with a competitor talking about how impressed he was with his 7 Winchester Short Magnum (WSM). I was already on the fence with a new middle-ground caliber, and shortly thereafter I ordered a barrel and hit the books for some research. I wanted a short action to save on weight for hunting, so that immediately drove me to the

From left to right: .260 Remington, 7mm SAUM, .300 Winchester Magnum. The 7mm SAUM offers arguably better performance than the .300 Win. Mag. in a package almost as small as the .260 Rem.

From left to right: .260 Remington, 7mm SAUM, .300 Winchester Magnum. The 7mm
SAUM offers arguably better performance than the .300 Win. Mag. in a package almost as small as the .260 Rem.

7 WSM. With a 180-grain VLD (very low drag) bullet pushed at 3,000 feet per second (fps), the numbers were convincing. When I shot a WSM, I was impressed with the mild recoil but received a rude awakening when sourcing brass. It was offi- cially unobtanium. One would have more luck sourcing unicorn tears.

I had no desire to play the neck-down game with .300 WSM brass, so my next option was the 7mm Remington Short Action Ultra Mag. (SAUM). I cut straight to the chase and sprung for Norma brass, which proved to be an excellent decision. Norma brass is amongst the best avail- able and is incredibly consistent with zero cull rates. Remington makes SAUM brass, and I’ve heard that it can be quite consistent if the necks are turned and you’re willing to weight sort the brass. Norma brass is pretty spendy, at about $1.50 a case, but I don’t have to tin- ker with case prep. Nosler also produc- es SAUM brass, but it’s almost $2.50 a case.

NUTS AND BOLTS
JD Thomas of High Speed Shooting Systems built the rifle on an American Rifle Company (ARC) Mausingfield ac- tion. I used a Proof Research all-steel 26-inch heavy Palma contour barrel spun at 1:8-inch twist attached to the action with a Savage barrel nut.

The ARC Mausingfield is a work of art, blending the best features of three actions into one. A Remington 700 footprint is the foundation for this engi- neering marvel. A Mauser positive feed and extraction claw and a Springfield ’03-style ejector make the Mausingfield as reliable as they come. An interchange- able bolt head allows for a multi-caliber system. The interchangeable design also provides an enhancement of the already well-renowned Mauser extractor. The Mausingfield uses an extractor collar that is a solid ring design instead of a flexible collar. The toroidal (donut shaped) bolt lug design ensures that both lugs consis- tently engage the receiver when the bolt is closed. It’s silky smooth and the bolt runs like it’s not even there. I dropped the package into a Kinetic Research Group (KRG) Whiskey-3 Chassis and topped it off with a Kahles K624i 6-24X scope with MSR-K reticle. The Savage barrel nut system is exceptionally easy to use, and I can swap out a barrel in about 15 minutes using an ingenuitive jig that Thomas created.

One of the benefits of working with a local gunsmith was the ability to control and access the project. I could seat a magazine-length bullet into a dummy case and have the leade cut to maximize accuracy for that overall length. I don’t like to jam VLDs under any circumstance, and this chamber ended up shooting them extraordinarily well at .045-inch jump. I elected to use Alpha Industries’ Type 4 magazine designed for the .300 WSM-sized case. These mags are rea- sonably priced and ran flawlessly with the Mausingfield/Whiskey-3 combo.

The 7mm SAUM has a reputation for being easy to load using medium to slow burning powders. I used two powders: H1000 and H4350. The 63.9 grains of H1000 gave me what I was looking for with both accuracy and velocity. It printed groups of .2 to .3 MOA and a conser- vative 2,920 fps with standard deviation (SD) at 6 fps. I was able to get dialed within 46 rounds of load development. That’s pretty simple, so the SAUM’s rep- utation holds true. The 180 VLD doesn’t take up too much case volume when loaded to magazine length, either. With about .09-inch of bearing surface below the neck/shoulder junction, there’s plenty of space in the case to spare. Other notable powders to look at are Reloader 22 and Hodgdon H4831SC.

GOING HOT
The 7mm SAUM is an impressive long-range performer. One of the main benefits of the 7mm is the wide variety of heavy bullets with high BCs and low form factors, both desirable for efficient trajectories. I chose to run Berger 180-grain VLDs as the do-it-all competition/hunting bullet. Looking at a 1,000 yard firing solution with 5,000-foot Density Altitude (DA), I would be at 6.8 mils and

The 7mm SAUM is an ideal cartridge for long-range competition and long-range hunting.

The 7mm SAUM is an ideal cartridge for long-range competition and long-range hunting.

needing 1.3 mils for a 10 mph full value wind. In order to obtain that performance from a .30 caliber, I would need to jump into the .300 Win. Mag. with either the Berger 215- or 230-grain Hybrid and push them at maximum pressures. Both of those calibers have significantly higher recoil, and the gains are only .1 mil less for the same 10 mph full value wind.

The next option is the .300 Norma Mag., which offers even better performance than the .300 Win. Mag., but again, that’s too much recoil in a competition scenario.

With the above velocities for my 7 SAUM load, the math is fairly simple for a quick range card in your head. If we take our range to the target in hundreds of yards, then subtract three from that number and an additional .2 from that, we get our elevation hold in mils. For example: 800 yard target = 8 – 3 = 5 – .2 = 4.8 mils elevation hold. The constant of -3.2 from our range in hundreds of yards works pretty well from 600 to 1,300 yards. Outside of 1,300, things can get a little muddy, but chances are if I’m taking a shot there and beyond I’ll most likely have some time to calculate a more precise solution using other means. Inside of 600 yards, use a constant of -2.5 to come up with our hold in mils.

GOIN’ WITH THE WIND
As with most of the 7mm heavies, the 7 SAUM is very efficient in the wind. The 180-grain VLD at the above velocities shows a 48-inch drift at 1,000 yards in a 10-mph full value wind. Looking at this from a different perspective, that’s 4.8 inches per mph of wind. Once we start looking at the wind from this point of view, it can give us an immediate indication of how accurate we need to make our wind calls for a given target size.

7mmSaum_4

Click on chart for a full size image.

 

On an 18-inch wide target at 1,000 yards, I have to call the wind within 1½ to 1¾ mph of its actual velocity to get a hit if I’m aiming at the center of the target. Another way to look at it is in mils, which would mean that at 1,000 yards, I have 1.3 mils of wind drift for 10 mph, or .13 mil per mile an hour. We can use a simpler method to get fast and accurate wind holds. Running some numbers, I can identify that if I take my range to the target in hundreds of yards and use a wind speed constant of 8 mph (full value), my mil holds line up pretty well with the range in hundreds of yards. For example: 800 yard target = 8, and a full value wind of 8 mph means I 7mmSaum_5need a wind hold of .8 mils. The real number is .75 mils, but, hey, what’s .05? This hasty wind hold method works well out to about 1,400 yards with my 7 SAUM, and the 8 mph constant will put my wind holds consistently .1 mil under the actual values, which is close enough for me.

So far, I’m very pleased with the 7 SAUM’s performance. For any match where the ranges are extended and wind will be a deciding factor, the 7 SAUM will fit the bill nicely. Does it have more recoil than a speedy 6.5 or 6? Of course it does. And if the match you’re shooting requires a fair amount of multiple target engagements, managing the recoil of the SAUM can be work and may not be the ideal choice, especially in unconventional shooting positions.

I would encourage any long-range enthusiast to take a hard look at the details of the 7mm. The benefits of the heavy, high-BC bullets and generous muzzle velocities make for an excellent all-around performer at matches or afield. The 7 SAUM is also easy to load, which means less time at the bench and more time learning and having fun on the range.

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