Those somewhat lighter bullets still carried enough weight for deep penetration. Nosler 162-grain Solid Base bullets from my 7 mm Rem. Mag. punched clear through elk, while 180-grain bullets from my .30-’06 Sprg. usually stopped under the hide on the far side.
Back then the Nosler Partition was about the only controlled-expansion 7 mm bullet. Today sporting goods shelves are stacked with bullets that limit frontal upset to retain a bullet’s shank for deep penetration at the 7 mm’s often high impact velocities. Take your pick of bullets with jackets that mostly or fully separate their front and rear cores such as the Speer Grand Slam, Swift A-Frame and of course the Partition, jackets welded to lead cores such as the Hornady InterBond, Nosler AccuBond and Swift Scirocco or bullets composed of a homogenous solid like the Barnes Triple-Shock X-Bullet, Hornady GMX and Nosler E-Tip.
My 7 mm Rem. Mag. was great and dandy back when I worked at the mill. Certainly it killed elk better than my old pokey .30-’06 Sprg. But in 1985 I bought a chronograph. The 160-grain bullets that I thought were leaving the muzzle at 3,000 fps and faster actually flew not much over 2,700 fps with a maximum charge of IMR-4350. A top weight charge of IMR-4831 fired 160s only slightly faster than 2,800 fps. Suddenly my old ’06 didn’t seem so pokey.
Since then, slower-burning propellants have been introduced that produce higher velocities in the 7 mm. Magnum and Reloder 25 send off 160s at slightly faster than 3,000 fps while Reloder 22 and 25 fire 175-grain bullets about 2,900 fps.
Loading The Original “Big Seven”
To start the reloading process I shot three 7 mm Rem. Mag. factory loads in Remington’s Anniversary Edition rifle. As the load table shows, they shot well; four, five-shot groups averaging as tight as 1.16 inches at 100 yards with velocities in excess of 2,900 fps using 160-grain bullets.
I took some measurements of five cases before and after they were fired and again after they were sized and fired a second time. Monitoring the case lengths, I found the case necks stretched quite a bit each time they were fired and sized:
Case Length Inches
New Unfired 2.490
Fired 2.495
Full-length sized 2.505 to 2.508
Trimmed 2.490
2nd Firing 2.495 to 2.497
2nd Full-length sized 2.502 to 2.506
Sizing the case necks only enough to hold a bullet might reduce this stretching. But after one or two firings brass will fail to spring back enough and a cartridge loaded with the cases will fit in the chamber only if you lean on the bolt handle like a pry bar. So pay attention to case lengths.
I also took measurements of loaded cartridges. After loading 10 cartridges apiece with Barnes Tipped Triple-Shock X-Bullets and Hornady InterBonds I put the cartridges on an RCBS Case Master Gauging Tool to measure how precisely the bullets were aligned with the center of the cases. Alas, my 30-year-old seater die positioned bullets as much as 0.010 inches off center. Since the Case Master showed run-out of case necks was next to nothing, the seater die was the problem. Cleaning accumulated gunk out of the die helped a bit.
I switched to an RCBS Gold Medal seater die with a sliding guide that held cases tightly in alignment in the die and with the bullet seating stem. That reduced bullet run-out to 0.004 inches at the most. The bullets with this lower amount of run-out shot groups a couple of tenths of an inch tighter than bullets set crooked toward the rifling.
