Home Forums Hunting & Shooting Long Range Hunting How come the 7 m/m

Where did you get that from?

Bob,

All pressure barrels used by SAAMI members are supposed to have chamber (and bore-groove) dimensions that meet SAAMI standards. In other words, I sincerely doubt the Nosler pressure barrel has an out-of-spec chamber throat.

I do know that for a few years after the 7mm Remington Magnum was introduced, demand for rifles was so high that some factory-rifle chambers varied considerably in dimensions, creating problems with SOME factory ammo.

I suspect the problem with your BAR (and others) might have been due to the factory using worn reamers, to keep up with demand. Unlike custom gunsmiths, factories use relatively inexpensive reamers that start out on the upper edge of SAAMI dimensions. As the reamers wear, they naturally cut smaller chambers. Factories normally quit using reamers when they wear to minimum SAAMI dimensions, but occasionally don't, for whatever reason. The neck dimensions can get pretty tight, especially with some brands of brass with thicker necks.

Brass that's been fired and resized a number of times also tends to develop "the dreaded donut" at the base of the neck, due to the thicker brass in the shoulder moving forward. This can cause pressure problems as well. I first ran into the donut back in 1974, when handloading for my first .243 Winchester, but it occurs in quite a few cartridges, especially when brass gets sized so the shoulder doesn't firmly contact the front of the chamber--common in belted cases.

Several reasons the 7mm RM is "underloaded," aside from the primary reason posted by Mathman, widely varying pressures:

The original factory loads were chronographed in 26" barrels, common back in 1962 when it was introduced, with a powder then unavailable to handloaders, IMR7828--which even today performs alongside newer magic powders.

This allowed the advertised factory velocities, but even then Remington factory ammo didn't quite make them, according to the Speer #6 manual, which contains a section on chronographed factory loads.

Also, the early reputation of the 7mm RM may not have been established because of actual ballistics. A lot of hunters and handloaders back then didn't have chronographs, so accepted the published factory and handloading velocities, yet their rifles still killed game with "reduced" ballistics.

A good friend bought one way back when, when everybody here in Montana had to have a "Big Seven," and according to the loading manuals his 160-grain handloads got over 3000 fps. It knocked the snot out of everything from deer to black bear to elk.

He bought a chronograph a few years later, long before most people did, and found out his magic handload got around 2700 fps, pretty much warmly-loaded 7x57 velocities.

But then, the 7x57 has been knocking the snot out of big game for a long time now!

Pressure isn't constant shot to shot. Modern testing equipment is able to show that the probability distribution of the pressure for the 7mm Rem Mag is spread out somewhat more than other cartridges. So the loading was changed to lower the mean pressure of the distribution enough so the area in the no go portion of the high pressure tail of the distribution became acceptably small.

Wait for the 7 creedmoor......

7 mm Rem. Mag. great cartridge , very accurate , very common cartridge for a magnum and the best part about buying and owning a 7mm Rem. Mag. rifle ammo is very easy to find/buy in north America including Canada and Alaska,that can be important. in a standard rifle chambered in a 7 mm Rem. Mag. with factory ammo you will never have a problem with pressures,as far as handloading a 7 Rem. Mag. if you follow safe reloading recipes in a new reloading book you won`t have any trouble either. my good friend who was a Ranger sniper for over 8 years until he was wounded that is his favorite cartridge the 7mm Rem. Mag. good luck with your choice ,Pete53

I can wait for a very long time.

I'll bet your English teacher probably suffered from pressure problems.

Rem Mag or Weatherby or RUM or STW are not talked about as good long range shooters? Are they just all old news?

What about the 7 SAUM?

... or the .280 AI?

Now you’re talking.

Have shot more than a whole fhuqking buncha both. Hint.
On a .532" 700 Donor...the 7mm Rem Mag simply STEALS the fhuqking show.
A Montucky 7 Whizzum with .796 BC 180 ELD's at 2900fps,reliably crushes alotta dumbfhuqktitude.
Hint...................(grin)