Ballistics question

[Charger426]

Hi,
Just picked up a vintage box of Western 7mm Remington magnum cartridges.
175 GR. S.P.
The specs. on the back of the box state muzzle velocity 3070 fps and muzzle energy 3660 ft lbs.
This seem higher than any stated ballistics charts I have seen.
Is this to be expected for this cartridge?
I have 20 other boxes of 7mm cartridges but none of them give the specs.

 

[jmr40]

I think that is optimistic to say the least. My load manuals show 2850-2950 for 175 gr bullets and the real-world speeds won't be that fast. Sometimes back in the day cartridges were loaded faster than today. But more often the speeds were overstated. And 7mm Rem mag is one of those cartridges that often comes up short of advertised speeds once shot over a chronograph.

I had one until I bought a chronograph. On paper it looked pretty good, but once I found out the actual speeds, I was getting I sold it. My 22" barreled 30-06 was shooting the same bullet weights just as fast, or even a little faster, than the 24" 7 mag.

 

[Charger426]

Ya,
I thought the values seemed high.
Maybe Winchester was trying to out do Remington in the ammo dept.
Is this box before the 300 WM came about?

 

[JCSC]

I think most of the box data is compiled from a 26” barrel in optimal conditions. Rarely see that same performance on paper.

 

[Riomouse911]

I think a lot of pie fell out of the sky for ammo makers once chronographs became common and folks started comparing the published specs with real world numbers. It seems like just about every cartridge seemed to drop several hundred FPS off printed velocities between the 1970’s and now.

Of course some are still inflated, as .30-30 numbers are still 24” test barrel numbers and the vast majority of them are 20” and shorter. So, they’re always about 100-150 fps slower than advertised.


Stay safe.