Home Forums Hunting & Shooting Ask The Gunwriters Why is the 7RM underloaded?

Question for the pros...

Seems to me that both factory ammo and loading data for the 7mm Rem Mag is a bit on the anemic side. Is this intentional? I found data dating back to the 70s and early 80s showing data for 160r bullets allegedly choreographed at 3100fps in production guns and 175s at 3000 fps.

IIRC wasn't the cartridge originally designed to push a 175gr at 3050fps?

I know I've pushed 160gr acubonds over 3000fps in my 24 inch 700 with zero pressure signs. What gives?

3308

Yep, been going on a while now. I have Hornady Vol II and most newer manuals don't touch it.
I've loaded 162s at 3160 and didn't blow up anything EVEN a case. imagine that !!

I'm not a pro, so I'll not try to answer your ??


Jerry

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.

Okay -

Many loads today 'hardly' beat the 270 Win velocity with "proportionate" bullets. That's my beef.!!


Jerry

here is the true answer LIABILITY no body wants to end up in court,over a rifle that blew up anymore so all ammo manufactures and books on hand loading have reduced the amount of powder used for their own law suit protection and i can understand why. my old hunting partner work for a ammo manufacture for 40 years and he spent plenty time in court and trying to solve problems from a rifle or pistol that had problems,most problems were from a hand loader using to much powder. that`s why velocities these days are lower > less powder,less pressure,less lawsuits its always about the money

I'm sorry, but I can't resist:

I want to see those choreographed bullets dance.

Ploughman; at 3100 fps, they are choreographing too fast for you to see 'em

Mine isn't.

Reloader 26 is the answer to all questions 7mm Remington Magnum with heavier bullets.
John

Id love some good data on the 160s and 175s. Ive had old timers tell me that the initial goal with the cartridge was to get the 175s over 3k...and they were able to do it roughly matching a wildcat that Warren Page was slaughtering animals with all over the world in the smaller RM case. I shoot and load for a couple of 270s and I agree 100% that with MODERN data...they have turned the 7rm into a 270 or 280. Not that thats bad company to be in...but with the bigger tank you should be able to smoke them.

Or retumbo, h1000,7977,8133

Mine isn’t either.

RL-26 is good stuff.

DF

Spot on.

Not worth the hassle...

Easier to just put him on ignore!

I finally got some 7977 and 8133 on hand. Looking forward to seeing if they'll perform as advertised.

Mule Deer has a very good history of the 7mm Rem Mag in the Gun Gack book. Happy Trails

Ok...just ordered the book. Ive been meaning to anyways...made for a good excuse

Ploughman
Most likely performing THE FIREBIRD.
Great choreography.

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!

You wouldn’t think that the physics involved with the pressure-spread of the 7 mm RM would be all that much different from, say, the 7mm Wby, which cooks the 175 along to 3k pretty easily. Is it the singular and famed radiused shoulder of the Wby?

I remember my first purchased lie-detector tried out on my favorite, hot-shot 140-gr, 270 load which thought to be about at the speed of light meandered along at about 2700 fps.

It’s interesting how much perception feeds into confidence or the lack thereof.

George,

The radiused shoulder of the 7mm Weatherby doesn't have anything to do with its comparatively consistent pressures. Instead it's the long "freebore" throat, which flattens the pressure curve.

The 7mm RM's throat is very short, and erodes pretty quickly. Both result in interesting pressure variations, both when the barrel's new, and as the throat erodes.