7mm Rem. Mag. not living up to it's billing

Lefty Dick

Lefty Dick

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I bought a beutiful Rem 700, in 7mm. Rem. Mag. it's used but the borescope shows that the round count through it was quite low, actually the bore, and chamber etc. looks almost new.
Well time to do some load development with it. So I buy some factory fodder, to give a try, and holy crap 150's only clocking at 2920fps. The chronys bang on all the other rifles are clipping along at expected velocities. So then I crank out some pretty stout loads with 150's and IMR4831, depending on the manual your using it;s either 2 grains over max, or right at max. and gee whiz 2900fps???!!!.
So off I go and I buy some IMR 7828, and some H1000, really would have liked to try some RL stuff, but it's so on and off in supply I'll stick by IMR, and Hodg.
Ans I stoke up some 160's under both powders, I got some pressure signs with the 7828 and only got about 2780fps. Now I never reached any pressure signs with the H1000 but a top end load of it only cranked the 160's out at 2800fps. I'm gonna load a tad hotter with the H1000, but wow, is this rifle or barrel ever a dog.
Any suggestions, I'm thinking of chucking the 7mm Rem. Mag. I already have the 284Win, and really dont need the magnum performance, having a 300WSM already.
I thought of going right off the page and rebarreling it to this:



Thebigdick.jpg
 
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While I have owned a couple of 7Mags in the past, I didn't own a chrony at the time. Probably a good thing, cuz your observations are fairly common to other owners of this caliber. Even some loading manuals echo these findings. This is one reason the 270 or 280 is so attractive compared to the bigger magnum.






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The problem you are having is not unique. I'd be willing to go out on a limb and suggest that the tooling used to chamber and rifle your barrel was at the end of its life. I had a a .270 that could barely push 130's to 3000fps with all the 'appropriate' powders, Through a 24" barrel. The rifle shot wonderfully though, so it went on to kill 30 some big game animals. I've never seen the purpose of 'hot loads' (though I have pushed the limit a time or two) to obtain velocity when a properly made barrel will always obtain reasonable velocities in the cartridge choosen. If you don't like 2800fps with a 160gr bullet, rebarrel, or sell the rifle. The real question is how well does it shoot?:D
 
Quite honestly gang, I bought the rifle as project rifle.
I am only loading up for it because the deal came with dies, brass, and bullets. And I really suspected all the velocity hype about the caliber was mostly that. I just thought I'd throw my findings out there to see if I'm out in right feild or something.
It begs me to ask if the my findings are kinda typical, how do these guys claim the Rem. Mag. is the be all end all and so much better than their non belted counter parts?
After all I'm using 70 grains of powedr to drive a similarly weighted projectile get the same velocity as a "supposedly lesser" caliber does with 10 to 15grs. less of powder and 2" less barrel.
Some advantage eh.
 
Levi Garrett said:
Never chase Velocity with a Croney. :D Use it to help find an accurate consistant load. Want special effect fill the case with H870 , Got a good push , and quite a bit of smoke :D
Click to expand...

Too bad your 870 powder is discontinued or I would have given her a try.


And don't take my findings and questions as a slam against the Rem. Mag. it's popular cause it works. And of course that's all that really matters.

I doubt I'll keep the rifle as it is, simply because I already have a .284" bore already and it does all I want.

But I still like the banter and other peoples findings it keeps the board here lively and informative.
 
If you've got 26" of barrel, then I'd recommend you rebarrel to STW. Although the difference between STW and RM velocities are close _on paper_ (i.e. in load manuals...), in the real world of chronographs there's no comparison.

If you only have 24" or 22", then those velocities are probably all you can expect from the 7mm Rem Mag, and rebarreling to anything with more powder capacity is kind of a waste of time (at least with a 7mm bore).
 
I bought a chrony and took my 7mm to the range (26" shilen tube). 63 grs RL22 behind a moly Partition Gold did 2750 fps average :redface:

it took 70 grains of RL25 to get a 160 gr Speer bt to 2900 fps



in my 2nd 7mm Mag, a Rem 700 Sendero SF, 72 grains H1000 behind a 140 gr TSX would do 3205 fps. that is more like it :)
 
H870 gise good velocity and lower pressures, forr sure.
however, it is not ann extreme powder so I do not use it much, that and it is no longer available.

As an aside, to the "chrronograph syndrome" #### Robertson of Robertson Styk Bows, once had a Osage orange sinew backed bow that every one commented on how fast it was. he won many competitions with it, and killed some deer as well .
never gave it a thought until he decided to put it through a chronograph.
He stated in the article thhat he almost broke the danged thing trying to get it up to the "speed that it shoot be"!:eek:
The reality was that the bow SEEMED to be fast until it was chrony'd, then the reality set in that it was just a good bbow, and that speed does not kill, accurcay does!:D
I have always said, if a person wants to gget discouuraged, just put whatever you want through a chronograph to check its speed.
I use them for trying to find a consistant velocity, not a macimum velocity.

Most people it seems get too wrapped up in the speed thing....
Cat
 
I've got a 7mm Rem Mag Sendero that will push 150 gr. Nosler BT's very to 3,000 fps. using IMR7828. Barrel length is 26".

You've never once mentioned barrel length, so who knows? Might be all you're going to get. What time of year did you chronograph the loads at? Cold weather can and will affect your performance as you are no doubt aware.
 
US-869 is billed as the 'new' 870, and it's an 'extreme' powder as well.

I've never had problems reaching slightly over 3,000 fps with a 160 through a 26" barrel with max loads of 870
 
prosper said:
US-869 is billed as the 'new' 870, and it's an 'extreme' powder as well.

I've never had problems reaching slightly over 3,000 fps with a 160 through a 26" barrel with max loads of 870
Click to expand...

Is that a Hogdon powder?
I wasn't aware of it....
Cat
 
the 7mm Rem Mag is grossly underloaded in the current loading manuals....I had a 24" 700/7 Rem Mag that would do an honest 3325ish with a 139 Hornady...I had it up real close to 3400 but that load was a bit hot....load was from a Hornady manual from 1968.....IMR4350.....I won't tell you how much of it.........
 
The rifle is a BDL of 1974 vintage, 24" barrel.
After todays range session I am convinced as ever the factory barrel is a dog, I ran a 1.5gr. over max charge of H1000 under Speer 160's and got a wopping 2900fps.
I bought her for the action and well I guess I got the action.
Anybody want a real slow 24" Rem takeoff barrel, in 7mm. Rem. Mag.
Just kidding.
 
Lefty #### said:
The rifle is a BDL of 1974 vintage, 24" barrel.
After todays range session I am convinced as ever the factory barrel is a dog, I ran a 1.5gr. over max charge of H1000 under Speer 160's and got a wopping 2900fps.
I bought her for the action and well I guess I got the action.
Anybody want a real slow 24" Rem takeoff barrel, in 7mm. Rem. Mag.
Just kidding.
Click to expand...
Before you throw it away, how accurate is it?

Even if you are not getting the velocity you expect, if you are getting good accuracy, it may be a keeper?
 
I built a 7mmRM, 27" lilja barrel, Rem action, SAAMI spec chamber and it pushes the 175 SMK @3000fps with excellent accuracy. It likes Retumbo, I am 1.5 grains over the published max. load. ZERO pressure signs. You just have a dog of a factory barrel.
 
Lefty #### said:
The rifle is a BDL of 1974 vintage, 24" barrel.
After todays range session I am convinced as ever the factory barrel is a dog, I ran a 1.5gr. over max charge of H1000 under Speer 160's and got a wopping 2900fps.
I bought her for the action and well I guess I got the action.
Anybody want a real slow 24" Rem takeoff barrel, in 7mm. Rem. Mag.
Just kidding.
Click to expand...


As Hodgdon lists 2839 fps velocity for a maximum charge of 66 grains H1000 under a 160 grain bullet I fail to see what the problem is. You went over max and also got a velocity over the maximum.

How fast do you think a 7mm Remington magnum is supposed to be?
 
The 7mag is sometimes underloaded and sometimes has low powder charges since it has had some erratic pressure swings.

I routinely go over published data, to get to published velocities.:)

I don't do that wit any other cartridge. And I dont' reccomend it.
 
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