Home Forums Reloading Big Game Rifles 7 Mag stumper

O.K. I just returned from the range. My son-in-law's 7 Mag with a starting load of 65 grians of IMR7828 went 3,325 feet per second. The bolt was very hard to lift and the primer was gone. The book said it would go 3,005 fps.

My 7 RUM is shooting slower (120 TSX at 3,650 fps). When I started working up the load, they were going 3,750 fps.

We are using from the same can of powder. Any ideas?

What bullet weight?

He is shooting 140 Barnes TSXs.

back off .......
sumthin ain't right........


George

I concur with George, something is not right. I saw a load do this about 10 years ago in a 7 mag. In that case the bullet was seated out too far and was jammed against the lands, but it did not blow the primer. It showed high pressure and was a hard bolt lift. The primer was very flat and the case head had started to flow into the ejector plunger hole, which starts at around 71,000 psi. Primers blow and greatly expand the primer pocket at around 80,000 psi. I found this out many years with a 22-250, 70 gr Speer bullets, and W-760. I still have the cases in my collection of screw ups.
Good shooting!
Marcus.

Two things I would look into. Any chance the powder has been mixed with another powder (has your son been loading w/o supervision)? I've never seen powder mislabeled before but it may have happened to you. Have you weighed the bullets to see if 150 gr. bullets had been mislabeled as 140 gr.? A phone call to Barnes may be of some help.

1flier

Remember, all guns are an entity unto themselves...

did you work up to this load, or did you just pick the book max, load it and go to the range...

if so, there's your problem..

I'd love to know where the primer went... If it were me, I'd disassemble the loads with my kinetic bullet puller or collet bullet puller and weigh the components. I know we reloaders hate to admit that we mess up, but I found myself weighing charges one evening for my .260 Remington, I think it was supposed to be 45.3 gr of powder. Anyway, instead of moving the small weight on the right side of the scale to 3 TENTHS, I moved it up to the 3 marking. (45+3=48 - WAAYY overcharged!) I started filling cases and thought the case looked awfully full. I rechecked myself and found this error. My face and my M700 are very glad that I did! Not saying you made a mistake, but it is possible. Let us know what you find out with this mystery.
Selmer

Lots of things can change the deal pronto...Maybe your necks are too long and have not been trimmed; maybe your brass is thicker and the make of brass also can change the scenario, how long is the throat, and on and on. Also from your post I suspect you have loaded your brass too many times and its suffereing fatigue because you have apparantly fired it at over 3700 FPS and it won't last long at that.

The bottom line is your loads are definately too hot for your gun, cut back on the powder at least two grains.

As to trajectory and killing power differences you are at a point of deminishing returns past about 3200 FPS or even less..That extra 300 FPS really gains you very little in the real world of hunting.

Thanks for the input. Lots to considder.



Yes we did open the book and pick the load; except it was thestarting load!

The load had been worked up a few weeks ago. He used to shoot 67.5 grains and get 3,284 feet per second all the time. Since the rifle returned from the 'smith, we started backing the load down. First by seating the bullet away from the rifling .050" like Barnes suggests. Before he had it about .010" off the rifleing.

since the rifle returned from the smith

Now I have to ask what the smith was doing to the rifle

65grs of 7828 shouldn't be even close to a warm load....pull and check wieghts on everything as the others stated.

Brett

i would recommend a 30-06

I'll go get the popcorn!!!!

i know he is laughing. he helped me work up my loads for my 30-06. we went to the range together, and he put me on a chrono for the first time. he knows i will support his hyper speed quest. i however will continue plodding along at 3000 fps.

Ringman:Barrels.....I'll bet it's the barrels....I've got two 7 Rem Mag's downstairs that show over 200 fps difference with the same ammo,same day,etc.They are as different in what they'll digest as if they were different calibers. I have seen this a lot with 7 mags.

What kind of 7 mag and what barrel?