Thread: 7mm rem mag reloading issues

Hi guys, wishing everyone a merry festive season!
I’m new to reloading and am having some issues developing a load for my 7mm rem mag, hells canyon speed, 1 in 8 twist, 26” barrel. I tried 175 grain eld x with Reloder 22 and couldn’t find accuracy with different powder charges or seating depths. I switched to 168 Berger’s and h1000. Worked up to book max without finding pressure signs, settled for a mild charge producing 2950 fps, .3 grains above and below were showing very similar velocity, assumed a powder node. Tested seating depths of 10 thou jump, 25 thou, 50 and 70 thou. The promising looking depths after tweaking 2 thou deeper and shallower seemed to get worse. I have a common theme of 2 shots touching and one off an inch away. 4 shot groups give me shot 1 and 2 touching, and then 3 and 4 touching but an inch away. Leaving a couple mins between all shots. Same charge and depth tested 2 days apart revealed the same thing but the poi over the exact same target was off by an inch. I’ve had the bases and rings checked, the bedding checked and nothing was untoward. I feel very confident I have been pulling shots or flinching either. I’m using a gunwerks muzzle brake. Brand new Norma brass. Being as pedantic as I can with my powder weighing and seating depth, double checking everything. Factory ammo groups consistently. Is there maybe something I am missing? Any help or a direction to check in would be greatly appreciated
Cheers

What kind of stock? What kind of action? How was the bedding checked? Sounds like a bedding issue.

How long did you wait between shots?

The factory stock, comes factory bedded. Am experienced shooter, if that means anything, checked the bases and rings for torque aswell as the action screws, everything was as close to as it should be, he looked at the bedding and the only thing he could say about it was that perhaps the bottom of the recoil lug could be touching the bottom of the bedding.. apart from that the bedding looked normal he said. It’s a browning xbolt hells canyon

2 mins atleast, the barrel was only ever like warm. I wondered if it had a low tolerance to heat so I went back 2 days later and the poi on the same target had changed altogether

The top 4 on the vertical line were shot on Sunday, the other 3 lower and right were Tuesday

It’s double grouping - something is up with the action/bedding or mag box binding causing the action to not return to battery every time.
Firstly check that the action screws are torqued correctly. Then check that the mag box is not trapped and is able to move. If the mag box is trapped then you’re effectively torquing the action onto mag box rather than bedding pillars or bedding surface. If the mag box is binding then file a whisker off it so it’s free to move (slightly). If it’s not the mag box then there’s something up in bedding or recoil lug. Take the action out and examine it very thoroughly. If it’s binding or riding there will be rub marks, and then look at the stock bedding to see if there are rub marks in corresponding area. If it’s riding on recoil lug you can confirm this by using a blue or red marking pen to colour the bottom edge of recoil lug. Fit the action, torque it up then pull apart and see if the colour has transferred to the bedding.

Hold the rifle vertical and place the fingers of one hand on either side of the barrel at the end of the foreend so that the fingers are also just touching the foreend. A light grip is important. Then with the other hand undo the front action screw. You shouldn’t feel the barrel move, if you feel the barrel move the bedding needs redoing.
The other could be you need to jam the projectiles into the lands. I use to shoot 168 vld Berger’s in my 7mm mag and I jammed them about 15 thou into the lands. I used about 72.5gr 2217 and federal magnum primers.

I will give it a go, I’m away for a week unfortunately but as soon as I get back I will give each suggestion a try. Could it have anything to do with brass prep? As in shoulder “bump” and/or case neck length?

Greetings,
To me the problem is the two minutes between shots. It is almost impossible to sit rock still for two minutes again and again. Get into a comfortable shooting position and fire your group without waiting between shots and then inspect your group. Make sure that everything is the same in your hold. A better aiming mark could help as well. A hollow circle or square can help aiming precision. There may be nothing wrong with your rifle or loads.
Regards Grandpamac.

Hi mate, I had wondered about the getting up off the rifle between shots. I do spend the time assessing natural point of aim etc when I’m getting ready to shoot again. I’ve never before had a problem with getting the poa to match up with the poi on different days, obviously some days I shoot better than others but the poi was always in the same ball park. I will try like you say some shots in succession with as little coming off the rifle as possible and see how that goes
Thank you

Its a lot harder to consistently shoot light rifles accurately than people think, especially ones with fast twist & heavy projectiles

I would have to assume that a longer barrel would also allow an extra millisecond of time for a movement of some sort to affect bullet flight? Ie fundamentals and follow becoming even more important.. weird that the 1st 2 shots keep touching and then they chang poi consistently, across differing powder weights.. I would assume a shitty group not splits if it were 100% down to fundamentals and not be so repeatable. Could brass prep in way shape or form contribute?

I'd try 162s with same powder charge, I had a rifle that was presenting as double grouping with one projectile but fine with another, was a frustrating process looking for mechanical causes, grouping well one sessions then not the next etc, similar to the experience you are having, change in projectile had nice tight and consistent groups

The other thing to consider would be parallax

Are you running a muzzle break? I had a similar problem with my 300 WM, after much grief, mate picked up Break wasn’t quite square after 3rd shot. just wasn’t tight enough. Simple fix fortunately