which 7mm

[Long Time Long Ranger]

The 7 super mashburn has held some popularity for many years. It beats the 7mm remington and is still short enough to allow long bullets to be seated and feed through the magazine. Like AZ said similar to the 7mm-300 winchester that has hung around since the 60's.

The 7mm Ackley mag is basically the same as the STW. About all you can get from a blown out H&H mag case. I like the STW there because it is factory and I need more performance difference to go wildcat.

All are fun just depends on if you want something not many have or something you can easily find components for.

 

[Jordan Smith]

The RUM will give you the best chance of getting that 195gr bullet to 3100fps.

 

[Skimbleshanks]

Did some rough maths tonight. The RUM with the 180 Berger seated to the neck shoulder junction was a hair over 4" long. way too long to feed from a magazine even with the wyatts box. a 7-338 norma was hovering a hair over 3.6" long. I dont have exact measurements on a 7-338 norma but it looks promising and with a case capacity rivaling that of the RUM, able to feed from a magazine(length wise at least) and good brass I am seriously considering the Norma. I really want this to be a repeater. On top of that I would much rather have a middle of the road load in a bigger case to get the velocity than a max load out of a smaller case. Like a 500 horsepower 454 or a 500 horsepower 350. One will be way easier to achieve.

 

[Long Time Long Ranger]

Some guys will open up a remington bolt face to fit the Norma and some will not because of liability. You might want to check on what people think about that. I think you would be better staying with a cartridge your action was designed for.

 

[Lefty7mmstw]

Go with the stw.I've had one in the stable for over 10 years and it's been very good to me. I've had the 7rum and currently own a 30rum, but the 7stw is in many ways better than both of the others. You can make brass from either of the holland cartridges, the 8mmrem, or the la weatherby rounds, so contrary to popular belief, good brass will always be around.
It has better case capacity than the 7-300 or mashburn, has a lot of good data for reloading, dies are common(not hundreds for the set), and it will go 2000 rounds on a good barrel if you don't beat it up(the 7rum will die before 1000 if you don't down-load it). There are other reasons too, like the fact that it is the smallest cartridge that will deliver 2000 foot pounds to 400 yards with full house hunting weight bullet rounds. The fact that you can shoot one prone without a brake on it; try that with a 8.5# 300u-- you'll be getting stitches and the 7rum would be close.

 

[Lefty7mmstw]

You have a 30" barrel for the build. I'm assuming it will be finished in the 28-30" range. You will easily be able to take the 180 to 3100 fps + and the 195 will be in there too, maybe 100 fps slower.
I've got an stw with a 24" barrel( around 9#scoped), and she'll do 3100 fps on a 171 barnes with rl25, and I haven't looked at magnum or retumbo. It shoots better at 2950 fps, and will put 3 into .3" at 100 yards at that speed. I shot the 171 with rl50 once, and it was 3100 fps with good accuracy, but some lout shot my target on me so I have to re-shoot it to make sure. For now I've loaded 100 rounds of the 171's with rl25.