7mm Mag Rechamber

[dogz]

The 7mm Mashburn Super Magnum leaps to mind!

Bingo...............give that man a cigar

I've been using one for 3 decades, it's been kicking around since the 60's

 

[baldhunter]

I have a couple of 7STW's.It's a great cartridge.Mag box length limits this cartridge.Make sure to check the mag box of your rifle before choosing what cartridge you decide on.Brass availability is another thing to think about.Sometimes 7STW brass can be hard to find.I'd think about doing a 7-300 Win Mag.Win Mag brass would be easier to find.It would give you a little extra mag box room over the 7STW.The case capacity is just a little less in the Win Mag case,but in reality,you have to get into the really slow powders to fill the STW case.So really the difference between the two depends on what powder your using.I think you would find them closer to equal than not.

 

[jsmitt6]

Here's a picture of the shank, it seems pretty small to me, compared to what my PBB or Xcalibers have.

I have a buddy who has chambered and made a few prefits in the past for me. After talking with him this morning, he doesn't want to have to deal with cutting off the tenon threads and trying to pick it back up.

I may just keep the 7RM as is, i was just curious on what my possibilities would be to clean up the chamber into a different cartridge. Thanks all for the responses!

 

[jsmitt6]

Agree
Need to know more about the bbl. The amount you cut off matters for sure. You need to measure your shank length. Then consult with your smith on what your options are

If you are dealing with a stock Rem shank length of around 2 inches and a standard sporter barrel, going to be tough to get to the Medium and small calibers - probably have to stay in the LA magnums and even then, you may be close

It's a proof carbon barrel. The shank looks smaller than my other barrels, I'm not sure who the smith was for this barrel.

 

[jsmitt6]

A 7/300WM would be cool.

Essentially a 300 win mag necked down to 7mm?

 

[jsmitt6]

First thing I'd do is check the throat or measure where the good rifling begins. Now, what is the target animal 90% of the time and the bullet of choice? Then I would shop for my favorite brass brand and buy a bunch.

No target animal in mind. Never bigger than Elk. Admittedly I don't know much on this bbl. Just got it in a trade.

 

[jsmitt6]

You possibly won't need to cut any part of the tenon if you chamber something in a slightly larger in diameter and length case. Headspace on a shoulder fit might be needed (not my area of knowledge), but the action would needed for measurement to headspace properly. If there's enough length to have for re-tenon then going saum, wsm or prc is possible. If not, going 28n, rum or stw is the way to go. Would you be using a different stock or be limited to 3.340ish length?

No limitations right now. Using an origin action, haven't picked out a stock. Just currently mulling over my options!

 

[jsmitt6]

Sounds like you will be doing your own work? If so it is not terribly difficult and very cost effective especially if you rent a reamer.

If you are having a gunsmith do the work, then the least expensive process is to ream the chamber to a larger size.

For any setback work (cutting off some of the shank) if the existing barrel shank is shortened then the shoulder must be moved forward and the thread continued to properly fit the same action. Picking up the existing thread and continuing is a PITA but can be done. Would be easier to remove the entire shank and start over but that would move the barrel rearwards in the stock most likely making a larger gap in barrel channel.

Easiest way is to pick a larger chamber reamer that will clean up the existing 7 Rem mag chamber. Other posters have mentioned some. Having a lathe and a bunch of reamers I have done this with a 243 going to 6mm-284, 7-08 to 284 Win, 25-06 to 257 Weatherby and 300 Win mag to 300 Rum to name a few. It is the simplest approach.

I took a Rem takeoff in 7 Rem mag cut off some of the shank, turned down shank and rethreaded for a Ruger and make it a 284 Win. Same sort of thing with a Rem takeoff to fit a push feed model 70. Both of these actions use a 1" diameter x 16 TPI so a Rem shank with its larger 1 1/16 dia x 16 TPI can be turned down and threaded.

Tikka T3 barrel is also a 1" x 16 tpi but its shank is longer than a Ruger or Model 70 push feed so some has to be removed and then rechamber.

This was insightful, thanks for your response!

 

[Elkmann]

Essentially a 300 win mag necked down to 7mm?

Yes sir

 

[Ark. Trapper]

No limitations right now. Using an origin action, haven't picked out a stock. Just currently mulling over my options!

The origin action is 1.060"x20tpi. The 7-300, 7STW or the 28 Nosler would all work without having to re-cut threads. See my post from above. The only issue you may have is if the tenon on that barrel is currently cut for M700 threads at 1.062"x16tpi then you won't be able to use it without either cutting the tenon off or turning it down and building a bushing.

 

[dogz]

Bingo...............give that man a cigar

I've been using one for 3 decades, it's been kicking around since the 60's

 

[southpa]

If it's a saami chamber you could just run a throater down her and give it a lil more free bore and play with some 195s
73ish grains of retumbo could play nicely with some 195s

 

[jsmitt6]

If it's a saami chamber you could just run a throater down her and give it a lil more free bore and play with some 195s
73ish grains of retumbo could play nicely with some 195s

This is interesting..Great idea!

 

[southpa]

This is interesting..Great idea!

Ya throat it long and play with some 190atips or some 195 bergs would be my choice.