Thread: A bit of 7mm advice

About a year ago I got the idea I needed a tops style rifle and have finally got the bones of it together. T3 with 22" barrel, T2 brake, Leupold VX5-HD 3-15 and a B&C stock awaiting a Stug job. Going in for my first Tahr soon and now that I have some loads shooting well will be getting back in to the Kaimanawa tops. Current calibre is 7mm Rem Mag with a 1:9.5 twist. I find the 162gr ELD-X shooting well but am limited on seating depth due to mag restriction. Moving forward I see a rechamber or new barrel and cartridge. Ideally I would like to be able to shoot bullet weights from 160-180gr and have the freedom to seat them wherever I want. In my mind the logical idea would be a rebarrel to a 7WSM. Unfortunately brass is pretty hard to come by (as well as the 7SAUM) so then the 7-300WSM starts to look better but pretty mixed reviews as to the work required to size the brass and then ensure that the chamber is set up correctly.

Anyone have much experience with the 7-300 or any of the other short mags in 7mm that would be a suitable switch? Likely go 1:8.5 twist for a bit more stability. Love the T2 brake so that will be retained. I haven't shot many of the heavier bullets as I'm restricted by mag length so can't really play with seating depth and have been informed that 1:9.5 is only good to 160ish.

Not sure what the 7wsm or saum will do that your remmag wont mate even at mag length. Maybe try some other powders and see if you can wring more juice out if that's what you are after.

To get the real advantage out of the 180ish grains you need bigger than a 7mm mag. The 160gr projectiles are the sweet spot for the 7mm mag capacity calibres. What is the issue with seating to mag length? Do you not have the accuracy or velocity you are after?
The WSM/SAUM case diameter cartridges are not ideal in a T3 due to action/barrel diameter. I remember Greg Duley writing something about it. Something about barrel thread diameter being too small and getting too much expansion.

My t3 shooting the 162 at mag length gets awesum speeds you might need to try a new powder of your after more speed. Seating depth is only an issue if it wont shoot.
Other option is to run a mag length round have some some single feeders for the longer shots but thats a lot of mucking around

7mm Blaser Magnum fits perfect in Tikka T3 magazine with projectiles seated right out

Cheers fellas. There's not really any issue with what I have but it's a bit boring. The short mags seem a bit more powder friendly. Also, not sure if mine has a slightly longer throat or something like that but I'm 0.040" off of the lands at mag length with the ELD-X. In reality it's likely more me just wanting something that I can have a bit more of a play with if I'm going to go down the road of rebarreling one day. If practicality was the only consideration life would be a bit boring.

Latest issue of NZ Hunter has a good article on the 7mm "super pig" chamberings. Pros and cons of the different 7mm magnum cartridges for a shorter barrelled rifle. They do say that the T3 7mmRM has a long throat.
Also yo say you have a 22" barrel. Shortened from standard obviously.

Originally Posted by Echo

7mm Blaser Magnum fits perfect in Tikka T3 magazine with projectiles seated right out

This is looking pretty interesting. Wasn't even on my radar. Do you have a good info source for details?

I had a t3 7mmRM, T2 break, standard stock and a 3-15 Zeiss so pretty much identical. I loaded the 162 Amax's to fit mag length, 72grs of 2217 and it shot 1/4 groups on a bad day, honestly (3000fps iirc) that's more then enough gun unless you want to step up to a 28 Nosler or something, but if I wanted to go bigger I would probably go 30cal.
I would just go with the new version. Of the 162's and load them up and give it a whirl.

I built a 7-300 and brass is easy to size. Went with std shoulder, just a straight neck down. I love it.

Originally Posted by Chicken

I built a 7-300 and brass is easy to size. Went with std shoulder, just a straight neck down. I love it.

Who has the reamer? Who chambered it?

Originally Posted by Chicken

I built a 7-300 and brass is easy to size. Went with std shoulder, just a straight neck down. I love it.

7-300 What?

Originally Posted by camo wsm

7-300 What?

I'm assuming its a 7mm/300 win mag

Nathan Foster has put a bit of work into it importing Lee dies and has a reamer

His model has an improved shoulder which needs fire forming

He also left the neck long with his chamber reamer to allow for case growth....but reduced the chance of that with the improved shoulder angle...never could understand that

Its about the perfect maximum case capacity for a 7mm bordering going overbore

Could be 7/300 WSM ?

good point

You can load them with a longer oal just single feed them which isn't a problem if you are hunting LR.

Also could go to ar2225 which should fling them along a bit faster than 2217.

Your barrel should stablise 180's ok I would have thought.