Thread: 7mm RM rechambering

OK, so this is a total pipe dream at this stage, but I’m looking at re-chambering my Tikka 7RM. I’m looking at 7-375 Ruger, or possibly 7-300 PRC.
The thought behind it is, I want to keep it mag feed-able, drop the belt, and increase range.

First question, can anyone recommend a decent smith for re-chambering? And also dies etc
Second question, has anyone got these calibres, and what are positives vs negatives of each.

Thanks in advance for any insights

The first question is what do you want to achive? If you want more range your better stepping up to a bigger .30cal. with 210eld's They suffer less in the wind and release more energy at range and yes I've got a 7mmRm. and shot it at range.

I’ll be completely honest here... there is a lot of the “cool” factor coming in here, but what I want is to increase the range to point where I could possibly hit steel out to 1 mile. And if I’m up to it, cleanly take animals out to 1000m

Hi Grimus,

This is a great idea and I hope you pursue the project and post pictures of your progress. Do have a chat with Kiwi Greg as he has a 7mm 300NM reamer that could make your life easier.

The previous statement that a .30 cal would do better in wind doesn't mathematically stack up when you compare a 300NM running a 230gr Berger Hybrid @ 2934 fps VS a 7mm 300NM running a 195gr Berger EOL @ 3150 fps. In a full value 12mph wind from 3 o'clock with a density altitude of 0ft (sea level) you will have the following holds (excluding aerodynamic jump, spin drift, etc):

300NM @ 2934fps
1000m: 7.60mils up / 1.85mils R
1500m: 15.50 mils up / 3.24mils R
2000m: 28.03 mils up / 4.96mils R

7mm 300NM @ 3150fps
1000m: 6.42mils up / 1.66 R
1500m: 13.08 mils up / 2.91mils R
2000m: 23.68 mils up / 4.56 mils R

MV's are close to actual. You can possibly ramp MV in both up but intent here was to compare apples with apples as much as possible. I'm not sure what barrel length you are running but have a chat to your gunsmith on what will work best for your 7mm wildcat.

Lastly, make sure you have good glass with the required elevation capacity and rail.

Cheers,

JT

Some good advice above.

T3s are great donors for custom or semi-custom builds, but not ideal for magnum cartridges. The action is not really strong enough, the magazine is too short, the barrels too thin and the recoil too stout. The max OAL you will be able to extract an unfired round is 3.5” in a T3.

As others say, the ELD-M 180 in your 7 RM would be the go, but you will need to forget mag feeding. Powders like RE26 and 33 will fix you up. If you want to go .30 cal you will need to be in the 230+ grain projectile range to match the 180s and recoil will be stiffer.

Do you have a reason for wanting a non-belted magnum? I keep reading about blokes who want this but they rarely seem to know why other than reading that belts are superfluous. A belt is not an issue at all and the case only headspaces off it on the first firing anyway.

It’s your choice and you should have what you want, but the T3 isn’t the best choice for your project.

BTW - I have a T3 based .300 Win Mag and it’s good, but not ideal.

.......... and talk to Kiwi Greg. He has a huge variety of 7mm ways to deplete your bank account.

Cool. Kiwi Greg has a write up on the 7-375

Without a complete re barrel

Originally Posted by stevodog

Cool. Kiwi Greg has a write up on the 7-375

thanks for that mate I’ll look it up

To be honest you will waste a ton of money and end up with a rifle that won't sell for anywere what it cost.(been there, done that) Sell the tikka and buy one in any of the new 30 cal magnums, Yes you can hit steel with 7mmrm at a mile if theres no wind, you might want to talk to the guy's who do the toby shoot, but any wind and it's just a guess on your part.

Not keen on selling up,

Tikka probably not the best platform for such a chamber/calibre. Your 7mm RM is quite capable for animals out to 1000 yrds so long as you run the right pills and you/rifle are up to it and you can judge wind well. That applies equally to 30 cals too imo !
How many rounds thru the current bbl ? Whats the twist rate ?
You could risk spend some serious $ getting it done and end up with a dog.
If you want to go to any of the "big 7's", you really need fast twist 26in bbl.

Still brand new, only had 10 rounds through. Just about to work up a load with 162gr eld-x’s and RL22, see how that goes for speed/accuracy. If it doesn’t like the elds, I’ll try nosler 168gr LR’s. It’s just a standard 1/9.5” barrel so definitely not fast twist.

Originally Posted by Grimus

Still brand new, only had 10 rounds through. Just about to work up a load with 162gr eld-x’s and RL22, see how that goes for speed/accuracy. If it doesn’t like the elds, I’ll try nosler 168gr LR’s. It’s just a standard 1/9.5” barrel so definitely not fast twist.

If i were you and wanting to extend the range/hitting power of what you have. Id forget about mag feeding it, and look at running the 180gr eldm seated out as long as your chamber will allow. Im running them in a 22" barrelled 284 win at just shy of 2800, the 7RM will push them lots faster with the right powder and will give you alot more energy down range and im picking a windage advantage over the 162/168 at higher velocity.

Im shooting the 180s out of a old factory tikka M595 9.5 or 9.25 twist or whatever they are and it shoots them extremerly well. So your standard barrel will likely shoot them well.

If you want to rechamber it, id look at the 7mm Blaser Mag cartridge, i believe it can be done on a T3 no problem. and will give a handy powder increase over the 7RM and no belted case if thats important to you.

Originally Posted by Grimus

Still brand new, only had 10 rounds through. Just about to work up a load with 162gr eld-x’s and RL22, see how that goes for speed/accuracy. If it doesn’t like the elds, I’ll try nosler 168gr LR’s. It’s just a standard 1/9.5” barrel so definitely not fast twist.

you can achieve more with your RM but need to go to slower burn rate powders like RL25 or 26, or AR2225, and like @GWH says bigger , higher BC pills like the 180 VLD's or ELDM's even if that means single feeding.
I believe the Duley's have even gone to RL33 in 7mmRM's with some success.