Thread: 7mm RM rechambering

Check your mag length for the cartridges you are interested in for a rebarrel. Also, will the cartridges load and feed from your mag? And have you got a spare minimum of $800 for the rebarrel job (not counting the brass, dies, bullets, powder, etc)?

30/06 and be done with it.

Talk to Kiwi Greg. As above 180 eld or berger 180. 7mag 2900-3000ish give or take. Your barrel twist is boarder line and will show at distance more than close. Just because it's stable at 1000 doesn't mean it will be at a mile. 30 or 338 cal would be better. Comparing figures of energy etc isn't comparing apples with apples. 7mm doing over a 100fps faster and 45gn lighter bullet doesn't mark a steel plate that I use. A 30cal cal going slower with the heavier bullet both of the same construction puts holes in it. On paper nothing between them. In real world there certainly is. Like comparing a v8-v6 4cyl with the same hp and similar toque . Put a hill in front of them and see who runs out of puff first

Originally Posted by rupert

Check your mag length for the cartridges you are interested in for a rebarrel. Also, will the cartridges load and feed from your mag? And have you got a spare minimum of $800 for the rebarrel job (not counting the brass, dies, bullets, powder, etc)?

When I get into it I’ll fit the atlasworxs bottom metal using aics mags which will allow 3.6” COAL. That should allow a decent length projectile seating (although I don’t have any info as yet) and the actual case lengths are very similar to the RM, so should be ok there. And I found a thread of kiwi Greg that indicates the 7-375R would be suitable. And as for the cost, I assume a rechamber would be cheaper than a rebarrel, and I could utilise some projectiles and at least reuse the seating die.

Thanks for that info, working up a suitable 180gr load is where I’ll start, and just hand feed when shooting at distance. At the end of the day if I’m not capable of making those shots, then it would be a waste of money to step up to a larger cartridge

Originally Posted by r87mm

Talk to Kiwi Greg. As above 180 eld or berger 180. 7mag 2900-3000ish give or take. Your barrel twist is boarder line and will show at distance more than close. Just because it's stable at 1000 doesn't mean it will be at a mile. 30 or 338 cal would be better. Comparing figures of energy etc isn't comparing apples with apples. 7mm doing over a 100fps faster and 45gn lighter bullet doesn't mark a steel plate that I use. A 30cal cal going slower with the heavier bullet both of the same construction puts holes in it. On paper nothing between them. In real world there certainly is. Like comparing a v8-v6 4cyl with the same hp and similar toque . Put a hill in front of them and see who runs out of puff first

I’ve been halfway through a .338 edge build for the past 6 years or so. I’ve used a Winchester P14 action, but to complete that build, I need to spend a bit on a decent barrel and stock... and grow some nuts to see if the action will take it. So for now I’m just looking at 7mm cal which I really like.

Muzza's quick suntan make you a bit wary on the p14?

My opinion from doing the research, 7 Saum 1-8” 24-26” and 180gr eldm or similar with ADG or similar brass to give 3k a nudge...

Originally Posted by stevodog

Muzza's quick suntan make you a bit wary on the p14?

Haven’t found that thread, but even the thought makes my nuts shrivel a little bit...

"Cleanly take animals out to 1000m"



I'd urge against that unless you're really sure in your own and you your rifle's abilities. The chances of maiming/wounding an aminal goes up and up, as your ability to guarantee perfect shot placement goes down and down. 1000m is getting really sketchy and better balistics can only reduce the margin of error by so much. There's just so many variables, some of which you cannot account for.

Originally Posted by DBL

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

Impressive data, thank you very much for that, and will definitely look into 7-300 NM too. I hadn’t planned on opening the bolt face, but that is definitely an easy option, especially seeing the info you’ve just given

Originally Posted by Grimus

Impressive data, thank you very much for that, and will definitely look into 7-300 NM too. I hadn’t planned on opening the bolt face, but that is definitely an easy option, especially seeing the info you’ve just given

I dont believe 300NM class cartridges will fit in Tikka action. The cartridge is closer in size to .338lapua. It certainly wont fit in a Tikka magazine.

7mm with the right projectile will generally have better ballistics than the .300s. The only mainstream .308dia projectiles im aware of that has a higher BC than the 7mm 180 ELDM are the Hornandy 230 and 250gr A-tip projectiles, which only just edge out the basic (and cheap) 180ELDM. Hornady have not yet published the BCs for the new 7mm A-tips, but I have no doubt they will easily top the best BC 30cal projectiles commonly available.

The other thing to keep in mind is the twist rate of the standard barrel. It may not be sufficient for the heavy 7mm's.
The added velocity will offset some of the lack of twist rate, but will it be enough? Im not sure...would be borderline id think. (if we are talking 180ELDM)

Originally Posted by ChrisW

I dont believe 300NM class cartridges will fit in Tikka action. The cartridge is closer in size to .338lapua. It certainly wont fit in a Tikka magazine.

7mm with the right projectile will generally have better ballistics than the .300s. The only mainstream .308dia projectiles im aware of that has a higher BC than the 7mm 180 ELDM are the Hornandy 230 and 250gr A-tip projectiles, which only just edge out the basic (and cheap) 180ELDM. Hornady have not yet published the BCs for the new 7mm A-tips, but I have no doubt they will easily top the best BC 30cal projectiles commonly available.

The other thing to keep in mind is the twist rate of the standard barrel. It may not be sufficient for the heavy 7mm's.
The added velocity will offset some of the lack of twist rate, but will it be enough? Im not sure...would be borderline id think. (if we are talking 180ELDM)

@ChrisW Thanks for that authoritative advice. Norma state the 338NM and 300NM were designed to swap out in actions made for 338LM.

Do you think the 300NM would work well enough in the Sako 85 long range XL action or the TRG M10 ? Come to think of it. Are those in the pipeline as factory options ?

Originally Posted by Bagheera

@ChrisW Thanks for that authoritative advice. Norma state the 338NM and 300NM were designed to swap out in actions made for 338LM.

Do you think the 300NM would work well enough in the Sako 85 long range XL action or the TRG M10 ? Come to think of it. Are those in the pipeline as factory options ?

Yep, all those will easily fit in the Sako Long range XL action or the M10. Im not aware of any of the Norma Magnums coming as factory offerings but I do know 6.5PRC is in the works.

Originally Posted by 25 /08 IMP

Arthur Cleland will I think

Sent from my CPH1903 using Tapatalk

Originally Posted by Stocky

Let us know how that gets on with Greg.

Originally Posted by Spitfire

Dave Ward in Dovedale does. He’s doing one for me as we speak - 7-08 to .284 Win. The last one he did shoots 162s ELD-X into .5 MOA 5 shot groups. He knows what he’s doing.

Bit of an update, Dave Ward does, but doesn’t have the 7BM reamer. And Arthur Clealand does, and has quoted me $350 to rechamber, including a bit extra to get the reamer... bargain if you ask me