Thread: 7mm RM rechambering

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