7mm 10-twist for 7-RM ?

[7mmShooter]

If you're putting a new barrel on it go 9 twist. As has been said, 9 will run the 140s just fine, and be much easier to sell if ever needed.

 

[BallisticsGuy]

140's are nothing to worry about as far as stabilization. What they do to meat is another thing entirely. There's quite a few deer I shot with a 7RM and a lot of those were 140's. Inside 100yrds they're just ridiculously devastating meat destroyers. Shoot it in the neck if you can. 3200fps is nothing to sneeze at. My 10 twist 7rm isn't limiting me however if the barrel maker I used had offered a 9 twist I'd have taken it. I already had a 9 twist 7mag gun specifically for 180's. My 10 twist I built specifically for 168 grain Bergers and 154gn Hornady's (EDIT: would be nice if it'd do 180's at full stabilization though). So, does it make sense. Well my having done it isn't a selling point on that front but it does mean you're not the only one out there and so that alone could serve as justification for you. Do what you want. Only you can judge you.

 

[Norseman]

120 grain Nosler Ballistic Tip is ideal and flat shooting. Jacket are thicker than the 140 and 150's, tough bullet indeed!!!!!!!!!!!!!