7mm 10-twist for 7-RM ?

[hemiford]

I have a spare magnum 700 long action (!) and thinking of ordering
a 10-tw barrel to shoot only 140-gr projectiles, chambered in 7-RM.
I generally shoot heavier bullets from my current 9-tw 7-RM.

I can shoot 140's from my 9-tw barrel too, just wondering what
I might really gain from the "special" barrel. Am seriously considering
making it a 30" barrel to boot.

 

[PackersFanboy]

ballisticstudies.com /140 grain bullets, driven at velocities of between 3200 and 3300fps, the 7mm RM delivers extreme trauma on light bodied game out to ranges exceeding 400 yards. This bullet weight tends to lose its ability to produce wide wounding at ranges of around 650 yards. On heavily built medium game, the 140 grain bullet can produce somewhat less than ideal performance, wounding and penetration may be adequate but results can be erratic./ driving faster make it worse

 

[Frank in the Laurels]

If your going to shoot only 140's the 1 in 10 will be fine, if your plan on shooting those super long missiles like the 180 bergers and I'm not sure someone may make bigger these days go with the faster twist...

 

[TOM H]

Years ago I purchased 7 Wby mag and it had 1/10 twist barrel and I think still make it with that twist. Hodgdon/Hornady loading data for 7Wby they used 1/10 twist barrels.


I think you been fine with 1/10 and that 7 Wby I shot 154gr Hornady for elk/deer here Co.

 

[7mmShooter]

If your going to shoot only 140's the 1 in 10 will be fine, if your plan on shooting those super long missiles like the 180 bergers and I'm not sure someone may make bigger these days go with the faster twist...

Oh there's a lot bigger, how's a 226gr Chinchaga sound? gun)

 

[BallisticsGuy]

I use a 10 twist in 7RM for up to 168's with good results. I've pushed some 180's out of it too and they seemed stable enough but that was a lark and not intended to be done again. The 180's I don't have trouble getting 2900fps from which is pretty spanky with a .67x G1 BC.

 

[Varmint Hunter]

I see no realistic advantage to a 10" twist. It may shoot slightly faster or foul slightly less but that's only a guess. On the other hand it would limit bullet selection when the current trend seems to be towards heavy for caliber, high BC bullets.

I'd opt for a 9" twist which will shoot the 140s just fine and leave you with the ability to use some of the newer heavies if you have a change of heart.

 

[Frank in the Laurels]

Hey shooter, I'd like to see a pic of one of those, must be 2 inches long!!!! What the BC, 2000!! Lol

 

[7mmShooter]

Hey shooter, I'd like to see a pic of one of those, must be 2 inches long!!!! What the BC, 2000!! Lol

No clue on BC (being tested by Bryan), but the 226gr 7 is left center, 300gr 338 right center. Second pic is the 300gr Chinchaga next to Berger's 300gr Hybrid

 

[BallisticsGuy]

Holy bearing surface length batman!

 

[Predator 22]

^^^ What he said.

 

[Jordan Smith]

8 twist and don't look back...

 

[hemiford]

OK, OK, back on track please.

140-gr bullets in 7-RM, 10-tw.

Not 226-gr bullets, not 8-tw.

Thank you.

 

[Predator 22]

I have a 7mmx61 Schultz & larson that has a 12 twist barrel. It will shoot up 150-154 grain flat bottom bullets tops. It's a neat case but the 12 twist basically just cut it off at the knees. It hasn't even been out of the safe for more than its annual lube job for about 6 or 7 years. So in all seriousness I wouldn't build a 7mm on anything less than a 9 twist. You can still shoot 140 grain and if it doesn't like them you can go up a little in weight and if you have to sell it in the future it will be a lot easier to sell with a 9 twist at least to someone who knows the difference.