7mm mag… try to push heavies or not?

[ZacSquatch]

Have a new Sako S20 in 7mag and been getting brass fireformed for it with factory and stuff I loaded for my old L61R. The twist is an antiquated 1:9.5 and I wish they had kicked it up a notch.

I have a few boxes of 175 ELD-X and SMK’s but should I even bother trying to work a load on them? Both suggest a 1:8.5 and I may just sell them off if it’s going to be a waste of my time.

 

[Mag_7s]

I wouldn't try to develop a load for those bullets, pretty likely they won't stabilize properly. At the cost of components right now I would find a bullet that fits your intended purpose that will stabilize with that twist.

 

[5MilesBack]

I've loaded and shot a lot of 175gr Partitions in my 7mag with a 9.5 twist, but I'm pretty sure it's the length that's the problem with some of those others.

 

[mtnrunner260]

I could not achieve satisfactory results with 175 eldx in a 9.5 twist, 26in shorter barrel at 5000 ft using retumbo.
With more effort it may have been possible but I went back to 168 vlds.

 

[Pony Soldier]

I do fine with interlocks at 175 and have for 30 years. I experimented with eldx 175 and they were great at 50yds but when I stepped out to 100yds, they spread to 8 inches. I threw them out and went back to what worked. Be careful!

 

[Blinddog]

Most 7mm's like 160gr.-168gr. I have had the best results with 160gr. partitions. from 50-500 yards.

 

[LeftyWilbury]

I haven't found a reason to go heavier than 168 berger in my 7 mags. And now I hunt w 140-150 gr barnes. I feel like the whole point of burning all this powder in the 7 mag is for speed....and if the twist rate is marginal for the heavies, I'd save em...for the next 7 mag ya buy.

 

[MThuntr]

Drop down to the 150 or 162 ELD-X and let 'er rip

 

[KenLee]

We always spit 139 gr BTSP Hornadys out of our 7 mags with excellent results. Whack!!!

 

[Pharmseller]

160 Partitions, then they became scarce so we moved to 162 ELDX and haven’t looked back.




P

 

[35WhelenAI]

Haven't loaded for the 7mm Rem Mag in a while, however BC between the 162 ELDX and 175 ELDX isn't enough to sneeze at when looking at the 162 being pushed faster, IMO. Offer up the 175's for sale and don't look back using the 162's.

 

[CHWine]

160 accubonds have been my medicine for years now. Luckily I have a decent supply but hear they're hard to find now.

 

[menhaden_man]

Have a new Sako S20 in 7mag and been getting brass fireformed for it with factory and stuff I loaded for my old L61R. The twist is an antiquated 1:9.5 and I wish they had kicked it up a notch.

I have a few boxes of 175 ELD-X and SMK’s but should I even bother trying to work a load on them? Both suggest a 1:8.5 and I may just sell them off if it’s going to be a waste of my time.

Bullet Gyroscopic Stability Calculator

Calculate the Gyroscopic stability of a bullet with the Miller approximation.

bisonballistics.com

 

[menhaden_man]

Twist Rate Stability Calculator

Our newly updated Twist Rate Stability Calculator not only tells you what your SG is, but it also lets you know if you are reaching your optimized BC.

bergerbullets.com

 

[TxLite]

I have a 9.5 in my Bergara Ridge and am using retumbo to push the 168 Berger VLD 2975 with great accuracy. I haven’t tried to go any heavier

 

[EdP]

Secant ogive and polymer tip both add to the length of a bullet without increasing it's mass and therefore increase the twist rate needed to stabilize. You might try a tangent ogive bullet.

 

[Mag_7s]

To add to what EdP said with respect to secant ogive bullets. The relationship between the center of mass and center of pressure acting on the bullet are going to want to cause the bullet to not fly true. Think of it kinda like throwing a football, a tight spiral will fly better than slowly spun spiral. The further the two variables are apart the more difficult it is to stabilize, meaning you will need a faster twist to correct the imbalance.

 

[craveman85]

A friend of mine is currently loading that twist and his won't stabilize the long, heavy bullets. Most hit the paper at an angle at 100 yards.

 

[Balderdash]

I'd at least try. I ran 175's in OEM 700's at sea level without any trouble. IIRC, they were also 1:9.5.

 

[EdP]

A friend of mine is currently loading that twist and his won't stabilize the long, heavy bullets. Most hit the paper at an angle at 100 yards.

That is the expected result if the bullet is not stabilized. The destabilizing effect of bullet velocity is offset by the gyroscopic effect of rotational velocity (spin) when a bullet is stable. The velocity of a bullet in flight decreases faster than its rotational velocity so stability increases with time in flight, at least until the supersonic/subsonic transition is reached. Any problem stabilizing a bullet should show at 100 yds and if you are good at 100, it should stay good for all practical hunting ranges.