6.5 150gr SMK twist rate

[FrancoisBuys]

Good day reloaders

Ive been looking into the 150gr sierra MK on my 6.5 PRC. Sierra says a 1:7.5 twist rate is requiered. Im running 1:8 twist. After doing some homework I found that Hornady and Berger says a 1:8 will shoot the 153gr A-tip and 156gr EOL just fine, the EOL is also longer than the SMK and the A-tip is the same lenght as the SMK. My rifle runs 147 eldm very sweetly going under .5moa at 2950fps

I dont understand how the other 150gr+ bullets will shoot fine out of a 1:8 twist but according to sierra the SMK wouldnt. Anybody who tried the 150 SMK out of a 1:8 tube? And is the gain in BC from the 147 eldm to the 150 smk worth the trouble. Its a step up from .697 to .713.

 

[Jerry M]

Personally I would follow the bullet company's recommendation. Okay accuracy and exceptional accuracy and two different things. Bullet weight, ojive, length all play a role.

Good Luck

 

[Laphroaig]

Velocity plays a part too, and 6.5 PRC has a couple hundred fps over say, the Creed. It's so close that the only way to tell for sure is to give them a try.

That's a pretty slim increase in BC and if the 147's shoot for you don't lose much if the 150's don't stabilize.

 

[redcon1]

Good day reloaders

Ive been looking into the 150gr sierra MK on my 6.5 PRC. Sierra says a 1:7.5 twist rate is requiered. Im running 1:8 twist. After doing some homework I found that Hornady and Berger says a 1:8 will shoot the 153gr A-tip and 156gr EOL just fine, the EOL is also longer than the SMK and the A-tip is the same lenght as the SMK. My rifle runs 147 eldm very sweetly going under .5moa at 2950fps

I dont understand how the other 150gr+ bullets will shoot fine out of a 1:8 twist but according to sierra the SMK wouldnt. Anybody who tried the 150 SMK out of a 1:8 tube? And is the gain in BC from the 147 eldm to the 150 smk worth the trouble. Its a step up from .697 to .713.

Why not just shoot it and see how it does?

 

[FrancoisBuys]

@Laphroaig Ive read an article where a guys shot them fairly decent out of a 6.5creed with a 1:8twist. Guess the only real way to see if they will stabilze is like @redcon1 said, shoot them and see. It looks like a bullet that will just fly forever aspecially at PRC velocities. A friend of mine is running a 22-250 AI with a 1:8 twist. He shoots 95gr SMKs with no issues even though sierra says the a 1:8 is to slow for that bullet

 

[Frm57]

Elevation matters also…. Various on line calculators you can use.

 

[troy fairweather]

Guys are shooting the 156s with 1-8s so I'd think you would be good.

 

[FrancoisBuys]

Guys are shooting the 156s with 1-8s so I'd think you would be good.

Thats my thinking aswell. But I actually decided to skip the 150 smks for now. Its not woth burning valuable powder and primers that are very hard to find just for a .1 gain in BC over the ELDm

 

[troy fairweather]

Thats my thinking aswell. But I actually decided to skip the 150 smks for now. Its not woth burning valuable powder and primers that are very hard to find just for a .1 gain in BC over the ELDm

Ya eld m shoot good in mine, can get them up to 3000 with the 24" tube maybe more since the barrels sped up . Some guys I've read pushing the 156 hitting 3000 with 24" barrels . Mine is more a deer rifle so no need to stretch it's legs out much. Cheap 140 Speer hot cors are shooting 1/4-1/2 moa if you need a cheap deer bullet.

 

[243winxb]

Temperature & Altitude makes a difference what works or doesn't. If you believe in calculators? https://bergerbullets.com/twist-rate-calculator/

Bullet lengths- https://www.jbmballistics.com/ballistics/lengths/lengths.shtml

I shot some 140 gr match burners bullets in 6.5 Creedmoor, using a reduce loaded of IMR 4198. Accuracy was same or better then full velocity loads at 100 yards.

Don't know till you try.

 

[FrancoisBuys]

Ya eld m shoot good in mine, can get them up to 3000 with the 24" tube maybe more since the barrels sped up . Some guys I've read pushing the 156 hitting 3000 with 24" barrels . Mine is more a deer rifle so no need to stretch it's legs out much. Cheap 140 Speer hot cors are shooting 1/4-1/2 moa if you need a cheap deer bullet.

Last time I checked the velocity on the 147 eldms they where running at 2950fps. But at that stage the barrel only had 30 rounds through it. It might have crept up close to or over 3000. The 142 SMKs was running at 2970 at the same stage. I use it as a long range targer rifle. Taking it out to 1.2km(think thats like 1300yards) next week, so a bullet with a high BC really helps alot

 

[FrancoisBuys]

Temperature & Altitude makes a difference what works or doesn't. If you believe in calculators? https://bergerbullets.com/twist-rate-calculator/

Bullet lengths- https://www.jbmballistics.com/ballistics/lengths/lengths.shtml

I shot some 140 gr match burners bullets in 6.5 Creedmoor, using a reduce loaded of IMR 4198. Accuracy was same or better then full velocity loads at 100 yards.

Don't know till you try.

Ive actually used both these sources to try and fined an answer. But sierra says the "uncoventional .27 ogive", ive no idea what is ment by that, needs a faster twist... Berger's calculator does say the bullet is flying stable.