Range Report 150 grain 7mm SMK @1000 meters

[MacJannan]

Hello I have a quick question, In 7mm 08 does the sierra 150 grain match king stabilize out to 1000? Or am I better off with the 150 ballistic tips? I have a long range shoot on Saturday. My only rifle running right now is my 700 in 7mm 08. I usually only shoot out to about 500 yards with this rifle, but I am curious to the SMKs. Someone told me the 168 SMKs in 308 do not stabilize out to that range so I am curious if anyone has any feedback on the projectiles performance at that distance.

thanks for the help
Wow first post. so much info here.

 

[bohem]

Re: 150 grain 7mm SMK @1000 meters

If you can launch them at 2850fps or better then I'm getting them to be at 1300fps across the 1000yd line for 1000' DA's

I don't know where you're going to be shooting but this seems like a reasonable expectation of them getting there.

The 168 SMK's in 30c don't necessarily have anything in common with the 150's in 7. They may, they may not. I would have to look at a print, but there are a number of SMK's in 6.5, 7, and 30 that will transition and remain stable.

Hope that helps. If you can tell me what appx. altitude and temp you'll be shooting in, as well as your MV then it can be pushed through JBM to take a look at the speeds when it crosses 1000yd

 

[mwroseberry]

Re: 150 grain 7mm SMK @1000 meters

bohem - you forgot barrel twist. Makes a huge difference in stability at speeds. My brother has an 11.5 twist on his 7mm-08 and he can only run the 120s. Where my 1 in 8 twist I can push the 190s if I want.

Good luck,
Merritt

 

[bohem]

Re: 150 grain 7mm SMK @1000 meters

Yep, quite right. I was assuming that he had the twist to shoot the 150's since I expected him to already be shooting them at 500yd.

 

[mwroseberry]

Re: 150 grain 7mm SMK @1000 meters

Correct but having the twist at one range may effect his stability factor at another. If he's shooting a 1 in 9 at 2775-2900 he should be fine at 1000.

Good luck,
Merritt

 

[MacJannan]

Re: 150 grain 7mm SMK @1000 meters

Rifle twist is 1-9.24 inch barrel MV is 3000 fps 50.4 grains Vihtavuori n160 powder, 1/2 moa load. Not may daily load just for this event. Hard on brass other then that no huge signs of pressure. elevation is I think around 4000 feet and temp is 68 degrees.

 

[bohem]

Re: 150 grain 7mm SMK @1000 meters

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mwroseberry</div><div class="ubbcode-body">Correct but having the twist at one range may effect his stability factor at another. If he's shooting a 1 in 9 at 2775-2900 he should be fine at 1000.

Good luck,
Merritt </div></div>

Stability factor is always affected by the twist at a different range.

The static (gyroscopic) stability factor increases as the bullet goes downrange. As long as it is stable at the muzzle the gyroscopic stability increases as the bullet slows. The dynamic stability is where the question comes into play, and how it interacts in the overall stability inequality condition.

The dynamic stability can be low with a high static stability and the bullet appears to be overall stable.

This is exactly the condition of a 168 SMK 30c as it leaves the muzzle. The bullet is actually dynamically unstable by a small margin, but the static stability factor is high enough to make sure that the mild dynamic instability does not create a growing instability overall until the magnus effects really grow near the sound barrier.

OP- At 3000fps you're going to be fine, enjoy.

 

[Soren]

Re: 150 grain 7mm SMK @1000 meters

Regarding the .308 168 SMK's not stabilized at 1000yds. Don't believe it. The bullet comes in very steep at that range and when it hits the paper it only looks like it's keyholed. This comes from 2 instructors that I definetly respect.

 

[bohem]

Re: 150 grain 7mm SMK @1000 meters

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Soren</div><div class="ubbcode-body">Regarding the .308 168 SMK's not stabilized at 1000yds. Don't believe it. The bullet comes in very steep at that range and when it hits the paper it only looks like it's keyholed. This comes from 2 instructors that I definetly respect. </div></div>

It is dependent upon atmospheric conditions wether that bullet is stable or not.

At 1000yd the flight path declination angle on the bullet for a 1000' DA is 1.9-2 degrees on the 168 SMK 30c (launch velocity dependent). You won't see that on paper holes.

Additionally, my 6.5-06 declination angle at 1,740yd is appx 2.5 degrees and at that distance the bullet is still supersonic and still punching round circles.

They're likely seeing the slow arm of the epicyclic motion growing, but not going completely unstable at the paper where they shoot.

 

[Jon Lester]

Re: 150 grain 7mm SMK @1000 meters

162 A max does 1000 rather well in the 7-08 offering if you can shoot them.