Why do 168s get no love for 1000 yds?

[ReaperDriver]

I apologize if this has been gone through before but I notice that when ever a conversation about bullets and 1000 yds go together - either 175 or 155 weight bullets seem to get the most consideration. Why are the 168s usually left out?

In my very very low knowledge level - it appears that velocity and keeping the bullet supersonic is king to keep the shock wave from destabilizing the bullet in flight as it goes transonic. But if you keep a 168 supersonic, why would it perform any less than the slower 175s or the faster 155s?

Just wondering?

 

[sinister]

Re: Why do 168s get no love for 1000 yds?

The short boat-tail on the <span style="font-weight: bold"> <span style="color: #FF0000">168 Sierra Match King </span></span>doesn't cut enough induced base drag to keep the bullet supersonic past around 850 yards from a 24-inch barrel. As the bullet hits the trans-sonic zone the buffeting of the bullet against compressed air and the supsersonic shock wave will affect the bullet -- it won't end up where you aimed and wanted it to go.

Palma and long range shooters usually try pushing the 155 SMK at least 2900 fps from long barrels. The 175 has enough mass and a streamlined boat-tail to keep it supersonic past 1,000 out of 22-inch barrels. Shorter barrels will work as well if atmospheric conditions are cool and/or air pressure is low.

 

[kombayotch]

Re: Why do 168s get no love for 1000 yds?

That is specific to the 168 SMK and it's "clones". It isn't common to all 168 gr. 30 cal. bullets, but the reputation of the 168 SMK beyond 800 yards probably scares a lot of people away from 168s in general.

The 168 Berger VLD would work fine at 1000 yards. I believe the 168 AMAX is also ok. The 168 SMK can also work if you can keep it from going transonic...

 

[ReaperDriver]

Re: Why do 168s get no love for 1000 yds?

Thanks, those explanations makes more sense.

 

[Greg Langelius *]

Re: Why do 168s get no love for 1000 yds?

That's talking .308. I think it could be GTG with a .30-'06 chambering. I don't think it needs much more than what the .308 can provide before it becomes feasible for 1Kyd.

Why try the 168SMK in the .30-'06 for 1Kyd?

First, that's the .30-'06 Fed Gold Medal loading.

Second; recoil makes a difference for me, and I'd appreciate getting away without the recoil from the 175 and on up. Big difference? probably not, but I cut that corner as far as I can, just on general principle.

I don't have any .308's, just a .260 and a pair of '06's. I think those configurations make better use of the bore diameter and chamber capacities.

Greg

 

[sinister]

Re: Why do 168s get no love for 1000 yds?

An '06 would drive muzzle velocity up. A 300 Win Mag might be OK, too.

Going to the bigger powder capacity gives you the option to use a more efficient/aerodynamic bullet, though (175, 190, 200, or 210 Match Kings or Very Low Drag VLDs).

You'll be trading velocity for recoil and blast. You can mitigate some of that with a good brake.

 

[WillAdams]

Re: Why do 168s get no love for 1000 yds?

Most are talking about Sierra MK bullets not being able to stay supersonic/stable out to 1K in .308. Need to try the Hornady AMAX 168. Even with factory TAP ammo I can make good groups at 1K. Not all 168s are equal !!

 

[ReaperDriver]

Re: Why do 168s get no love for 1000 yds?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Will</div><div class="ubbcode-body">Most are talking about Sierra MK bullets not being able to stay supersonic/stable out to 1K in .308. Need to try the Hornady AMAX 168. Even with factory TAP ammo I can make good groups at 1K. Not all 168s are equal !! </div></div>
Yep, I'm REALLY happy with my 168 AMAXs so far. Haven't shot to 1K yet (soon) but they seem to be the most consistant from 100-600m in my gun so far.

On a side note, someone here made a comment that the 168 AMAXs (or maybe AMAXs in general) have a better than advertised BC. Anyone know what the real BC is if its different?

 

[Rob01]

Re: Why do 168s get no love for 1000 yds?

I always used the advertised BCs for the AMAX bullets and they are right on from my shooting expierience having shot them to 1000 and beyond although for those ranges from the .308 I would use the 178 AMAX and not the 168 AMAX.

 

[BOLTRIPPER]

Re: Why do 168s get no love for 1000 yds?


there is a member here that boosts 168AMAX to 1000yd and beyond ....and has kills at that range....but at a price....in a .308 he is blow-torching the throat to get there.

 

[Lindy]

Re: Why do 168s get no love for 1000 yds?

There is no point in trying to shoot a 168SMK past 800 yards, and Sinister's explanation about the boattail angle is correct. If you want to go past 800, <span style="font-style: italic">choose another bullet</span>.

 

[ReaperDriver]

Re: Why do 168s get no love for 1000 yds?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">There is no point in trying to shoot a 168SMK past 800 yards, and Sinister's explanation about the boattail angle is correct. If you want to go past 800, <span style="font-style: italic">choose another bullet</span>.
</div></div>
the explanation about the boattail angle is where it finally clicked for me, as I thought the issue was simply about velocity and keeping it supersonic long enought to stay out of the transonic region. I assume the 155 SMKs or 155 Palmas don't have that issue with the boattail angle?

 

[Criver600]

Re: Why do 168s get no love for 1000 yds?

Get decent spotting scope and compare the projectile's "trace". All the explanations (good) will come into focus when you see how the 168 flies....... Looks like a broken boat propeller. They are great out to 600 yards. Being they were designed for 300 meter competition thats pretty good.

 

[sinister]

Re: Why do 168s get no love for 1000 yds?

Palma shooters used to say "BC" when used in relation to the 155 Sierra Match King (product number 2155) meant "Ballistically Challenged." The NEW 155 Palma Match King (2156) has both a longer ogive and boat-tail.

Both should be pushed at 2900+ to keep them accurate at 1,000 yards.

http://www.sierrabullets.com/index.cfm?s...mp;displayAll=1

 

[Lindy]

Re: Why do 168s get no love for 1000 yds?

The B.C. of the Sierra 2156 155 is still well below that of the 175 SMK. There just is no reason to shoot the 155 unless you have to because of Palma regs.

 

[Queequeg]

Re: Why do 168s get no love for 1000 yds?

Lindy,

I'm not being impertinent here but why do you say the BC of the 155 is "well below" the 175? Is it due to the decline in velocity over the 1000 yard distance that you say this?

I just ordered 500 155s and am looking for schooling! I assume it's the 1800 - 2700 FPS range that is most applicable here.

The following list is from the Sierra site;


.308 dia. 155 gr. HPBT Palma MatchKing .308 155 Sectional density is .233

BC.s are
.504 @ 2700 fps and above
.470 between 1800 and 2700 fps
.430 between 1500 and 1800 fps
.380 @ 1500 fps and below

308 dia. 175 gr. HPBT MatchKing .308 175 Sec.Density .264
BCs are,

.505 @ 2800 fps and above
.496 between 2800 and 1800 fps
.485 @ 1800 fps and below

 

[WillAdams]

Re: Why do 168s get no love for 1000 yds?

Lindy, BS !! When you have over 2500 of the 168 AMAX and you have consistently hit 1K then there is A POINT to use them !! besides being broke and working 2 part time jobs ...

The AMAX IS NOT the SMK and that is MY Point. It Will reach 1K in a "normal" 308. Well about as normal as a T2K or a GAP can be. I'm using either N150 or IMR4895 and I'm also using hBN. Works for me.

 

[ReaperDriver]

Re: Why do 168s get no love for 1000 yds?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Will</div><div class="ubbcode-body">Lindy, BS !! When you have over 2500 of the 168 AMAX and you have consistently hit 1K then there is A POINT to use them !! besides being broke and working 2 part time jobs ...

The AMAX IS NOT the SMK and that is MY Point. It Will reach 1K in a "normal" 308. Well about as normal as a T2K or a GAP can be. I'm using either N150 or IMR4895 and I'm also using hBN. Works for me. </div></div>
What's your IMR4895 load with the 168 AMAX? Along with the other usual data for a load recipe.....

 

[MontanaMarine]

Re: Why do 168s get no love for 1000 yds?

In the 308 Win you can push the 168 SMK to 1000, sometimes, depending on your atmospheric conditions.

There are better choices that will yield less drift, more retained velocity, longer supersonic range, and more retained energy. Since those qualities are appealing to most long range shooters, the choice becomes pretty easy.

 

[Sig685]

Re: Why do 168s get no love for 1000 yds?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sinister</div><div class="ubbcode-body">(snip) Shorter barrels will work as well if atmospheric conditions are cool and/or air pressure is low. </div></div>

Really? I would have thought that <span style="font-style: italic">warm or hot</span> atmospheric conditions would allow the bullet to go faster.

 

[WillAdams]

Re: Why do 168s get no love for 1000 yds?

Reaper, PM to you

 

[sinister]

Re: Why do 168s get no love for 1000 yds?

It depends.

Hot, dry, and high altitude and your velocity is going to go up and your air will be less humid.

Hot and humid (Quantico in July and Camp Perry in August, or say Southeast Asia, Horn of Africa or Ivory Coast, the Caribbean, or equatorial South America) and your pressure may go up but you'll get drag from the higher air density.

 

[Lindy]

Re: Why do 168s get no love for 1000 yds?

Boy, what a mess of comments.

Queequeq: lower is lower. Run a ballistics program which uses multiple B.C.s, like Atrag or Exbal, and see what you get. Or check the G7 B.C. for the 155SMK versus the 175SMK which Bryan Litz computed - JBM has those in its bullet library.

Will: I never said anything about any 168 grain bullet other than the SMK.

But, for that matter, if someone was going to shoot a 155, the Lapua Scenar is superior to the Sierra.

And Sinister, higher humidity causes less dense air, and less drag, not more. Water molecules are lighter than dry air.

 

[sinister]

Re: Why do 168s get no love for 1000 yds?

Warmer/humid air has more molecules of water in it than air.

Pilots have to calculate density altitude performance differences for take-off and landing rollouts.

95F, 25% humidity, and 5,500 feet MSL is going to give a different bullet strike in Albuquerque than 95F, 99% humidity, and approximately 300 feet MSL at Quantico.

 

[doc76251]

Re: Why do 168s get no love for 1000 yds?

As long as the molecules of water are still a vapor they are lighter than dry air.

99% humidity is called a cloud.

Clouds float.

When they condense it's called rain and it falls, along with the humidity.

Cheers,

Doc

 

[Lindy]

Re: Why do 168s get no love for 1000 yds?

Dave: Air density is inversely proportional to temperature, directly proportional to barometric pressure, and inversely proportional to moisture content.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Humidity affects the air density, tending to decrease the air density a small amount, depending on the relative humidity in the atmosphere and the vapor pressure of water at the temperature of the atmosphere.</div></div>

From:

Sierra Exterior Ballistics - Atmospheric Conditions

 

[sinister]

Re: Why do 168s get no love for 1000 yds?

I stand corrected.

From Sierra:

Humidity also has a small effect on a bullet’s trajectory, and at all altitudes. Humidity affects the air density, tending to decrease the air density a small amount, depending on the relative humidity in the atmosphere and the vapor pressure of water at the temperature of the atmosphere. <span style="font-weight: bold">The effect of humidity is generally worst at locations near sea level on very hot days, but even under these conditions, the effect is small.</span> For example, for a location near sea level on a 90°F day with barometric pressure the same for both situations, absolutely dry air (zero relative humidity) is not quite 0.02 percent MORE dense than air saturated with water vapor (fog, meaning 100 percent relative humidity). This seems strange; wet air feels “heavier” than dry air. But it is true because a water molecule weighs less than a nitrogen molecule, which it displaces if the pressure and temperature remain the same. <span style="font-weight: bold">This tiny change in air density is not completely negligible for long-range shooting. For example, under these same atmospheric conditions, the drop at 1000 yards for Sierra’s .308” diameter 168 grain MatchKing bullet fired at 2700 fps muzzle velocity will be about 2.4 inches more for absolutely dry air than for saturated wet air.</span>

 

[Graham]

Re: Why do 168s get no love for 1000 yds?

I have pushed 168 factory SMK's to 1000 yards from a 26" bbl. They take about twice the wind as do my 175 VLD's at the same velocity - 2710fps. But the problem doesn't end there: I find that the 168's begin to get erratic well before they run out of gas, and well before they go transonic according my calculations. I'm not exactly sure why, but I have recorded consistency problems with their accuracy at ranges beyond 700 or so. It may be the boat-tail. It may also be other factors with regard to bullet design and/or manufacture. I'm not exactly sure.

 

[Lindy]

Re: Why do 168s get no love for 1000 yds?

Sometimes they work, sometimes not. If you live at Frank's altitude in Colorado, you're in luck - unless it's cold.

But why take a chance?

For LEO snipers, the 168 is the gold standard - and there may be good reasons including, but not limited to, department policies, for them to use them. As we know, though, LEOs mostly are shooting at shorter distances, where they will work.

 

[doc76251]

Re: Why do 168s get no love for 1000 yds?

One thing I have never understood about the 168's, specifically M-852 is that at 600 yards they are accurate and supersonic. At 1K they are also accurate and NOT supersonic. This being out of a 21" M1A/M14. Unfortunately I never shot the Palma course of fire to see if they would hold at 800 and 900.

I know for a fact they are NOT accurate (Minute of Target Frame, maybe) out of a sub MOA Winchester HBV at the Quantico 1K line on Any-Any day.

Cheers,

Doc

 

[Lindy]

Re: Why do 168s get no love for 1000 yds?

Relative humidity is an interesting phenomena which can be fun to contemplate, because moist air <span style="font-style: italic">feels</span> heavy.

People say, "Oh, the temperature was 100 degrees and the humidity was 95 percent."

No, it wasn't. Didn't happen, at least not on this planet. Lots of people believe things like that, though.

Doing a Google search on "what was the highest dew point" reveals some interesting information.

 

[JesseBB]

Re: Why do 168s get no love for 1000 yds?

It would appear that the U.S. Military establishment is aware of the short-commings of the 30 caliber 175 LR ammo for distances beyone 800 meters and that is why there are other larger caliber weapons are in our inventory. (.338 anyone)