Range Report Flatter shooting vs windage effects

[ReaperDriver]

I read the usual debate over the higher BC, lighter, flatter shooting bullets like the 155 Scenars vs the heavier, lower BC, slower bullets like the 178 AMAX.

MY question is: all thing being equal - which is going to be affected by the wind more?

I get the love for flatter trajectories, but to me - I would think I would want something that gets pushed around by the wind less would be preferable than a flatter trajectory. For me, the trajectory is fixed for a given condition - so who cares if its flat or more parabolic? As long as you have good dope - lofting a heavy bullet will still hit the target compared to a faster, flatter bullet. OTOH, a slower heavier bullet that gets pushed by the wind less to me seems more desirable. Running some quick calcs on JBM, for .308 - it seems like you have to get a 155 Scenar screaming fast (3000 fps+) for it to perform better in wind than a slower 175SMK or 178AMAX in the 2600-2650 range.

To me, trajectory is a known value I can dial for. Windage is the big unknown. Shouldn't I care more about wind than whether a bullet shoots flat or not?

Thoughts?

 

[Target In Sight]

Re: Flatter shooting vs windage effects

Tag~

Very interested to learn about this subject.

 

[Lindy]

Re: Flatter shooting vs windage effects

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Shouldn't I care more about wind than whether a bullet shoots flat or not?</div></div>

I'd think so.

That, by the way, is reflected in the BCs - not necessarily the manufacturers', but in Bryan Litz's tested ones. The 178 Amax has higher BCs than the 155 Scenar.

As he notes in his book, Applied Ballistics for Long Range Shooting,

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> In a trade-off between low BC (light weight) bullets at high speed compared to high BC (heavy) bullets at reduced speed, the high BC bullets at lower speed will produce less lag time and less wind deflection. </div></div>

 

[ChadTRG42]

Re: Flatter shooting vs windage effects

Reaper,

Your thoughts are right on. The distance that one bullet becomes more appealing over another is about 600 yards. The heavy bullets will drift less than the lighter (155) bullets beyond 600. The 155 at 1K will drift more. So, if most of your shots are 600 and less, the 155 is not a bad option. But, I opt for the heavy bullets for a good over-all distance and less wind drift. I generally know how far I'm shooting, so wind drift is my deciding factor.

 

[trigger time]

Re: Flatter shooting vs windage effects

Ok, lets say I'm running a 180 grain 7mm at 2800 fps that has a bc of .660 G1 against a 300 grain .338 bullet with the same bc of .660 at the same speed of 2800. Will the wind push the .338 bullet less than the 7mm due to a weight diff or will it be the same due to the fact the bc is the same?

 

[WRM]

Re: Flatter shooting vs windage effects

You would be plugging the same numbers into the same program, so you should get identical results, whether you use the G1 or G7 curve. However, these BC numbers are approximations, so real world results may vary.

Bill

 

[gugubica]

Re: Flatter shooting vs windage effects

ALL else being equal (BC, velocity), yes, a heavier object will be affected less by outside forces (wind). But, the BC of a bullet will also dictate how well a bullet resists wind deflection.

The caveat is that BCs change with velocity. So, two projos with the same BC will perform very differently as the velocity decreases at different rates. There is the rub. Heavier projos are harder to get going as fast, and if you start slower, you slow down slower too.

The shape of a bullet has a large effect on this as well. aside from construction material, to make a projo heavier while retaining diameter, it has to get longer.

BC is not the whole story, weight is not the whole story, boat tail is not the whole story, etc.

There are a mind-blowing amount of of factors that go into which bullet is the better for a particular situation. As far as I am concerned, there is only one man on Earth that actually understands it all. Bryan Litz.

 

[azimutha]

Re: Flatter shooting vs windage effects

Since all trajectories are ballistic, you're right that windage can be more important since it's much easier to correct for drop (with any decent scope/mount that has enough travel). A couple of disadvantages sometimes of heavier projectiles, however:

1) somewhat greater recoil
2) bullet shape may make seating difficult since they can end up really long for caliber occasionally.

Another advantage though for big game hunters: more retained energy. Since He-Who-Must-be-Named-in-any-Ballistics-related-Post has already been mentioned twice in this thread, I will add that Litz posted on another forum that he wished all his Palma competitors would stick to lighter bullets.

 

[MitchAlsup]

Re: Flatter shooting vs windage effects

When I plug in ::

175 SMK (Litz) and 2650 fps: I get 10.9 windage; 1.748 seconds; energy 482; at 1000 yards
155 Scenar (litz) and 2950 fps: I get 9.4 windage; 1.552 seconds; energy 552; at 1000 yards

{into JBM, rest of the parameters were left alone}

I'm not seeing the "less deflection" here, or less down range energy, or the lighter bullet taking more time.

 

[azimutha]

Re: Flatter shooting vs windage effects

I do when I compare two bullets that are closer in weight (e.g. 165 gr. vs. 180 gr. Accubonds) and in velocity. With loads that both shoot accurately, I can get 2750 out of the 165s and 2660 out of the 180s.

At 1000 yards:
165: 2.6 mils windage, 1.588 seconds, energy 617.1
180: 2.5 mils windage, 1.599 seconds, energy 699.4

If you can drive a bullet that's 20 gr. lighter 300 more fps then, by all means, that's the way to go.

 

[Willys46]

Re: Flatter shooting vs windage effects

I'll jump in really quick with my first hand experience (which is not much).

Shooting two different guns, 6.5 X284 and a 7 rem mag.

7 rem mag shooting 168 VLD @ 3050--BC .617
6.5X284 running 140 VLD @ 3075--BC ..615

these two run almost identical out to 1200 yrds (within shooters capabilities) I do not think at a 1000 yards my accuracy can tell .25 moa!

What you find is most heavy bullets come with a higher BC, making them a better choice, if you can push them to acceptable velocities.

 

[Chanonry]

Re: Flatter shooting vs windage effects

Reaper,

Your thoughts are right on. The distance that one bullet becomes more appealing over another is about 600 yards.


Depends on what you are comparing.

I have been looking at my 308 hunting load. Fed Sp 150gr whacks everything out to 350/375 beyond that they run about a bit more. Running the ballsitics, this is because the velocity drops below 1800 fps at about that range so presumably it doesn't expand as well, as well as having less energy. If I switch to a 200gr head (with RL17) I can push that velocity hurdle out to 600 yds

 

[Greg Langelius *]

Re: Flatter shooting vs windage effects

I've tried to reduce this stuff to a minimum common denominator, and the value I keep coming up with is time of flight. Whichever bullet arrives sooner usually does it with less drift.

Greg

 

[ReaperDriver]

Re: Flatter shooting vs windage effects

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body">When I plug in ::

175 SMK (Litz) and 2650 fps: I get 10.9 windage; 1.748 seconds; energy 482; at 1000 yards
155 Scenar (litz) and 2950 fps: I get 9.4 windage; 1.552 seconds; energy 552; at 1000 yards

{into JBM, rest of the parameters were left alone}

I'm not seeing the "less deflection" here, or less down range energy, or the lighter bullet taking more time. </div></div>

yes, you're correct. But the caveat is you have to get the 155's going fast enough to overcome their lighter weight. For those of you who can/want to get 155's up to 2950-3000 fps, yes - you will probably see a slight advantage. Unfortunately, I've tried both 155 SMK and Scenars and with my 20" tube - I've only been able to get them into the high 2700's to low 2800's before pressure signs. I've also shot them at 1K at those speeds and I get quite a lot more drift than the heavier 175/178s.

Also, I gotta think you're barrel life at 2950 speeds is going to degrade rather quickly.

 

[Lindy]

Re: Flatter shooting vs windage effects

The 155 Scenars are popular with the F-class FTR crowd - but they're shooting them out of longer barrels, some I've seen of 30 inches.

Speed matters, as you note.

 

[knockemdown]

Re: Flatter shooting vs windage effects

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gugubica</div><div class="ubbcode-body">ALL else being equal (BC, velocity), yes, a heavier object will be affected less by outside forces (wind). But, the BC of a bullet will also dictate how well a bullet resists wind deflection.

</div></div>

I don't believe the first sentence is an accurate statement.

If the two bullets truly do have an identical b.c., when launched at the same speed, their trajectories will be exactly the same. That is precisely what a b.c. standard is all about...

 

[JRose]

Re: Flatter shooting vs windage effects

I prefer heavier bullets myself, but remember, there's always a happy medium...

Think of the old drag car debates. Big block heavy torque monsters vs. light weight ricers. Both are fast as shit, both have equal merit, but there comes a point where one just takes over the other either way.

 

[MitchAlsup]

Re: Flatter shooting vs windage effects

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">I've tried to reduce this stuff to a minimum common denominator, and the value I keep coming up with is time of flight. Whichever bullet arrives sooner usually does it with less drift.</div></div>

I agree completely, with one minor caveat:

If both bullets take the same amount of time, the heavier bullet will have a tiny amount less drift.

 

[WRM]

Re: Flatter shooting vs windage effects

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: knockemdown</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gugubica</div><div class="ubbcode-body">ALL else being equal (BC, velocity), yes, a heavier object will be affected less by outside forces (wind). But, the BC of a bullet will also dictate how well a bullet resists wind deflection.

</div></div>

I don't believe the first sentence is an accurate statement.

If the two bullets truly do have an identical b.c., when launched at the same speed, their trajectories will be exactly the same. That is precisely what a b.c. standard is all about... </div></div>

+1. Weight is already figured into the BC. BC and speed are the only two things the program uses to calculate trajectory, it only needs weight to do energy. Look at how the Speer manual lists trajectory tables - they have tables for different BCs, and then tell you which bullets are "in that group"; for energy, they give you ft-lbs/gn, so you can multiply by bullet weight.

Comparing 155s @ 2950 (2995 Ft-lbs) and 175s @ 2650 (2728 Ft-lbs) is not a fair comparison. You have to start them with equal energies.

2861 Ft-lbs:
155 = 2883 fps
175 = 2714 fps

Then tell me which has less drift....

Cheers,

Bill

 

[spotter300]

Re: Flatter shooting vs windage effects

My load for F class T/R is 155 Lapua's Scenars @ 2800 fps. I shot a 94-3x @ 500 meters. My barrel is only 24 inches long 1:10 twist. This pass Saturday was my first time loading Lapua pills. They shot fine for me. I going to keep load testing with them. I was happy with a 4th place out of 25 shooters. However, I plan on dumping another .5 of powder and see how they do at the Texas Mid range Championship next month. Scenars have a B.C of .505. However, dont get to caught up in the B.C. The B.C wont matter if your rig doesnt like the bullets. The Scenars are longer than the 155 Amax. My OCL in 2.820 and I am out the lands by .010. Your rig my like 155 Amax's better than the Scenars.

 

[Bronco]

Re: Flatter shooting vs windage effects

WRM / Bill
Your suggestion is very close to my actual loads.
175 smk @ 2720
155 scenar @ 2890
RSI shooting lab agrees with my field experience that the 155 scenar have a 1 moa edge over the 175 smk at 1000 yd (10 mph full value wind). I shot the 175's until I built a rifle throated for the 155 scenar. Have stuck with the 155's. And for Greg time of flight is 1/10 of a sec. faster with the 155's.

 

[MitchAlsup]

Re: Flatter shooting vs windage effects

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WRM</div><div class="ubbcode-body">

Comparing 155s @ 2950 (2995 Ft-lbs) and 175s @ 2650 (2728 Ft-lbs) is not a fair comparison. You have to start them with equal energies.</div></div>

Can you explain why?

I can get my 155s up to 2950 fps, I might be able to get 175s in the same gun up to 2675, but there is no way, at sane pressures, to get the 175 up to 2775 fps to match the 155s Muzzle energy.

It seems to me, that what you advocate, is to penalize the light high BC bullets inorder to (ahem) 'fairly' compare them to the 175 SMK !?!?!

 

[rmfield]

Re: Flatter shooting vs windage effects

MitchAlsup, you are right on. Muzzle energy means nothing unless you're only looking to shoot your rifle at point blank range. What is important is the drift, drop and energy at the range of your anticipated targets.

With modern laser rangefinders, drop is much less important than it was considered to be 20 years ago. Hunters are learning that high BC doesn't just mean less wind drift, it means more retained energy, too.

Brian Litz covers this topic well in his book and I highly recommend it.

 

[Lindy]

Re: Flatter shooting vs windage effects

Second the nomination for Bryan's book, Applied Ballistics for Long Range Shooting

 

[knockemdown]

Re: Flatter shooting vs windage effects

The point I was trying to make that WRM agreed with was that same b.c. bullets, when launched at the same velocity, will have the same flight characteristics, regardless of caliber.

For example, assume these b.c.s have been proven true:

a 30gr .17 caliber GOLD, G1 b.c. of .27
a 55gr .243 caliber Nosler BT, G1 b.c. of .27

A .17Predator can launch that 30gr Gold @ 4000fps.
A .243Win can launch that 55gr NBT @ 4000fps.

Given the identical b.c. and muzzle velocity, they will exhibit the same drop & drift characteristics. The actual weight of the bullet is of no consequence. Run the #s on a ballistic calculator to see for yourself...
You will note that, thanks to the increased mass of the .243 caliber NBT, it will retain more ENERGY at distance than the lighter mass of the 30gr GOLD. But again, they will both share the same drop & drift values...

 

[WRM]

Re: Flatter shooting vs windage effects

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WRM</div><div class="ubbcode-body">

Comparing 155s @ 2950 (2995 Ft-lbs) and 175s @ 2650 (2728 Ft-lbs) is not a fair comparison. You have to start them with equal energies.</div></div>

Can you explain why?
</div></div>

Be glad to.

Given similar construction, I've often used equivalent ME when working up new loads, with good results (Bryan does the same thing when comparing various bullets in his book). I actually believe many cartridge cases are more "efficient" with heavier bullets (assuming equal peak pressure), because the charge has more time to act on the bullet (longer dwell).

To work up some light-recoil loads for HP Silhouette in a Ruger M77VT 308 Win, I wanted a muzzle velocity of ~2400 fps for both 168 MKs (Chickens, Boars, Turkeys) and 190 MKs (Rams). The exact same powder charge got the 190 MKs to 2400 fps, and the 168s to 2410 (statistically "damn close"), and they shot to the same POI at 100 yards. That's a significant ME advantage to the 190 MKs, and much more "efficient" use of that powder charge? I actually took that 2400 fps 190 gn load to 1000 yards in Pella, IA and managed a couple sub-moa 5-shot groups with that rig (it probably averaged around 15").

Because there are so many "Interior ballistic" variables (powder burn rates, primer temperature, bullet bearing length, thickness, and material, etc.), there may be "exceptions", but I've found that this generally holds true.

Cheers,

Bill

 

[MitchAlsup]

Re: Flatter shooting vs windage effects

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WRM</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WRM</div><div class="ubbcode-body">

Comparing 155s @ 2950 (2995 Ft-lbs) and 175s @ 2650 (2728 Ft-lbs) is not a fair comparison. You have to start them with equal energies.</div></div>

Can you explain why?
</div></div>

Be glad to.</div></div>

You still did not explain why::
A: if I can get a 155 up to 2999 ft-lb ME (2950 fps)
and
B: I can only get a 175 up to 2833 ft-lb ME (2700 fps)
that
C: I should download the 155s
for a "fair" comparison.

 

[WRM]

Re: Flatter shooting vs windage effects

Make whatever comparison you want, I really don't care.

 

[johndoe]

Re: Flatter shooting vs windage effects

This is good stuff !!

 

[softcock]

Re: Flatter shooting vs windage effects

(Michalsup),Your thought line is correct and WRM's also is correct . In your original Post the main Q-? asked was ..." <span style="font-weight: bold"><span style="font-style: italic">To me, trajectory is a known value I can dial for. Windage is the big unknown. Shouldn't I care more about wind than whether a bullet shoots flat or not</span></span>? ". Thoughts?
(wrm) Talking pure #'s and only with bullet weight and all equal, Ya weight is king for BC and windhold . But on your line of thought and with the variables of parent case, tube length and what you limited too with all when firing from a .308 & that is what you are coming from . When using the comparison that you are making then that your equipment (tube and brass) being the control base for comparison. then you are correct by your limitations put to the bullet weight & BC on the range . The 155's @ 3-k walk on the 175's @ 2800 out a .308 .
Just saying (my thoughts) that you both are looking correct . but when you take your original Q in the 1st post and apply pure simplicity & fact for the correct answer. Then ( Greg L) ... "<span style="font-weight: bold"> Whichever bullet arrives sooner usually does it with less drift.</span>" .
.

 

[GuinnessNM]

Re: Flatter shooting vs windage effects

Let the numbers decide. Using Bryan's free ballistic program and his G7 b.c.'s with velocities I actually obtain for handloads, at 1000 yard range for southern NM conditions:

Berger 155.5gr fullbore 2850fps G7=.237
drop 305in
dh/dR 8.5in/10yd
drift 76.8in/10mph
velocity 1430fps
lethality 106 lb

Berger 175gr LRBT 2710fps G7=.264
drop 322in
dh/dR 8.7in/10yd
drift 71.4/10mph
velocity 1450fps
lethality 141 lb

Berger 210gr LRBT 2540fps G7=.320
drop 340in
dh/dR 8.8in/10yd
drift 61.4in/10mph
velocity 1514fps
lethality 230 lb

This says that the difference between 155's and 175's of similar type is not worth discussing. Mis-doping the wind by 1.2mph has about the same effect as misdoping the range by 10 yards - both produce an 8" miss. 175's have a slight edge in lethality (this is a forum about Sniping, not paper-punching right?) Out to 600 yards the differences are even less pronounced.

At 1000 yards the 210's should perform better.

 

[MitchAlsup]

Re: Flatter shooting vs windage effects

What would the numbers above look like if the 155s were launched at the more typical 2950 fps?

 

[GuinnessNM]

Re: Flatter shooting vs windage effects

Berger 155.5gr fullbore 2950fps G7=.237
drop 280in
dh/dR 7.8in/10yd
drift 72.0in/10mph
velocity 1502fps
lethality 122 lb

But how typical is 2950 fps? I am getting pressure signs (light extractor marks) at 2850fps for the 155 grainers and the 210 gr. loads, but no pressure signs for the 175 grainers. I could push the 155's harder, but I could also push the 175's harder.

Also these differences are still tiny. To hold within +/-8" horizontal of the POA with the hot 155 load requires reading the wind value with a precision of +/-1.1mph, and for the 175's with a precision of +/-1.05mph. No practical difference. To hit within 8" vertical for the 155's one must range within +/-10.2 yards and for the 175's within +/-9.2 yards. The difference in precision is within the error of the range finder. There is no practical difference among these loads for real-life shooting - form the POV of ballistic performance. For me this is a Ford vs. Chevy argument. Shoot what you and your rifle like.

The 210gr loads show more promise beyond 600 yards, because they are the highest ballistic coefficient bullet available in 308 caliber which can be propelled with enough velocity. The problem is that the 308Win case is undersized for the caliber. It won't hold enough powder to really exploit these heavier bullets.

 

[MitchAlsup]

Re: Flatter shooting vs windage effects

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GuinnessNM</div><div class="ubbcode-body">But how typical is 2950 fps?</div></div>

I am getting 2925-2950 fps from 47.8 gr Varget pushing 155 scenars in Win cases and CCI primers in a 24" tube. OAL is 2.943 with a 0.015 jump in a 2.968 throat.

Is this typical? I prefer to take the position that this load is right on the edge of sane pressures. I have squared off edges on the primers, but no other pressure signs, and have at least one batch (100 cases) of brass (Win) with 24 load cycles without loosing a primer pocket (or crack or other pressure sign). QuickLoad puts it at 62K PSI. I suspect the long OAL and long throat contribute to the lack of other pressure signs. Every once in a while I get an extractor mark (like 1 case out of 100 every three reload cycles).

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> Also these differences are still tiny. To hold within +/-8" horizontal of the POA with the hot 155 load requires reading the wind value with a precision of +/-1.1mph, and for the 175's with a precision of +/-1.05mph. No practical difference. To hit within 8" vertical for the 155's one must range within +/-10.2 yards and for the 175's within +/-9.2 yards. The difference in precision is within the error of the range finder. There is no practical difference among these loads for real-life shooting - form the POV of ballistic performance. For me this is a Ford vs. Chevy argument. Shoot what you and your rifle like.</div></div>

I am in complete agreement with you here. For the very most part, knowing the ballistics of your load and reading the distance & conditions contributes more to the overal success rate than the difference between one loading and another. This goes 5X for when you might only have one chance to make the hit.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The problem is that the 308Win case is undersized for the caliber. </div></div>

Yes, it is; but it is what is is (to quote Popeye).

To me, its a miracle that one can get the 308 to shoot out into the 1300 yard range (independent of what bullet one chooses)
AND
If you really want more (yardage, energy,...) and have to (or want to) stay inside 30-caliber the 300WM is the better choice.

 

[TresMon]

Re: Flatter shooting vs windage effects


Yeah,

F class T shooters as well as NRA Palma competitors shoot 30 & 32" barrels.And it was reported back to me from Camp Perry Nationals that that AMU team members were shooting 155's @ over 3K fps.

But I still think if I were shooting I'd want a 175, 180 or even 190 @ 32" velocities instead of a 155 @ 32" velocities. Also Barrel length and added velocity is not free. You occasionally "loose a bullet" with a long barrel. They get so hot from bore time that the lead core liquefies and the bullet separates before it get's to the target....

 

[GuinnessNM]

Re: Flatter shooting vs windage effects

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body">

I am getting 2925-2950 fps from 47.8 gr Varget pushing 155 scenars in Win cases and CCI primers in a 24" tube. OAL is 2.943 with a 0.015 jump in a 2.968 throat.

</div></div>

I'm using N150 for the 155's and Varget for the 175's. Sounds like I should try Varget for the 155's.

How hard have people pushed the 175's? Loaded to the same average pressure producing the same muzzle energy, the heavier bullet with same G7 form factor should have slightly better windage values at long ranges. To get the same m.e. as the 2950fps 155gr load, the 175's need 2775fps muzzle velocity.

 

[ASU1911]

Re: Flatter shooting vs windage effects

Someone spell this out for me.

What does "energy" have to do with anything?

 

[GuinnessNM]

Re: Flatter shooting vs windage effects

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ASU1911</div><div class="ubbcode-body">Someone spell this out for me.

What does "energy" have to do with anything?</div></div>

If the internal ballistics are equally efficient, then all 308 bullets irrespective of the bullet weight should reach the same muzzle energy assuming the same average chamber pressure and barrel length. This statement neglects effects such as barrel friction, which depends upon the contact area between the barrel and the cylindrical part of the bullet, but it is basically true. If people are not getting about the same muzzle energy for 175gr bullets as for 155 grain bullets, then the powder is not optimized. Maybe it is too fast or too slow. So the starting point for comparing the theoretical performance of different bullets is to assume they are loaded to the same muzzle energy ME = 1/2 * m * v^2 = P*A*d, where m is the bullet mass and v the muzzle velocity (squared), P is the average chamber pressure, A is the cross-sectional area of the bore, and d is the barrel length, expressed in the right units.

My 155gr 2850fps loads, and my 175gr 2710fps load have about the same muzzle energy. Thus I expect that if it is possible to push the 155's faster, the 175's could also be pushed faster, and the 175's would still beat the 155's for wind deflection by a tiny amount of no practical importance.

But this is a technicality. Anyone can run the ballistics codes for chronographed real-world velocities and see that there is very little performance difference between 155 grain and 175 grain 308Win loads.

I looked at many different bullets on the market, using Bryan Litz's b.c.'s and found there are larger performance difference among match bullets of the same weight, such as 175SMK compared to 175 LRBT, or Sierra Palma vs. 155.5gr BT, than between 155's and 175's of similar construction - for real world velocities for my loads fired from my rifle, not just theory. In my experience for accurately measured parameters (ballistic coefficient, muzzle velocity, scope height, atmospherics, scope clicks calibrated) Bryan Litz's ballistic code is right on, so I believe the results.

 

[TresMon]

Re: Flatter shooting vs windage effects


And continued responce for ASU 1911/energy;

I do all my predator & deer hunting with my .223 AR. Sierra Bullets Smiths (800-223-8799) establish "about" a 700 ft.lb. threshold to cleanly & ethically kill the White Tailed deer. Thats for John Q public that happens to reload. Myself being at least a .5% better shooter than John Q, and shooting said deer in the neck- I have found from repeated & repeated real world shots that 400 ft. lbs. delivered to the neck flips them off like a switch. So what does energy have to do with anything? When I work up a new load or bullet in my AR, I can run the ballistic math and know the outer limit/range of that load to ethically make a clean, one shot kill on a whitetail.

 

[Jedi]

Re: Flatter shooting vs windage effects

for any given barrel length
given 155 scenar and 175smk have roughly same bc

the faster bullet should be better
less time of flight equate to less effect from wind etc

I routinely ran 155scenars @ 2975fps from 26" rock 5R

but having said that i no longer shoot 308 period

6.5x47
only now
almost like cheating fast 6/6.5 are hard to beat
YMMV

 

[ASU1911]

Re: Flatter shooting vs windage effects

Your velocities for the 175 are high and your velocities for the 155 are low.

Lapua sells a load for the 155 that goes 2840, but you won't see factory loads for the 175 that go that fast unless you are talking about the new Hornady ammo, which uses a different propellant.

So I don't see how all that math is of any consequence.

As for terminal effect, I always thought that estimating the diameter and depth of the wound cavity was more appropriate, especially considering that some bullets with the same "energy" have radically different performance on tissue.

 

[TresMon]

Re: Flatter shooting vs windage effects


No energy is not everything. DELIVERED energy is everything. A bullet can be carrying 5 tons of energy, but it it's a fmj that zip right through it delivered hardly any energy on target.

But let's say you have an average EXPANDING bullet carrying realistic energy numbers, that does not pass through. You have delivered 100% of the energy on target. That's where it's at.

 

[Downzero]

Re: Flatter shooting vs windage effects

Neither energy nor delivered energy really matters. What matters is the wound it creates. Energy is related to that, but they are not the same thing.

 

[TresMon]

Re: Flatter shooting vs windage effects

Respectfully & totally disagree. Thanks. Good day.

(It's Energy that gel's organs & tissue FAR BEYOND both the temp & permanent wound cavity.)

 

[softcock]

Re: Flatter shooting vs windage effects

Ya your 155 Vel. is a little slow . I am getting 3020 fps with no presure signs with 155 berger .46.5 #15 . using 26.5 inch barrel . It's very easy & I know guys to push tham 3100 +plus Vel. with 30 inch barrels .
You are correct & it is like cheeting & you are a Big Cheeter . you are & also correct using on the 6.5x47L if you are moving out of the .308 . but if you run the #'s on the preferred top 3. ( .243 - 6.5x47L - .308 & 155's ) . The .243 with 115's is the Top Dog with the wind .

Not you jedi , but Why are we drifting to Energy & wound channels and gelling out organs and shit ? I thought the topic was Windhold & flatshooters to the POI ?
.

 

[TresMon]

Re: Flatter shooting vs windage effects


Sincere apologies...

 

[softcock]

Re: Flatter shooting vs windage effects

No need to apologize to me as I am just a dipshit who just really prefers to Lob the 175's like I was playing the game of Golf. & I often compare the two together because I imagine that Golfers must have the same fun. They call the wind and then Lob and do the Big Arch to drop it in on the POI they call.
Shooting 175's @ 2600 vel. is just plain relaxing & I kind of carry a underlying resentment on the fact that I have to run another separate rig with the 155's @ 3-k just to play on the upper curve of the game. I will always keep & never change my favorite .308 rig, keeping it pure & doing the 175's but I will becoming a cheater someday & convert over my .308 155 rig to the 6.5 0r .243 .
.

 

[Grump]

Re: Flatter shooting vs windage effects

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GuinnessNM</div><div class="ubbcode-body">But how typical is 2950 fps?</div></div>

I am getting 2925-2950 fps from 47.8 gr Varget pushing 155 scenars in Win cases and CCI primers in a 24" tube. <span style="font-weight: bold">OAL is 2.943 with a 0.015 jump in a 2.968 throat.</span>[emphasis added]

Is this typical? I prefer to take the position that this load is right on the edge of sane pressures.
[snip]
Every once in a while I get an extractor mark (like 1 case out of 100 every three reload cycles).
</div></div>
Unless those fit in your magazine, I hereby declare your loads as silly as those long 80-grain loads in .223 which NEVER should have been allowed in "service rifle" competition, regardless of the single-load rule.

In my own mind, at least.

Magazine length rules. Unless it's service rifle, YOUR magazine is the one that counts...

 

[ArcticFun]

Re: Flatter shooting vs windage effects

For wind drift take a look at the second law of physics (I think). The one dealing with inertia, or simply put: An objects tendency to keep going, or stay in place. We all know moving 5lbs is harder than moving 4lbs. It's just common sense (obviously the same sized or proportionally sized object). So what I would assume is that it takes more force to move an heavier object than a lighter object even if it is already moving. Say the wind is hitting two bullets at a 90 degree angle. They are of the same size and shape (or proportionally sized) yet the difference in weight is say 7grs (imagine .308 168gr and 175gr VLDs). The 168 gr pill is lighter and requires less force to move it perpendictular to it's course than the 175gr pill does. An object has inertia at all times and will always require force to move it. The amount of force needed is determined by the weight. Realistically having to correct for 6" more wind drift at 1K seems like a small amount to me. That's 2 clicks and a tiny hold. Now a 24" correction is much different. I'd go with a heavy bullet over the smaller one but that's just me.

 

[softcock]

Re: Flatter shooting vs windage effects

..." <span style="font-weight: bold"><span style="font-style: italic">Magazine length rules. Unless it's service rifle, YOUR magazine is the one that counts</span></span> " .
big+ on that on also .
You are Correct it's silly .If you are going to run 155's you need to just take the big commitment that you will Only run 155's in that rifle. Get a Reamer and Chamber-up specifically for Only 155's & Chambered-up specifically to fit in the internal your Mag. Box . You will be Married to the 155's in that Rig & you will in no way be able to the 175's unless you set them way deep in the boiler room @ that point . But that does not matter as it's all about the right tool & building it the right way .
.