Why is it better to have a "flat shooting" round?

[Notso]

Here's my dumb question of the day...... why is there so much emphasis placed on needing a "flatter" shooting round over one that is not when shooting known distances for target shooting, steel, tac matches, etc.? Let's leave wind drift aside for the moment. So if I'm shooting on a 1000 yd range with a .308 and a 6.5x47 side by side, why is the flatter shooting 6.5 better? With known ballistics of both, I should be able to dial in either one and hit the target. Does it matter that the 6.5 only needs 8.2 Mils and a .308 needs 10.2 Mils? They are going to both hit the steel in the same spot.

I get for UKD and for wind drift, these "flatter shooting" rounds are better. But I don't see what the ballistic trajectory has to do with anything. What am I missing?

 

[eracer]

To my understanding, the main benefit is:

1. Maximum Point Blank Range covers a longer distance. MPBR is the distance from the muzzle that one can hold center of the target and expect to impact the target within a given vertical dispersion. For military applications, that means the range in which the soldier can hold center mass, and expect the shot to impact the torso. For a deer hunter, it might means the range in which the shooter can hold on the top of the heart and expect the bullet to impact in the vitals. For a varmint hunter, the MPBR is much shorter, as the 'kill zone' is much smaller.

For each of those cases, the MPBR varies depending on the exterior ballistics of the round. Take the prairie dog hunter for example. With a .22 LR the MPBR might be 75 yards. With a .22/250 it might be 250 yards. Why? Because the .22/250 is a much 'flatter' cartridge, and the vertical dispersion is much less with any given hold.

You are correct when you say the flatter shooting cartridges don't really matter when you dope a rifle and adjust elevation for yardage - unless you're talking about really long ranges that have you running out of elevation on your optic.

 

[anthonylapoint]

Accuracy bud. Maybe not a big difference at only 1000, but a more stable round will be more accurate. Of course, wind drift is a large factor too. Taking that out of the equation is taking out half the reason.

 

[Notso]

Accuracy bud. Maybe not a big difference at only 1000, but a more stable round will be more accurate. Of course, wind drift is a large factor too. Taking that out of the equation is taking out half the reason.

How is a "flat cartridge" more accurate or stable than one that isn't "flat" shooting? I think you are missing the point of the question.

And yes, I get wind drift is a big part of the equation. I'm only taking it out for the sake of discussion of why people want the holy grail of a "flat shooting" round. Trust me, I completely understand the practical value of a round with a higher BC, higher MV, less wind drift, etc. But that wasn't what I'm asking about.

Is it just that people misuse the term "flat" as a catch all phrase when describing a better performing caliber?

 

[dimar1492]

Ok, let's talk terms of velocity spread. At a given distance of let's just say 1000 yards. And with your reloads you are getting the same consistency for both rounds of around 15fps ES. The faster moving bullet with the higher BC will be less affected vertically on target. Same with environmental conditions. If the DA changes throughout the day the slower moving .308 will be affected a little more. It's a percentage thing,if a you have a condition that causes a 2% shift in elevation to get on target that 2% equals a smaller number on the flatter caliber because it took less elevation to get there in the first place. All of the little things will affect a .308 worse than a flatter shooting caliber. Check it on a ballistic calculator at 1000 yds. Punch in your favorite .308 load at a given velocity then add 20 fps record the difference in inches at 1000. Then do it with a flatter shooting caliber and record the difference which will be less. Now, the difference between the two sums is how much more the.308's group would have grown vertically or how much further the hit would be from center or point of aim.

As you requested,wind drift left aside. As that is only one reason people score higher with flatter shooting calibers

 

[Blackbrush]

Ranging errors and come up solution errors have less effect on a flatter round.

If all you ever do is shoot at known distances on a known range, no big deal. If you shoot in the real world at actual soft and hard targets in unknown environments, then flatter is better.

 

[Pinecone]

If you know that the target is really 1000 yards. You can dial in the dope and get a hit.

But what happens if the target is actually 1010 yards?

The flatter shooting round will drop less from 1000 - 1010 and may still get the hit. The less flat shooting round is in a serious downward path, and a slight ranging error could cause a miss.

Also, flatter shooting typically means less time of flight, so less wind drift.

 

[agbm]

#1 Remember that there is never a dumb question!!!

First example: same Cal bullet but diff. BC's/weights. Higher BC bullets equal's flatter shooting. Take Sierra's .308 for example, .308 dia. 175 gr. HPBT Match King 0.308 175 .264 BC's .505 @ 2800 fps and above / .496 between 2800 and 1800 fps/ .485 @ 1800 fps and below With Federal's 175 FGMM out of my 20 inch barrel at MV 2510 FPS it takes me approx. 43MOA to reach 1000 yards just say .470 BC

Now check out this bullet which is GSCustoms 137Gr solid copper in .308 cal:GS CUSTOM BULLETS - 308137SP157 Technical Data lighter bullet/ longer bullet/ real high BC/ solid copper just a little bit more money!!!! .461 BC MV 3200 FPS it takes me approx. 24.50 MOA. I am still working on this load out of my 20 inch barrel to hit a target at 1000Yards.

Now when you compare those two setups, there is a difference of 18.50 MOA, that is a lot of MOA!!! Remember Solid Copper bullet's are a lot flatter shooting because longer equals higher BC. Sometime you just need to change the type of bullet and not the caliber to get there.

Second example 6.5SAUM Berger 130Gr BC .552 at 3300 FPS to get to 1000yards need approx. 20.5 MOA
Do a flight path of the 6.5 X 47 and the 308 and you will see how high the 308 goes up and has to drop down.

I want to be able to shoot a mile and hit the target more times than missing, so the 6.5SAUM would be a lot better choice over my 308 Win.
Less MOA the better because you have a less chance of wind and elements affecting the bullet.
Hope this helps!!!!

 

[BoilerUP]

Why is it better to have a "flat shooting" round?

Is it really fair to compare a 175 Matchking to a South African made solid bullet that costs $81.49 USD per hundred after converting from RAND?

 

[dimar1492]

Remember that there is never a dumb question!!!

First example same Cal bullet but diff. BC's. Higher BC bullet to me equal's flatter shooting. Take Sierra's .308 for example, .308 dia. 175 gr. HPBT Match King 0.308 175 .264 BC's .505 @ 2800 fps and above / .496 between 2800 and 1800 fps/ .485 @ 1800 fps and below With Federal's 175 FGMM out of my 20 inch barrel at MV 2510 FPS it takes me approx. 43MOA to reach 1000 yards just say .470 BC

Now check out this bullet which is GSCustoms 137Gr solid copper in .308 cal:GS CUSTOM BULLETS - 308137SP157 Technical Data lighter bullet/ longer bullet/ real high BC/ solid copper just a little bit more money!!!! .461 BC MV 3200 FPS it takes me approx. 24.50 MOA. I am still working on this load out of my 20 inch barrel to hit a target at 1000Yards.

Now when you compare those two setups there is a difference of 18.50 MOA, that is a lot of MOA!!! Remember Solid Copper bullet's are a lot flatter shooting because longer equals higher BC

Second example 6.5SAUM Berger 130Gr BC .552 at 3300 FPS to get to 1000yards need approx. 20.5 MOA

I want to be able to shoot a mile so the 6.5SAUM would be a lot better of my two choices

Hope this helps!!!!

I've heard that GS's BC's are inflated quite a bit.

 

[rrflyer]

With that price it'd still be cheaper to rebarel to a 6.5 and shoot amaxs.

 

[agbm]

I've heard that GS's BC's are inflated quite a bit.

I ordered some of the 137gr bullets, got to put them to a test very soon out to a 1000 yards. I can not say if they are inflated, but I will find out very soon. Also look at the 14.9mm SOP, it uses the GSC bullet all 1690grains of it.

 

[agbm]

Is it really fair to compare a 175 Matchking to a South African made solid bullet that costs $81.49 USD per hundred after converting from RAND?

They started making them in the USA also. So they are a little bit cheaper.

 

[Blackbrush]

The OP asked about flatter shooting......

 

[Notso]

Ok, let's talk terms of velocity spread. At a given distance of let's just say 1000 yards. And with your reloads you are getting the same consistency for both rounds of around 15fps ES. The faster moving bullet with the higher BC will be less affected vertically on target. Same with environmental conditions. If the DA changes throughout the day the slower moving .308 will be affected a little more. It's a percentage thing,if a you have a condition that causes a 2% shift in elevation to get on target that 2% equals a smaller number on the flatter caliber because it took less elevation to get there in the first place. All of the little things will affect a .308 worse than a flatter shooting caliber. Check it on a ballistic calculator at 1000 yds. Punch in your favorite .308 load at a given velocity then add 20 fps record the difference in inches at 1000. Then do it with a flatter shooting caliber and record the difference which will be less. Now, the difference between the two sums is how much more the.308's group would have grown vertically or how much further the hit would be from center or point of aim.

As you requested,wind drift left aside. As that is only one reason people score higher with flatter shooting calibers

Thanks. This is the only answer that addressed the actual question. For the others, I already stipulated that in wind and unknown range or range variations - a more efficient bullet in the real world is more desirable. I get all that, but none of those answers has to do with "flatter" except for Dimar1492's answer.

 

[Blackbrush]

Diver's answer did as well as my own.

Good luck.

 

[Pinecone]

Just ran some numbers in JBM.

.308 - 175 SMK at 2600 fps MV

.260 - 140 SMK at 2840 fps MV

The .308 drops an additional 29.2 inches from 1000 - 1025 yards. The .260 drops at additional 22.2 inches. So a 25 yard ranging error on a 4 foot round target at 1000 yards could mean a miss with 308 (5.2 inches below the lower edge) and a hit with 260 (1.8 inches from the edge).

 

[Notso]

Thanks everyone. Good stuff!

 

[Night Eagle]

I'll admit I have not shot a flatter round, I am a .308 guy but it seems to me...Apples to apples at 1k yards I expect to be ranging accurately or I should not take a shot. So dope is dope weather it is 8 mills from a 6mm projectile or 12 mills from a .308. Wind dope is same also...you still have to accurately read the wind and have to know your wind formula to be able to hit. So why is flatter better then I still don't get it

 

[Pinecone]

1) Flatter trajectory keeps the trajectory lower, so not in possibly different winds up hihger.

2) If you ranging is always 100% accurate, then you must never miss above or below a target.

3) Less wind drift means if you miss your wind call, you might still make the hit.

But if you are always perfect in your ranging and wind calls (including all the winds between you and the target that the trajectory passes), you will be fine. And you must be making EVERY hit and winning a lot of competitions.

 

[Night Eagle]

ok, correct me if im wrong, what im understanding is ...having a flatter shooting round is increasing your odds of hitting by a few extra % points, and i can see that in competition, when you need every iota of that extra percentage, its worth having...

honestly, ive only shot at known ranges, and really have never shot at unknown ranges, but i have a decent enough lrf, im ranging fairly accurately. and i dont compete in the kind of competitions you are thinking about. i do miss shots, especially in unsupported positions, but when i know range and wind with my .308, usually im on target. im trying to understand why i should move to a 6mm round and for competitions, i can see why you would want that.

 

[GlockBlock]

You can say "lets ignore wind" but in real life there is always wind which makes the flatter shooting rounds better.

 

[jbailey]

1) Flatter trajectory keeps the trajectory lower, so not in possibly different winds up hihger.

This is hugely important. Wind speeds increase exponentially as you go higher - a 3mph wind at ground level maybe 6mph at +10ft and 15mph at +15ft. There is actually an engineering formula for estimating this effect (known as "wind gradient"). So you want to keep that bullet as close to the ground as possible to reduce the impact of the wind gradient. Traditional ballistic modelling generally does not take this effect into account - it simply assumes a constant wind speed over the entire flight path. All else equal, a flatter bullet will spend less time up in the faster winds and as such, experience less wind drift. This will nearly always improve hit probability.

 

[Onewolf42]

You can say "lets ignore wind" but in real life there is always wind which makes the flatter shooting rounds better.

+1000

A flatter shooting bullet is less afflicted by the wind so a slight misjudgement in the wind (or wind shift) can result in a hit with a higher BC/FPS round versus a miss with a lower BC/slower round.

 

[zac_c]

The flatter shooting and better it is in the wind allows for more human error and still hitting the target

 

[Dacam]

Just imagine trying throwing a baseball from the pitchers mound to home plate. Throwing it as flat as possible should be relatively easy, but try throwing the ball as high as you can (say 40ft) in the
air while still trying to hit the target. Its really much harder to hit near home plate the higher you throw the projectile. Same holds true with a bullet with a lot of drop, you will elevate the muzzle to compensate for it. If its a flatter shooting round, you don't have to elevate it as much which increases your hit probability. Extreme example but you get the idea?

 

[darth_ritis]

At longer ranges, a "flatter" round will have a straighter angle of approach on target. Geometrically, this means the target is bigger. A steep angle of approach puts the target at an angle which makes the target smaller from the bullet's perspective.

 

[Graham]

Wind is the key to the answer.