Long range shooting query

P

Pond James Pond

New member
I have a question about the logic of bullet choice.

Let's take .308 as an example. I personally load 155gr bullets. They can reach about 2890fps, even though my loads make less. So, they will cover a given distance in the time that passes before they fall to ground.

However, I've often seen it suggested when discussing shooting at long distances that a shooter should opt for 167gr or 175gr bullet for those 1000yd shots.

Surely a heavier bullet will have a lower velocity at the muzzle and so will travel a shorter distance before it falls to earth, so what makes it a better choice?
 
HA! I'm about 6,553 people down the list who is qualified to answer this, HOWEVER, I am the first one on the scene! :eek::D:p

It's about momentum. While the lighter slug has more velocity at the muzzle, it also loses velocity at a faster rate. For some large variances in bullet weight, it gets to be significant. So if you can find some ballistic tables that show you the down range velocity when comparing bullets on the light end versus slugs on the heavy end, you'll see why they heavy bullets win out.

And I'm sure there is far, far more to the equation than simply that, but again...

I was first to respond! ;):p
 
167 is a poor choice for 1000 yard shooting. The 155 Palma Hybreds and 175 match would be your best bet. 167 will start to tumble at around 800 yards for some reason. The 175 will buck the wind better,but as you say the 155 can be shot faster. I shot the 155 Palma Hybreds in matches,but went back to the 175's later on. Keeping a 175 SS to 1000 yards is very easy,so it is not a matter of falling to the ground.
 
Most bullets remain stable in flight as long as they are traveling faster than the speed of sound. Once they slow down below that point they become very unstable and inaccurate.

While the lighter bullets start faster, heavier bullets within the same caliber are longer. And much more aerodynamic. They will maintain their speeds at longer range.

At 100 yards the 155 gr bullet is moving faster, 2466 in my load. 190 gr bullets are only 2363 fps. But at 400 yards the 190's are 1672 fps while the 155's are down to 1539. As range increases the difference only gets larger.

The lighter bullet will always shoot flatter. Even though the heavier bullet is faster beyond 200-300 yards, it will never make up the speed the lighter bullet had at the beginning.

The difference is that the lighter bullet will become too slow to remain stable at some point. The heavier bullet may drop more, but will remain accurate at longer ranges. You can always adjust the sights for a little more bullet drop.

As long as you are not shooting at ranges where the lighter bullet is unstable then it doesn't really matter.
 
"Falling to earth" is not a factor at a mere 1000 yards.
The old .30-06 173 grain M1 bullet would travel up to 5500 yards.
You just twist the little knob on top of your scope so that the bullet hits the target at the range of interest.

The various 155 grain match bullets were designed for International Palma competition, for which the maximum bullet weight is 156 grains. (Berger even offers a 155.5 gr Fullbore Match bullet.) A long sharp nose and a boattail base give them a high enough ballistic coefficient for Long Range shooting, WHEN FIRED WITH HIGH MUZZLE VELOCITY. Like 3000 fps, which requires maximum loads in a long barrel.

Where bullet weight is not limited, the tendency is to heavier bullets, often MUCH heavier bullets. A friend attended the US National Championships for Long Range (1000 yards) F Class. He was shooting 185 grain .308 bullets and found that he was somewhat behind the curve, the winners were shooting 195 to 230. With considerable overloads, there was one chap whose brass life was 1.
 
So alongside my 155gr load, I could start looking at combining some N140 with a 175gr bullet and see if I can get a relatively quick, accurate load with that. With the Scenar bullet data suggests 2635fps from a test barrel that is 24" to my 26". So perhaps anything up to 2680...

My next concern is whether or not my .308 "Varmint" rifle will like a longer bullet. Its twist is 1:12. I seem to recall that faster twists suit smaller bullets...

1:12 still OK with 175gr?
 
Not all heavy bullets are the same either. You have to consider the bullets ballistic coefficient (BC). The higher the number, the better the aerodynamics. I have some Speer 150 gr bullets with a BC of only .295. Just for perspective.

Hornady SST's/150 .415
Barnes TTSX/150 .420
Berger/155 .439
Nosler/165 BT .475
Nosler/168 BT .490
Nosler/180 BT .507
Nosler/190 LRAB .640
Nosler/210 LRAB .730


A Nosler 220 gr Partition is heavier, but not designed as a long range bullet with a BC of only .351
 
Pond said:
I have a question about the logic of bullet choice.



Let's take .308 as an example. I personally load 155gr bullets. They can reach about 2890fps, even though my loads make less. So, they will cover a given distance in the time that passes before they fall to ground.



However, I've often seen it suggested when discussing shooting at long distances that a shooter should opt for 167gr or 175gr bullet for those 1000yd shots.



Surely a heavier bullet will have a lower velocity at the muzzle and so will travel a shorter distance before it falls to earth, so what makes it a better choice?
Click to expand...


I have a custom built .308 in a Bighorn Long Action. Reason for the long action was so that I could run 208 AMAXs or 210 VLDs.

Like has been mentioned, the ballistic coefficient is the ticket to long range hunting/shooting. The AMAXs I'm currently running are coming out of the 26" tube at around 2575 fps behind a dose of RL17. At the muzzle that equates to about 2900 pounds of energy and at 1000 yards it's around 900 pounds. This round with a .630 BC will stay supersonics to 1400 yards. On top of that in comparison to a 168g BTHP launched at 2700 fps, it will experience
about 30" less wind drift at 1000 yards in a 10mph crosswind.


I just dropped a deer in Nebraska with this load last week at 350 yards with no issues. I'm every confident in this rig out to much further than that as it has sufficient power to deliver devastating energy due to the high BC and heavy bullet.

I will probably switch to the 208g bullet for the steel sniper matches I shoot as well next summer to help reduce wind drift.

Overall I love the .308 caliber, very mild mannered and easy to load for.
 
What makes it a better choice?

Ballistic coefficient.


You can load a .270 Winchester with an 85 grain bullet to almost 4000FPS. Why isn't that a good long range choice? Because an 85 grain .277 cal bullet has a fairly low BC compared to a 150 grain boat tailed bullet. By 1000 yards, it will be moving slower than a 150 grain VLD launched at a significantly slower velocity. It will have more wind drift, and may have more drop at that point, as well.


Lower BC bullets tend to get effected by wind more, as well as lose their velocity much faster.

That's why you can't shoot shotgun pellets to 1000 yards, even if you ramp up the velocity.

Also, as speed increases, wind resistance grows EXPONENTIALLY. Faster bullets loose their speed faster given an equal BC.

Take .338 whisper vs .338 lapua

Launch a 300 grain VLD at 1050FPS and it may only lose 100-200FPS by 500 yards. That same bullet fired at 3000FPS from a .338Lapua may lose that velocity within 100 or even 50 yards. The lapua is obviously still moving faster, but it's also losing it's velocity faster due to wind resistance.

Shooting long range is more than just about drop. Bullet drop can be easily compensated for. One of the longest sniper kills was with a .50-90 sharps at over 1500Yards back in the 1800's. I worked it out in another thread, and it essentially ended up being comparable to shooting a 7.62x39 (AK47/SKS round) to 1500 yards. :eek:
 
People on the USN and USAF Rifle Teams have shot 190-gr. Sierra HPMK's from 24" 1:12 twist Garand barrels from 7.62 NATO cases. They left at about 2550 fps and stayed supersonic through 1000 yards. That was the most accurate long range load ever used in them. Lapua D46 185-gr. rebated base boattails were also used in these rifles from the same cases with the same powder charge of 44 grains of IMR4320 at about the same speed and also shot as accurate.

240- and 250-gr. Sierra HPMK's from 28: 1:8 twist .308 Win. barrels with IMR4350 leaving about 2175 and 2150 fps were also very accurate at 1000 yards. Yes, those very long bullets needed a long throat in the barrel. Fired only single shot in long range matches, that was OK.

The favorite load of the US Army Rifle Teams with their M14NM's was the M118 match round having its 172-gr. FMJBT bullet replaced with Sierra's original 180-gr. HPMK bullet with the 9 degree boattail bullet. Leaving at about 2600 fps from the 22" barrel with a 1:12 twist, they won a lot of matches and set some records, too. A 1:11 twist barrel did better in cooler weather. Some of their custom barrels were 1:10 twist When Sierra changed that bullet's boattail to a shorter 13 degree one identical to their 168-gr. HPMK bullet, they often went subsonic at about 900 yards and accuracy at 1000 dropped. The Army made contracts with Sierra to use their old tailing die forming those bullets and make their boattail the original long one with the 9 degree angle.

Good reading on long range ammo for the .308 Win. and 7.62 NATO round in several links in the following web site. Look through it for what interests you:

http://riflemansjournal.blogspot.com/p/articles-index.html
 
Well, I've found a .498 BC 170gr Lapua Lockbase bullet.

I'm hoping to try that over some N140. It is supposed to be a better than N135 and is dead close to varget in burn-rate.

I hope that my gun likes them as they are not cheap to buy!!

There was also another AMX (178gr), but that had a slightly lower BC and the extra 8gr would perhaps nudge recoil up.
I can cope with recoil, I won't deny that if stouter, I am more likely to flinch.
 
All I was going to add has been said but cliff notes in a single post:

1. When long range is the name of the game you should be shooting the heaviest bullet in your caliber that your rifle will feed reliably.

2. What it's really all about is ballistic coefficient or BC as your see it shortened to. The higher the number the better. I believe 1.0 would be "perfect", meaning the bullet doesn't lose speed or drop as it travels. This is not possible on the planet earth.

3. The faster a bullet leaves the muzzle the quicker it's velocity will diminish. However starting at a higher number does mean as it is losing velocity it will still be higher overall *to a point*. You might be able to push a lighter bullet faster at the muzzle but if you graph the velocity of that bullet with a heavier slower bullet (same caliber at max loads for apples:apples comparison) over distance the lines representing velocity will cross.

4. Wind has a harder time blowing an entire newspaper across a wind whipped alleyway than a single page of the newspaper. Same deal with bullet weight, the heavier bullet traveling in the same conditions as a lighter one will move less. Velocity comes into play here too. The faster the projectile is moving the less affected by wind it will be.

5. Sectional Density and bullet shape will have an effect as well. A more streamlined bullet will "buck the wind" better. Drive a Jeep Wrangler on a windy day, then drive an Acura integra or RSX. Similar weights but the Jeep has the aerodynamics of a brick.
 
1. There are some .50 bullets with BC over 1.0, because they are very heavy and the usual G1 BC is based on a different shape.

5. Sectional density and form factor are included in the computation of ballistic coefficient. A good form factor will to some extent make up for a low sectional density, as seen in the 155 gr Palma bullets. A high sectional density will to some extent make up for a low form factor, Grandpa was shooting his Krag at Long Range with 220 gr roundnose.
 
The problem with a "cliff notes" version is that
1. When long range is the name of the game you should be shooting the heaviest bullet in your caliber that your rifle will feed reliably.
Click to expand...

Actually the general wisdom is to shoot the highest BC bullet the fastest you can. The general wisdom falls down when you start talking about the highest BC bullets not being the most accurate (ie repeatable) in a particular rifle. The original Berger VLDs were notorious for this, mainly due to the secant ogive making seating depth more critical than the tangent ogive traditional match bullets use. Match shooters can cope with the wind, they can't cope with inconsistency.

2. What it's really all about is ballistic coefficient or BC as your see it shortened to. The higher the number the better. I believe 1.0 would be "perfect", meaning the bullet doesn't lose speed or drop as it travels. This is not possible on the planet earth.
Click to expand...

BC is rated against a reference projectile. The G1 projectile was a flat based spitzer bullet designed by Krupp way back in the 1800s. A BC of 1.0 would fly exactly like the reference model. A BC of higher than 1.0 would fly with less resistance than the reference model.

3. The faster a bullet leaves the muzzle the quicker it's velocity will diminish. However starting at a higher number does mean as it is losing velocity it will still be higher overall *to a point*. You might be able to push a lighter bullet faster at the muzzle but if you graph the velocity of that bullet with a heavier slower bullet (same caliber at max loads for apples:apples comparison) over distance the lines representing velocity will cross.
Click to expand...

This is wrong. Decreasing velocity in the supersonic range actually gets faster the closer you get to the transonic region because of wave drag. If you start out below the transonic region, this is mostly true (but not always because projectile shape still comes into play) and definetly not true for high BC match bullets launched over mach 2. The increasing wave drag in the transonic region is the major reason some projectiles like the 168 SMK are known to destabilize. The milspec 50BMG ball and even the 408 Cheytac rounds destabilize in the transonic region, they just don't hit the transonic region until around 1,400 meters.

4. Wind has a harder time blowing an entire newspaper across a wind whipped alleyway than a single page of the newspaper. Same deal with bullet weight, the heavier bullet traveling in the same conditions as a lighter one will move less. Velocity comes into play here too. The faster the projectile is moving the less affected by wind it will be.
Click to expand...

Wind does not push a bullet. Wind changes the net drag function on the bullet. A newspaper sheet is not spin stabilized, a bullet is.
5. Sectional Density and bullet shape will have an effect as well. A more streamlined bullet will "buck the wind" better. Drive a Jeep Wrangler on a windy day, then drive an Acura integra or RSX. Similar weights but the Jeep has the aerodynamics of a brick.
Click to expand...

Sectional density is less important than bullet shape. A high sectional density 160gr round nose 6.5mm bullet is going to have a lot more wind drift than a 140gr 6.5mm BTHP. For match bullets sectional density is not even a real consideration as it doesn't take much SD to punch a hole in a paper target. SD is much better used as an indicator for how efficiently a bullet will poke holes in tissue.


Jimro
 
It isn't all about BC.
As Jimro stated, if your barrel harmonics won't shoot it accurately it's advantage is nullified.
Loads developed for accuracy must also bear heavy consideration to velocity consistency. It might print a cloverleaf at 100 yards- but if you've got a MV variance of 50 fps, it's advantage is nullified.

Heavy, high-BC bullets are great. But it's usually not as simple as "I'm just going to use the highest BC bullet I can get my hands on".

My 7-08 will put five of the 150 SMK into one hole at 100. The 162 Amax- less accurate. Does the higher BC of .625 outweigh being slightly less accurate?

Depends...
 
Wind does push bullets sideways to the line of fire. For a given cross wind speed, a given bullet drifts sideways at the same speed for its entire flight. The small increase in the bullet axis angle to the LOF/LOS the further downrange it gets is insignificant.

As a bullet gets closer to the target, it's downrange velocity is slower; high BC bullets slow down less. For each 1/10th second time of flight, the bullet moves sideways the same amount. The closer it is to the target, the less downrange it moves.
 
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Well, every loading page that makes accuracy comments have said that N140 gives good accuracy in .308 so I'm tempted to try that next.

Bullets are a trickier choice. As usual it is hard to know where my shooting "skill" starts and a handload's inherent inaccuracy begins! :rolleyes:

So while my OCW tests with a 155gr Amax gave promising results that Unclenick helped interpret, another OCW test using the 155gr Lapua Scenar was far less encouraging. In fact it was completely inconclusive to my eyes...

I may try again there to see if results improve, but I'm left thinking that perhaps a 178gr Amax might be a better choice, than another Lapua in the 170gr Lockbase. And then I again remind myself that what my rifle likes is not as easily answered as a brand or bullet line name: the 155gr Amax may be good, but the 178gr bad. Or it may be even better of the Lockbase may trounce the lot and give me one-hole groups at 5 miles!!

Who knows...
 
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