Flattest trajectory!

[andym79]

Hi, I am looking to buy a new rifle for shooting at 200 and 300 yards, the shooting will be done as part of a field rifle competition (sitting and standing post_ and at a club level bench-rest. I appreciate it varies greatly depending on loads and projectiles used, but as a generall rule, which of these cartridges will shoot flatter or is it pretty much a moot point at at 300 yards?

.223 REM
.243 WIN
.270 WIN
.308 WIN
.30-06 SPFLD

 

[o Unforgiven o]

.243 loaded with light and fast 55 or so grain bullets will be the flattest. Followed in order by .270, .223, 30-06, and .308.

 

[redneck2]

or is it pretty much a moot point at at 300 yards?

Yep

Ask Mr Google to look up ballistics charts. That way, you can choose the particular bullet you are going to use. If it's for target, I'd use the .223 because of recoil, noise, barrel life, and cost of shooting.

 

[3gunaddict]

I read an article that really emphasized velocity for a flatter trajectory, so I would try to get the fastest velocity (with not too light of a bullet) you can out of the caliber you choose.

 

[dprice3844444]

223 would be best due to light recoil,follwed by 243. bolt gun or semi?

 

[redneck2]

I read an article that really emphasized velocity for a flatter trajectory, so I would try to get the fastest velocity (with not too light of a bullet) you can out of the caliber you choose

In my experience, guns are like cars. The faster they go, the touchier they get. There's a reason BR guys use rounds that have short, fat cases and moderate velocity. If I were to get a new rifle for target, it would be a 6BR. My son-in-law has one. Quite accurate

Unless I read something by someone that I REALLY trust, writers typically have little more qualification than most of us idjits on the internet. Being a writer is more about language skills than knowledge. FWIW...I used to write for one of the local rags.

In my youth, I used to live and die by Outdoor Life, Guns & Ammo, and Field & Stream . Then I met some of the writers. Wasn't so impressed after that.

In any event, accuracy seems to have more to do with the quality of the bullet, barrel, and load than what case the bullet is stuff into. Once those are top notch, tweaking comes into play.

YMMV

 

[rcmodel]

which of these cartridges will shoot flatter or is it pretty much a moot point at at 300 yards?

Moot point.

A higher trajectory is just a simple change in your sight setting when you go to the 100, 200, or 300 yard line. It is a never changing constant as long as you don't change loads.
So it matters not.

What matters on a windy day is how much wind drift you have to deal with.
Wind speed is much harder to judge and compensate for then known ranges.

Fast light bullets get blown off course far worse then heavier slower bullets with a better ballistics coefficient.

So, that is what I wold look at when choosing a caliber & load.

rc

 

[Ghost Tracker]

How "serious" are you planning to become about accuracy and financing this hobby? A big budget would suggest a check & see of what the world record holders are shooting. The more hobbyist angle would mean a "most fun for the funds" approach. Like a mechanic once told me "Speed costs money. Exactly how FAST do you wanna' go?".

 

[Strykervet]

Moot point.

A higher trajectory is just a simple change in your sight setting when you go to the 100, 200, or 300 yard line. It is a never changing constant as long as you don't change loads.
So it matters not.

What matters on a windy day is how much wind drift you have to deal with.
Wind speed is much harder to judge and compensate for then known ranges.

Fast light bullets get blown off course far worse then heavier slower bullets with a better ballistics coefficient.

So, that is what I wold look at when choosing a caliber & load.

rc

You are right and you are wrong. For the most part what you say is good stuff.

The trajectory isn't the problem, the flight time is. The higher the max ordinate, the longer the curve, the longer the flight time, thus the longer wind, your greatest variable, has to act. Same with velocity, it increases or reduces flight time.

How important is all this? About as important as selecting a high BC bullet that scoots.

Simply put, the faster and straighter you can get there the better for accuracy. It is all about reducing or eliminating variables, and focusing on the important ones first. If wind is important, then so is flight time since the wind variable is dependent on that.

6.5 I THINK has the best BC for these size bullets. Gotta go Lapmag to get any better. I use it in 6.5G, and that rifle is sub-MOA, just spectacular, but the 100gr bullets have worked better for me than the 123's --could be due to velocity being more important than BC at these loadings. Accuracy, it is all about eliminating the most important variables first. It is like using a laser beam at 300m and less.

For the loads you picked, I'd go ahead and throw .260 and 6.5 Creedmore and Lapua in there too. Not sure how much the shorter cartridge has to do with accuracy to be honest, but I can sure say that Grendel is amazing.

 

[rcmodel]

You are right and you are wrong.

Maybe? Maybe not?

Here is just one example.
22-250 Rem cartridge
45 grain bullet at 4,000 MV.
60 grain bullet at 3,500 MV.

500 yard velocity:
45 = 1,440 FPS
60 = 1,607 FPS

500 yard drop:
45 = 57".
60 = 61".

500 yard time of flight:
45 = .634 Sec.
60 = .637 Sec.

20 MPH cross-wind drift:
45 = 91" drift.
60 = 73" drift.

You be the judge which one would be easier to hit with at 500 yards when the wind is blowing!

rc

 

[o Unforgiven o]

I must have missed something in the OP, but all I can see is he wanted to know which one would shoot the flattest. I remember seeing nothing about drift, cost or other calibers, just flat shooting.

.243 loaded with light and fast 55 or so grain bullets will be the flattest. Followed in order by .270, 30-06, .223 and .308.

This is a screen shot from the Winchester ballistics app, each round has the same bullet in the lightest weight. Flat shooting.

 

[andym79]

I did not ask about drift, but the responses have been good, just because a cross wind of more than 5mph is very range at the range I go to doesn't mean drift should be discounted!

With this fancy software can you tell me roughly what drop and drift would be at 300 yards for a 165gr projectile with a MV of 1800 fps?

Thanks

 

[AABEN]

You might look at the 25.06 It is a very good round It is a 30.06 neck down

 

[o Unforgiven o]

I did not ask about drift, but the responses have been good, just because a cross wind of more than 5mph is very range at the range I go to doesn't mean drift should be discounted!

With this fancy software can you tell me roughly what drop and drift would be at 300 yards for a 165gr projectile with a MV of 1800 fps?

Thanks

Sure. With a wind of 8 mph, 1800 fps, 165gr, .400 Ballistic Coefficient, with a sight in at 100 yards with a max range of 300 yards;

Drop= 40.59 in.
Drift= 11.76 in.
Time of Flight= .59 sec
Velocity at target= 1337 fps
Energy at target= 651 ft/lbs.

 

[Zak Smith]

rcmodel is more correct.

_Bullet_           _BC_ _MV_         0     250     500     750    1000    1250 | YARDS
A                 0.640 2850 >    2850    2510    2196    1907    1642    1413 | velocity (fps)
B                 0.540 2950 >    2950    2541    2169    1831    1532    1286 | velocity (fps)
C                 0.508 3400 >    3400    2924    2493    2103    1752    1449 | velocity (fps)
D same time A     0.508 3130 >    3130    2681    2273    1905    1577    1308 | velocity (fps)

A                 0.640 2850 >    0.00    0.28    0.60    0.97    1.39    1.88 | time (sec)
B                 0.540 2950 >    0.00    0.27    0.59    0.97    1.42    1.95 | time (sec)
C                 0.508 3400 >    0.00    0.24    0.52    0.84    1.23    1.71 | time (sec)
D same time A     0.508 3130 >    0.00    0.26    0.56    0.92    1.36    1.88 | time (sec)

A                 0.640 2850 >    0.00    3.04   12.96   31.16   59.48   99.95 | wind (inches)
B                 0.540 2950 >    0.00    3.47   14.96   36.46   70.63  120.17 | wind (inches)
C                 0.508 3400 >    0.00    3.06   13.14   31.97   61.93  106.10 | wind (inches)
D same time A     0.508 3130 >    0.00    3.40   14.71   36.00   70.06  120.03 | wind (inches)

A, B, and C represent a spectrum of loads for a particular .30 caliber cartridge. A has the highest BC but the slowest initial velocity. C has the highest initial velocity but the lowest BC. "A" obviously has the best wind drift and would be my choice for long-range shooting.

Load D is the low-BC bullet from C slowed down to provide the same flight time as load "A". Clearly its wind drift is worse than load A.

Wind drift is a function of both time of flight and BC.

 

[Hummer70]

Based on your original question and if I understand it right you are looking for a round that you can use the same zero with at 200 AND 300 yards?

As several have pointed out wind can give you lots of problems. Not so much at 100 yards but at 200 on out mother nature is your enemy along with gravity and your own body can let you down if you don't use the proper technique.

For instance I was shooting a 6.5X06 with 142 grain Sierra MKs chronographing 3015 fps a couple weeks back at 200 yards. I was getting a SD of 8 to boot.

The wind that day was constant about 15MPH and gusting and letting off constantly. I was shooting iron sights at a 600 yard target reduced for 200 yards. 20 shot group measured 1 7/8" high and 2 11/16" wide for a 200-13X target. Wind was from 4:30 and you will probably find tail winds can really play havoc with you.

If you can't read the wind and you have wind you are very likely to get taken out by the weather rather than gravity.

The flatest shooting long range now than can be fired from the shoulder sling supported would most likely be the 6.5MM bullets. They have won everything at Camp Perry at 1000 yards for about 12 years now and most are running 2975 - 3000 fps as that seems to be the sweet spot for those bullets. The 300 Win Mag still holds the record at 200-19Xs though but they no longer win.

There are trade offs for such performance, first is the 6.5MM high velocity barrels have a useful barrel life of about 800 rounds which for most folks is about three to five years of 1000 yard competition. 300 Magnums on the other hand have a barrel life of about 500 rounds.

There is work being done now by a firm to increase barrel life with a process they are using they are using identical barrels with identical charges fired at the same rate of fire and the untreated barrel has developed fissures in the throat along with erosion at the 300 round point. I am shooting a treated barrel and I have 475 rounds on mine with very little erosion and min movement of erosion gage but my rate of fire includes rapid fire strings.

The Army Marksmanship Unit has some fabulous shooters and the ARs they build are also outstanding and they use the 77 and 80 grain Sierra bullets. There is a segment on the history channel I saw awhile back and it was revealed they change barrels every 700 rounds.

A lot of shooters find on their ARs that they use the same zero at 200 and 300 yard rapid fire as with certain loads and the ARs have a high sight line and the bullet passes through the sight line at 200 as it is rising and passes back through the sight line at 300 on the back side of the trajectory arc.

Rule of thumb heavy bullets + slow propellant = shorter barrel life.

You can play with different velocities and be pretty close with scoped hunting rifles but to make your selection based on velocity only may well not be beneficial to your goals.

Warning: loading a round to max velocity is not generally the answer and backing off max loads will often times give you a much smaller group. For instance I laid in a bunch of 30.06 Match ammo when the DCM released it 30 years ago. I found that by pulling the bullets, dumping the powder (which is 4895 and 47 grains) and reweighing the powder down to 43.3 grains I could reduce the group size dramatically. This also has an benefit of longer barrel life so it is a win win.

 

[AABEN]

The hotter and faster shorter the life of the barrel. You said it in the last part of your post less powder the slower the barrel well last longer.

 

[The Lone Haranguer]

I wish to learn. If the maximum distance is a fixed 300 yards and the other ranges are known and fixed, does this really matter?

 

[rcmodel]

No.
That's what I said in post #7.

All that matters with fixed distance targets is you know the elevation setting for each range, and how to adjust for the wind.

300 yards isn't far enough for velocity or trajectory to make one little bit of differance between the 5 calibers the OP ask about.

rc

 

[beatledog7]

Wind drift is a function of both time of flight and BC.

Given that undeniable logic, is there any way to determine a sort of break-over point? That is, at what point does a heavier, slower bullet with a high BC get blown off course more than a faster, lower BC bullet that is affected more per unit of time by the wind but has the advantage of being affected for less time due to its higher velocity?

What's the key factor? BC, time of flight, or wind speed?

Not looking for specific figures, just a rough order of magnitude.

 

[rcmodel]

You could determine it using trajectory tables in some reloading manuals.

Or ballistic software Like Remington SHoot that is available free from them.

I think in general though, off the top of my head?
In any given caliber, you will always find the heavier bullet with the higher BC to drift less at whatever velocitys the cartridge is capable off with light & heavy bullets.

rc

 

[Zak Smith]

That is, at what point does a heavier, slower bullet with a high BC get blown off course more than a faster ...

At the point at which it does. Run the numbers in a ballistics calculator to compare your cases. JBM online is a good one.

What's the key factor? BC, time of flight, or wind speed?

It is a function of the first two. Wind speed is held constant to compare if load A or load B has more or less wind drift in the same wind. If you can't use a computer to do the experiment, choosing the higher BC bullet is usually the safest bet, but keep an eye on the drop rates.

 

[beatledog7]

Guess I'm going to be downloading some software. Thanks!

 

[redneck2]

Guess I'm going to be downloading some software. Thanks!

Nah. Go to the 6BR website. There are all kinds of calculators there. Free.
Or, this is the one Zak suggested. You can just play to your heart's content
http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

 

[Jasper1573]

Wow, this is one of the best discussions I have seen on here in a while. So, here is my input:

.223 REM........great gun out to 600 meters, but light bullet weight is subject to wind
past 300 meters
.243 WIN.......shoots well, and inexpensive to shoot...accurate...my 17 year old
daughter shoots a Rem 700 SPS Varmint in competition and shoots 2 MOA
at 300 yds on 20 round group; light recoil
.270 WIN.......really flat trajectory...no issues at all at 300 yds...my Dad has a HOWA and
it shoots great, but kicks the fire out of you
.308 WIN.......great all-around choice...shoots anything from 110 grain up to 200 grain
bullets; very accurate and a good choice from 100 yds out to how far can
you see; not as flat shooting as .270 but less recoil and more versatile
.30-06 SPFLD..proven weapon capable of .308 performance and better, but recoil is more;
costs more to shoot and provides no better accuracy than any other caliber

Other 6mm and 6.5mm calibers are super target rifles, but generally costs a good bit more to purchase one worth having, and are likely better at punching paper than anything else. If that's all you want to do, then they are great. If you wish to hunt, then I would stick with one of your original calibers.

Given that undeniable logic, is there any way to determine a sort of break-over point? That is, at what point does a heavier, slower bullet with a high BC get blown off course more than a faster, lower BC bullet that is affected more per unit of time by the wind but has the advantage of being affected for less time due to its higher velocity?

I don't have a definitive, scientific answer to the above question; however, I will give you an example from my high school football days. There was this fellow up in TN from Lake County...he was about 300 pounds. I don't quite know his BC, but his sectional density was high, and once he got up a head of steam, it didn't matter who ran into him or at what angle or velocity, he didn't veer off his course much until he got where he intended to go. It is the same with heavier bullets. If you do the ballistics on a .308 Win at varying weights and velocities, you will find that the smaller bullets are touchy as stated in a previous post, and the really heavy bullets tend to be a bit on the slow side and drop too much. But like most things in life, if you pick something in the middle, you will find that it performs much better than either extreme. That is where the .308 falls out, somewhere in the middle, and in the middle of the .308 spectrum, something in the 155-180 grain range seems to perform best between 300 yds and 1000 yds. For 300 yds, I have found the 165-168 grn bullets do well, and past that I prefer the 175 grn.

Whatever you choose, they will all get the job done. Each caliber has it own advantages and disadvantages.

If you want to do some ballistic analysis for free, use this on line software. I have found it to be accurate.

http://www.biggameinfo.com/BalCalc.aspx