Ballistics Chart For 308

Understanding a Ballistics Chart For 308

A ballistics chart is just a table that tells you where your bullet lands at various distances based on the cartridge, bullet weight, muzzle velocity, and environmental conditions. For the .308 Winchester, these charts are everywhere because it is one of the most common hunting and precision rifle rounds. The data comes from applying the drag function to your projectile's ballistic coefficient over distance. Most charts you find online are generated by software like JBM Ballistics, Applied Ballistics, or QuickTarget, using standard atmosphere models. The raw numbers on a chart typically include drop in MOA or inches, wind drift, retained velocity, energy downrange, and time of flight. If you are shooting long distances with a .308, these figures matter a lot. At 600 yards and beyond, a .308 bullet drops significantly, drifts noticeably in crosswinds, and starts losing supersonic velocity depending on your load. That is why having accurate reference data is important.

Generating Your Own Ballistics Chart For 308

I stopped relying on generic charts years ago after spending way too much time guessing at 800 yards. The approach that works is straightforward. First, get your actual muzzle velocity through a chronograph. Factory boxed charts assume a standard barrel length of 24 inches, but if you have a shorter or longer barrel, your velocity changes enough to throw off holdovers. I run a LabRadar or Chrony and shoot three to five rounds to get an average and standard deviation. Then input your bullet's G1 or G7 ballistic coefficient, your zero distance, barrel length, ambient conditions, and a drag model into JBM or a similar program. The output gives you a personalized table that actually matches what your rifle is doing. The real work starts with calibrating that ballistic coefficient against real results. Manufacturers lie about BC almost constantly. Hodgdon, Sierra, and Berger sometimes get close, but Hornady's G1 BC for their SSTs has been shown to be roughly 0.015 to 0.025 higher than reality when measured against G7 drag models. A G7-based chart for .308 will always be more accurate at long range than a G1-based one. If you shoot beyond 800 yards, switch everything to G7. The difference becomes significant enough to cause missed shots on steel if you stick with G1 numbers. I keep a spreadsheet with my chronograph data, BC values for each bullet I use, and observed impacts versus predicted impacts. Over time the pattern tells you whether your BC is high or low and by how much. I then adjust the software input and re-run the chart. This process usually takes about an afternoon on the range and ends up saving you hours of trial and error later. It is not glamorous but it works consistently.

What the Numbers Actually Mean

Multiplying drop in MOA by your distance in hundreds of yards gives you approximate holdover. So if your chart says 3.8 MOA drop at 600 yards and your scope turrets are MIL-based, you convert using the 600-yard mil equivalent of about 1.08 MIL per MOA. That means roughly 4.1 MIL of elevation. If you do not convert properly, you end up shooting low and wondering why. Keep a quick reference card in your gear box so you are not calculating on the range under wind pressure. Wind drift is often the harder variable to estimate. A .308 bullet with a BC around 0.480 to 0.520 G7 will drift approximately 25 to 35 inches in a 10 mph full-value wind at 600 yards. At 800 yards, that drift jumps to roughly 45 to 65 inches for the same wind. The relationship is not linear. Wind speed estimates are where most people fail, not the math itself. A 5 mph miscalculation on wind can push your impact 10 to 15 inches off at 600 yards. Learning to read mirage and flag tape beats any wind meter at distance. Downrange energy matters less for human-sized targets past 600 yards because terminal performance is already guaranteed by the bullet design, but it becomes relevant if you are hunting medium to large game at extended ranges. A typical 168-grain MatchKing at 2800 fps muzzle velocity still has around 1200 to 1400 ft-lbs of energy at 800 yards, which is plenty for deer-sized animals but borderline for larger game depending on shot placement. If you are thinking about taking elk at 900 yards with a .308, you should really question that decision before you pull the trigger.

A Real Problem I Had With a .308 Chart

I was shooting a 175-grain Berger Hunter at a competition once and the chart was predicting solid hits at 700 yards in light wind. It did not work. I was consistently landing 4 to 6 inches low and slightly right. After a long evening of troubleshooting, I realized the issue was temperature. My chart was built using a standard 59-degree Fahrenheit atmosphere. That day the temperature was closer to 85 degrees with high humidity. The air density change alone shifted my point of impact by nearly 5 inches vertically. I recalibrated the chart using actual atmospheric density readings from a Kestrel and got it within an inch. That is an easy mistake to make and something most online calculators will not flag unless you enter real-time weather data. Another thing nobody tells you about .308 ballistics is barrel crown condition. A slightly damaged crown can add two to four inches of horizontal spread at 600 yards without you noticing until you are comparing grouped shots against a perfectly clean chart. Check your crown regularly. A worn or dented crown makes your ballistic data useless regardless of how good your software is.

Where Ballistics Charts Fail You

A chart cannot account for shooter error, so if your groups are consistently wide, no amount of chart refinement will fix that. Shooting from a rest is very different from shooting off-hand. Transitioning between the two without re-zeroing or adjusting your expectation of group size is a common mistake. The chart assumes a steady platform. It does not know you are standing on uneven ground with a heavy crosswind pushing you back. Atmospheric modeling is another limitation. Standard atmosphere calculations assume sea level pressure at 29.92 inches Hg and a standard lapse rate. If you are at altitude or dealing with a frontal system, those assumptions break down. A Kestrel weather meter with ballistics output gets you much closer than any generic chart. The cost of a decent Kestrel pays for itself the first time you use it at long range. Also worth noting: the .308 is a short-range precision cartridge in the hands of someone who expects 1000-yard performance. It can do it with the right bullet and high velocity, but it struggles with transonic instability past 900 to 1000 yards depending on your BC and muzzle velocity. Once the bullet transitions through the sound barrier, drag increases unpredictably and wind drift behaves differently. If you need reliable performance at 1000 yards, the .308 is not your best choice. The 6mm Creedmoor or .300 PRC handle that distance with less sensitivity to environmental variables and more consistent terminal performance.

Most .308 reloaders stop getting useful data past 800 yards anyway because velocity spread starts eating consistency. A standard deviation of 20 fps at the muzzle translates to roughly an inch of vertical spread at 800 yards. If your load is running 30 fps SD or higher, your chart becomes theoretical rather than practical. That is why reloading quality control matters more than any software you use.

Where to Find or Download a Ballistics Chart For 308

JBM Ballistics offers a free calculator at jbmballistics.com and exports detailed charts in PDF or CSV format. Applied Ballistics has a free iOS and Android app that generates charts directly from your rifle setup and saves them for field use. Hornady also provides a free ballistic calculator on their website with downloadable tables. There are no official government or military charts for the .308 that you can use freely, since the military does not publish ballistics data for public consumption. The commercial tools listed above are reliable and updated regularly. Avoid charts posted on random forums without any source attribution, since those often contain outdated or incorrect ballistic coefficients. I stick to JBM for desktop work and Applied Ballistics for the range because it syncs with my Kestrel and gives me real-time adjusted charts without having to go home and recompute anything.