function calculateRateOfTwist() {
var barrelLength = parseFloat(document.getElementById("barrelLength").value);
var bulletDiameter = parseFloat(document.getElementById("bulletDiameter").value);
var twistRatioInput = document.getElementById("twistRatio").value;
var resultsDiv = document.getElementById("rateOfTwistResult");
var explanationDiv = document.getElementById("explanation");
resultsDiv.innerHTML = "";
explanationDiv.innerHTML = "";
if (isNaN(barrelLength) || barrelLength <= 0) {
resultsDiv.innerHTML = "Please enter a valid positive barrel length.";
return;
}
if (isNaN(bulletDiameter) || bulletDiameter <= 0) {
resultsDiv.innerHTML = "Please enter a valid positive bullet diameter.";
return;
}
var twistRatioParts = twistRatioInput.split(':');
if (twistRatioParts.length !== 2) {
resultsDiv.innerHTML = "Invalid twist ratio format. Please use the format '1:X', where X is the number of inches per full turn.";
return;
}
var inchesPerTurn = parseFloat(twistRatioParts[1]);
if (isNaN(inchesPerTurn) || inchesPerTurn <= 0) {
resultsDiv.innerHTML = "Please enter a valid positive number for inches per turn in the twist ratio.";
return;
}
// Calculation: Rate of Twist is typically expressed as inches per turn.
// The calculator uses the input twist ratio directly, as it's the standard way to define it.
// If a different metric were needed (e.g., degrees per inch), further calculations would be here.
var rateOfTwist = inchesPerTurn; // Directly use the inches per turn from the input ratio
resultsDiv.innerHTML = "
Rate of Twist: 1 in " + rateOfTwist.toFixed(2) + " inches";
var explanationContent = "
What is Rate of Twist?
" +
"The
rate of twist, often expressed as a ratio like 1:10, describes how quickly a barrel's rifling makes one full rotation. In a 1:10 twist barrel, the rifling completes one full turn over a distance of 10 inches." +
"The rate of twist is critical for stabilizing bullets. Faster twists (lower numbers, e.g., 1:7) are generally needed to stabilize longer, heavier bullets, while slower twists (higher numbers, e.g., 1:12) are suitable for shorter, lighter bullets. Factors like bullet construction, velocity, and intended range also influence the optimal rate of twist." +
"
Barrel Length: The physical length of the barrel, measured in inches. This affects muzzle velocity and stability over distance." +
"
Bullet Diameter: The nominal diameter of the projectile, measured in inches. Different calibers have different standard bullet diameters." +
"
Twist Ratio: The specified rate at which the rifling rotates within the barrel. For example, a 1:10 ratio means the rifling makes one complete revolution every 10 inches of barrel length.";
explanationDiv.innerHTML = explanationContent;
}
.calculator-container {
font-family: sans-serif;
border: 1px solid #ccc;
padding: 20px;
border-radius: 8px;
max-width: 600px;
margin: 20px auto;
background-color: #f9f9f9;
}
.calculator-inputs h2, .calculator-results h3 {
text-align: center;
color: #333;
margin-bottom: 20px;
}
.input-group {
margin-bottom: 15px;
}
.input-group label {
display: block;
margin-bottom: 5px;
font-weight: bold;
color: #555;
}
.input-group input[type="number"],
.input-group input[type="text"] {
width: calc(100% – 12px);
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
}
.calculator-inputs button {
display: block;
width: 100%;
padding: 12px 20px;
background-color: #4CAF50;
color: white;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 16px;
transition: background-color 0.3s ease;
}
.calculator-inputs button:hover {
background-color: #45a049;
}
#results {
margin-top: 30px;
padding-top: 20px;
border-top: 1px solid #eee;
}
#rateOfTwistResult p {
font-size: 1.1em;
color: #333;
margin-bottom: 10px;
}
#explanation {
margin-top: 20px;
font-size: 0.95em;
line-height: 1.6;
color: #444;
}
#explanation h3 {
margin-top: 0;
text-align: left;
color: #333;
}