Following up on their test of 5.56mm and .300 Winchester Magnum ammunition velocities through different barrel lengths, Rifleshooter.com has posted a velocity vs. barrel length examination of .308 Winchester. One of the most well-balanced and versatile .30 caliber rounds in history, the .308 Winchester proved surprisingly well suited to almost all barrel lengths tested, with Winchester 147gr ammunition ranging from almost 3,000 ft/s from a 28″ barrel to just under 2,700 ft/s from a 16.5″ barrel:

Ballistic data was gathered using a Magnetospeed barrel mounted ballistic chronograph.  At each barrel length, the rifle was fired from a front rest with rear bags, with five rounds of each type of ammunition.  Average velocity and standard deviation was logged for each round.  Note: I also fired a 30 shots of the IMI Samson 7.62mm 150 grain FMJ with the 28″ and 16.5″ lengths- I’ll discuss why later.  Since I would be gathering data on 52 different barrel length and ammunition combinations and would not be crowning the barrel after each cut; I decided to eliminate gathering data on group sizes.

Once data was gathered for each cartridge at a given barrel length, the rifle was cleared and the bolt was removed.  The barrel was cut off using a cold saw.  The test protocol was repeated for the next length.

Temperature was 47F.

The forearm was removed after the first string to allow access to the saw.  Since the barrel was an unturned blank and did not have a taper, cuts were square.

All shooting was done from a bench, with a Sinclair rest and rear bag.

Results

308 Winchester Barrel length in inches versus Muzzle velocity in feet-per-second (ft/sec)Rifleshooter.com
Barrel length	Winchester 147 FMJ	IMI Samson 7.62 150 FMJ	Federal 168 Gold Medal	Winchester 180 PP
28	2965	2823	2706	2632
27	2962	2800	2697	2607
26	2955	2801	2673	2597
25	2917	2769	2659	2585
24	2909	2766	2635	2553
23	2877	2744	2618	2553
22	2837	2718	2597	2527
21	2807	2683	2580	2507
20	2804	2679	2565	2478
19	2757	2634	2532	2441
18	2739	2595	2523	2411
17	2707	2577	2481	2401
16.5	2682	2561	2466	2373
AVG velocity loss fps/inch	24.6	22.8	20.9	22.5

The data presented as a line chart

 

 

These sorts of studies can really help readers understand their subjects better. Especially when methodology is recorded meticulously like this, not only are the data helpful for determining ballistics from a rifle of known barrel length, but also what barrel length is right for a certain purpose.

And just maybe, Rifleshooter’s 16.5″ barrel length results with 147gr ammunition have me taking a second look at that 16.25″ barreled DSA SA 58 at my local gun shop…

Be sure to follow the link and read the whole thing.