Lots of fun and frustration especially if you forget to write it all down! At that distance, it retains 400 ft lbs of energy. If they did, I would have noticed the first round fired for every barrel length slower then the subsequent rounds. Doing the opposite is a bit more complicated. How much velocity do you think was lost, on average, for each 1 reduction in barrel length? By ammo type, the average FPS loss per inch was: 24.6 (Win 147 FMJ), 22.8 (IMI 150 FMJ), 20.9 (Fed GMM 168gr), and 22.5 (Win 180PP). The 7.6251 NATO chamber is imperceptibly longer than the .308 Winchester, extending between 0.006 and 0.010 inches beyond the .308 SAAMI specs. My calculations assume a 1.75 sight over bore height. NOTE: Many shooting newbies may see the number combination 7.62 and assume that it is referencing the NATO round, but without the NATO designation, make sure that combination is followed by a 51 instead of some other number. To make the test even more interesting, four different types of .308 Win factory ammunition were chronographed at each barrel length. He,he. Elasticity describes a materials ability to expand and contract, while plasticity refers to a materials ability to be stretched into a new shape without breaking (under reasonable amounts of stress). Test Barrel Lost 22.7 FPS Per Inch (.308 Win Chambering) Selecting the best barrel length for the .300 BLK can be a double-edged sword. Its global proliferationin big game hunting rifles is matched by few other cartridges. Gold Dot Short-bbl HP: Henry Big Boy 20" barrel: 1555: 1527: 1613 Registration on or use of this site constitutes acceptance of our Terms of Service. class bullets. mostly) paid for everything ourselves, and we did not receive any kind of sponsorship
brass or casing) is the shell of a firearms cartridge that houses the propellant. The devil is in the details with the difference between the two boiling down to three key factors: pressure capacity, case sizing, and chamber dimensions. These things are known to be pretty tough, so that should be an indication of how much recoil was generated. Much Different Results with 6mmBR and a Longer Barrel As an all around work horse for sniping that works great for both Law Enforcement and military sniping, the .308 is hard to beat. Are 7.62 NATO (a.k.a. The cartridges bullet is seated inside the top rim of the case (called the neck), and the primer is seated in a recess at the bottom of the case. Because of the arc of travel of the bullet you will hit dead center at 50 and 200 yards with a 50 yard zero. Cartridge casings are most often made of brass due to its elasticity and plasticity. The IMI Samson 150 grain FMJ is a 7.62x51mm NATO spec cartridge. .32 Winchester Special, .308 Winchester (7.62mm NATO), .38-55 Winchester, .243 Winchester, .300 Remington Short Action Ultra Magnum, .25-35 Winchester, 7.82mm (.308) Lazzeroni Patriot, .260 Remington, .307 Winchester, 6.17mm (.243) Lazzeroni Spitfire, .356 Winchester, 6.71mm (.264) Lazzeroni Phantom, .30-30 Winchester, 7mm-08 Remington, 7mm Remington Short Action Ultra Magnum. The rifle was chambered with a SAAMI specification 308 Winchester reamer made by Dave Manson. })(); To comment on a post, click Post Title or "Comment" Link. Copyright GunData.org 2015 | Koenig Media, LLC | Links | Sitemap | Advertise. MagnetoSpeed barrel mounted ballistic chronograph. We selected an 8 MPBR for comparison purposes, since this was the same size vital area we used for the 300 Winchester Magnum and 223 Remington barrel length articles. Youd think I was disappointed, however, there was a smile on my face. Brian Smyth Once the gases (mostly) escape, the casing shrinks again, although it does not quite return to its original shape and size. We stopped at 500 yards, but I had some legit 2.5 500 yard 5 shot groups. We also have a 223 and 7 rem mag up there. I am cutting up a barrel. The testers described their procedure as follows: Ballistic data was gathered using a Magnetospeed barrel mounted ballistic chronograph. 7.62 NATO (a.k.a., 7.62x51mm) and .308 Winchester are two very common rifle cartridges commonly used by U.S. service members and civilians. Bill Marr The 7.6251 NATO chamber is imperceptibly longer than the .308 Winchester, extending between 0.006 and 0.010 inches beyond the .308 SAAMI specs. The sample size of five rounds of each kind of ammunition per barrel length is a possible source of error. performance comparable to the proven .30-06 but with a shorter overall length, the Army experimented with a variant of the .300 Savage that is designated the T65, a good two years before the 7.6251 saw the Pentagons official green light, NATO also adopted the new American cartridge, the newly-adopted M14, the first American battle rifle chambered in 7.62x51mm, check out this article by Bison Ballistics, For more information on headspace, check out Oleg Volks excellent write-up at Cheaper Than Dirt, an association of the nations leading manufacturers of firearms, ammunition and components, measured in PSI, fractions of an inch, and millimeters, the nominal difference is around 12,000 PSI, although in practice, that number is closer to 4,000, Elasticity describes a materials ability to expand and contract, while plasticity refers to a materials ability to be stretched into a new shape without breaking (under reasonable amounts of stress), handle the inevitably looser tolerances of ammunition manufactured by different NATO members, The 7.6251 NATO chamber is imperceptibly longer than the .308 Winchester, extending between 0.006 and 0.010 inches beyond the .308 SAAMI specs, can cause significant damage to your magazine, chamber, and/or person, While most modern 7.6251-chambered firearms are specced to safely handle .308 cartridges, The U.S. Army lists the 7.62s effective range (and thus, the .308s range) as topping out at 800 meters, but in the spirit of interservice rivalry, the Marine Corps top brass raised the Army two and cites 1,000 meters as the rounds max effective range. _gaq.push(['_setDomainName', '.accurateshooter.com']);
This was an average decrease of 73.1 feet/second per inch of barrel length. I would have guessed 150-200 feet/second velocity loss between 24 and 16.5 barrel lengths. Skip to main content; Skip to secondary menu; Skip to primary sidebar; . I fired 30 rounds of IMI Samson 150 grain FMJ at 28 and 16.5 and recorded the results. Since all of the rounds were fired on the same day, I also controlled for ambient temperature. In the good old days of Precision Shooting magazine (how we miss you! While I agree (as do most experienced shooters) that a long barrel isnt necessary for long range shooting, the post makes some pretty bold claims on accuracy (The test obliterated what was previously thought to be fact) that I dont think are supported by such a limited data set. Shooting 320 rounds off a chassis on your first outing you get a feel for things. Barrel length, Barrel length and velocity, Cartridge Selection Each cartridge wasfired five times at each barrel length and its velocity and standard deviation recorded. 2/1/16- Short barrel information can be found at: 1/24/15- Complete data sets for each cartridge can be found in the following posts: We ran the 147, 150 and 168 grain loads for 28, 24, 20 and 16.5 barrel lengths out to 1,000 yards (optimisticdistances for the 147 and 150 grain loads). The chops tests ranged in barrel length from 18" down to 3". Note: I also fired a 30 shots of the IMI Samson 7.62mm 150 grain FMJ with the 28 and 16.5 lengths- Ill discuss why later. lb Muzzle Velocity ft/sec. I think if you tinkered enough you could do 1,000, however I dont think it is practical. Muzzle: 100 YDS: 200 YDS: Velocity (FPS) 3050: 2691: . Your choice. While the .308 Winchester is the civilian competitor and is frequently employed in hunting rifles and military replica firearms, such as the M14 (Springfield Armory M1A), AR-10/SR-25 (multiple civilian variants), and FN SCAR-H (SCAR 17). Contact the author here. According to multiple non-scientific studies, the average .308 case weighs in around 160 to 170 grains each, while 7.62 brass usually comes in at over 180 grains apiece. Does anyone have data on bullet drop vs barrel length? which was specifically designed for long-range target shooting. Temperature was 47 F.. Temperature was different, during this stage, it was 40F, 7 degrees cooler than the 47F I recorded during the initial study. The rifle used to record data from 26 to 16.5 inches (above). There are plenty of good sources of information on this topic. on each to just browse the charts, click on a given ammunition type listed in the header of each chart
By using the same barrel, I controlled for bore size, chamber, and headspace- all of which will impact velocity. Once data was gathered for each cartridge at a given barrel length, the rifle was cleared and the bolt was removed. ammunition and other supplies, he was the brilliant gunsmith who worked with us to make
The U.S. Army lists the 7.62s effective range (and thus, the .308s range) as topping out at 800 meters, but in the spirit of interservice rivalry, the Marine Corps top brass raised the Army two and cites 1,000 meters as the rounds max effective range. Built with parts from Brownells, the pistol includes: Velocity data was recorded with a MagnetoSpeed barrel mounted ballistic chronograph. The .327 Fed. The 7.62x51 NATO is a superior round to the .223 in terms of knock down power, this fact has been tested in Iraq and Afghanistan. for a graph of how that particular ammunition performed, or you can download the raw
The brand new, factory AI AICS magazine also flew apart as few times. Great test ! I think the value of this data is worth the time, effort and expense. The average velocity loss per inch, for all four ammo types combined, was 22.7 FPS. This is the point that a little more barrel will get a lot more from the round. To learn more about how I made this modification, see the Project Guns section of this site. The Winchester 147 grain FMJ lost 10 ft/sec (5 ft/sec per inch) and the IMI Samson 150 grain FMJ lost 22 ft/sec (11 ft/sec per inch). Contrary to the popular urban legend, 7.62 NATO casings do indeed have thicker walls than .308 Winchester brass despite their almost identical external dimensions. Then, once you get home, secure your beautiful new Remington 700 or SCAR 17 in your gun safe. In fact the .308 Winchester 165gr bullet is traveling faster at 1000 yards than the .223 or 7.62x39mm at just 500 yds. No guessing, no models, no arbitrary numbers. over what ammo or caliber or gun is "best." The results of those tests can be found on our blog. the cylinder gap. the firearms community. Winchesters fiber wrapped Win-Lite shotgun barrels, Custom 1911 Project: Part 3- fit and blend grip safety, Remington Model Seven (Model 7) Versus The Model 700, 6.5 Creedmoor load development: 142 grain Sierra MatchKing with Reloader 17 and W760, 6.5 Grendel loads in a Howa MINIACTION (6.5 Grendel load development), Rifleshooter.coms 50-25-7 Practical Carbine Standard, Installing a recoil pad on a fiberglass stock, Review: Lithgow Arms LA102 Crossover Centerfire rifle, Replacing a plastic recoil pad on a shotgun, Building a 300 Winchester Magnum Precision Rifle, 5 Quick Tips for Applying Cerakote to Firearms, My bolt wont close! Powder burn rates can also make a difference. var _gaq = _gaq || [];
The .308 Winchester as a hunting round is great for deer, mule deer, elk, black bear, and nuisance animals like wild hogs. Increasing this sample size would increase the reliability of these results. When you switch this out with a .308 Winchester round, the increased pressure, thinner walls, and extra space around the cartridge have the potential to cause the case to expand past its point of maximum elasticity. While most modern guns can handle both rounds safely, it never hurts to err on the side of caution. This could have some potentially expensive consequences. It was LOUD. That is actually not correct. Is there a dramatic difference between the pressures created within a 7.62 NATO case and a .308 Winchester case? We did all the work. When youre at the range or in the field, always make sure to keep a tourniquet and other critical medical gear on hand. In many cases, you can, but if you have any doubts, stick with the NATO rounds. UPDATE 12/30/14: I tapered the barrel and installed a brake.