The T65 was essentially a .30-06 with a shorter 51mm rather than 63mm case.
Two years later theU.S.
Army adopted the 7.6251 cartridgeand urged its acceptance by NATO, which complied in 1957.
Should you shoot .308 or 7.62 NATO in your rifle? Is there a difference?
National Match loads fueled by 41.7 grains IMR 4895 kicked 174-gr.
BTHP bullets to 2,548 fps.
Tracer, frangible, armor-piercing and grenade-launching loads followed.
The .308 arrived first, as a sporting cartridge, in 1952. The 7.62 NATO, same dimensions, came in ’57.
To hunters, infantry cartridges have all the cachet of beige filing cabinets.
Utility, like wisdom, can be an acquired taste.
A Second Look
But the .308 soon earned plaudits afield.
Early military brass was thicker and not as uniform as commercial. Neck turning can improve accuracy.
Commercial makers began to chamber bolt-action, lever-action, pump-action and autoloaders in the round.
It has roughly half the capacity of a .300 Weatherby Magnum.
Traditional loads sent 150-gr.
The .308 (left, shown with .270 and 6.5×55) is a true short-action cartridge.
Seth Swerzcek at Hornady tells me its top-selling .308 load is still the 150-gr.
SST, albeit Superformance ammo with 165-gr.
InterBonds at 2,840 fps brings more muscle.
This gelatin cavity shows terrific damage inflicted by a 150-gr. Hornady Superformance .308 load.
Bench Rest shooters embraced the .308.
With it, Dave Hall drilled a .4612 knot to win the Sporter class at the 1967 National Matches.
In 68, Ferris Pindell won with a .3594 group fromhis.308.
Popular in National Match competition, the .308 yields about 4½ inches to 10-mph wind at 600 yards.
Meanwhile, the round was proving itself in military circles internationally as the 7.6251 NATO.
Whats the Difference?
One of the biggest questions when comparing the 7.62 vs. 308 is whats the difference?
Black Hills Ammunition loads both commercial and military ammo. Here: gelatin test of a 175-gr. Tipped MatchKing bullet.
The cases are identical same 2.015 length, 20-degree shoulder, .473 rim.
Body and neck are the same.
Cartridges are loaded to the same 2.800 overall length.
Long bullets for long shots prompt sharper rifling twist, but 1-in-12 still works for almost all bullets.
Of course,loadscan differ.
We use the same brass and primers for commercial and service-contract ammo, says Swerzcek.
Typically, Hornady recommends loads for a contract.
Commercial loads for the .308 generally feature bullets of 110 to 185 grains. Handloaders have heavier options.
Officials approve or tweak specs.
We hew to them.
Standards of both rounds are governed by SAAMI and its European equivalent, CIP.
The M1A rifle (shown) from Springfield Armory is a semi-auto rifle inspired by the 7.62 NATO M14 rifle.
Maximum average breech pressures differ, with the.308 having the higher range.
Gunsmithing instructor Fred Zeglin notes different measuring methods can yield such disparities.
The first 7.6251 NATO pressures were retrieved by copper crusher.
Current piezo-electric reads on .308 ammo are more precise and repeatable, often higher.
Jeff Hoffman atBlack Hills Ammunitionnotes differences in measurement location.
Pressures for the 7.6251 NATO may be taken at the case mouth instead of mid-case.
We check production at both places, commonly seeing slightly lower values at the mouth.
A small difference, but important if youre loading thousands of rounds to exacting standards.
What about maximum horizontal range?
Its listed at 4,500 yards for the .308, and 5,500 for the 7.6251.
Different bullets in the trials, say ballisticians.At extreme range, ballistic coefficient rules.
SAAMI diagrams show a headspace measure of 1.630 to 1.640 for the .308.
Barrel-maker John Krieger tells me even his reamers with special-order throats hew to SAAMI headspace specs.
Freebore and leade angle are where .308 and 7.6251 NATO chambers seem to differ.
For .308s, JGS shows .900 freebore of .3100 diameter, with a 1-45 leade angle.
Chambers in 7.6251 NATO are cut with 1.355 of 3.095 freebore, a 5-40 leade angle.
Government diagrams confirm that steep leade.
A New Twist?
A common twist for both cartridges is the original 1-in-12.
For the leggy bullets popular now, faster spin is common.
Dave Tooleys Bench Rest experience nudges him toward modest spin rates.
Having chambered more than 7,000 barrels, he likes 1-in-12 twist even for long-range bullets.
An exceptional 1-in-14 Hart barrel held half-minute accuracy with flat-base 187s at 1,000 yards.
Hornady ballistician Scott Javins agrees with Tooley that targets tell the story.
But he understands shooters choosing sharper spin.
They heed caveats from bullet-makers, and gyroscopic stability values.
GS, he explains, responds dramatically to higher spin rates.
ELD Match at 2,546 fps from a .308 barrel with 1-in-1114 rifling spins at 162,960 rpm.
The same bullet sent at 2,528 fps from a 1-in-8 bore spins at 223,830 rpm.
He adds that GS disparities may not show up on targets or game at ordinary ranges.
Which Is Better: 7.62 or .308?
The .308, however, dominates ammo rosters, with 79 loads from five U.S. ammo makers.
Federal catalogs 24 loads, Hornady 17.
Even Norma of Sweden has seven loads, more than for any other cartridge in its line.
No centerfire round is chambered in more rifles worldwide.
Whats the Bottom Line?
The 7.62 NATO M1A can also safely fire both rounds.
you could also check this on your own with quality Go-NoGo headspace gauges.
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