30-06 vs 308 as observed by Sierra Bullets remarks before the data:
http://www.6mmbr.citymaker.com/f/Sierra308Win.pdf
Of course, the 30-06 can shoot the same bullet faster than a 308 with equal pressures; accuracy's another thing.
Jerkface11, I was referring to all rifles (not just service ones) used in both DCM and NRA competition They all shot at the standard USA military A (200 & 300 yes), B (500 & 600 yd) and C (800, 900 & 1000 yd) targets used since the early 1900's. In 1966, they changed to the current SR, MR and LR targets with smaller scoring rings. By then, all the high power records held by the 30-06 were shattered by the 308's. That old war horse never claimed another record in NRA nor DCM/CMP matches.
Saturno, all rimless bottleneck cases have shoulder setback from firing pin impact; new and reloaded ones. It varies with shoulder size and shape plus firing pin impact force and depth into primers as well as cup metal properties. Prime some empty cases then measure their headspace before and after popping them in your rifles.
Here's what I learned from the top few dozen high power rifle competitors back in the 60's through the 90's hangin' out with them at private and social functions as well as at matches around the globe.
If you read my earlier post about match riles and their cartridges, you'll note the 30-06 ones were rebarreled to 308; same rifle but different barrel & chamber and a few functional parts that have no effect on accuracy. That was done with both the M1 service rifles used in DCM and NRA service rifle matches as well as the Win. 70 ones used as match rifles in NRA events.
7.62 NATO barreled M1's needed the barrels gas port drilled out about .035" more to .110" diameter. That ammo had lower port pressure than 30-06. No other changes needed. The USN rebuilt match grade M1's for the USAF teams as well as their own. Tested in accuracy cradles at 300 yards with an excellent lot of M118 match ammo, they shot three 8-round test groups near half the size of what good lots of M72 match ammo did in equal quality Garands; 3" vs 5". Other comparisons at 600 yards shooting both from rests with commercial match ammo, the NATO versions shot about 4" to 5" and the 30-06 about 10" to 11" Twenty-shot strings fired from prone resting rifles on bags shot by top ranked winners and record setters. The new M14NM service rifles rebuilt by Army, Nat'l Guard and USMC shops showed similar accuracy improvement over Garands.
(German Salazar's often referenced comparison was shot in matches and tests with groups 3 to 4 times as big as those shot without human much larger variables degrading accuracy. And he ain't one of those winning the big matches and setting records, either.)
Winchester 70 actions were the favorite for 30-06 NRA match rifles. More reliable, easier to operate and maintain as well as near 3 times stiffer than Remington 700's. To convert one to 308, all that's needed was a new barrel (or set the '06 one back a bit then rechamber it, a 308 extractor clip (with its half inch spacer to stop the bolt for shorter rounds) and a new box magazine with a bolt stop spacer, shorter follower and leaf spring (how Winchester first converted long action 70's to their first push and controlled feed 308's and 243's). A stripper clip guide was screwed down atop the receiver bridge for reloading in rapid fire matches. It held clips just in front of the extractor claw now 1/2" forward of where it was using 30-06 ammo. Winchester's first push feed 308 match rifles's bridge was 1/2" longer forward and it's built-in clip guide positioned clips the same relative to its opened bolt. It was a long action like all their pre-'64 controlled feed ones.
At dinner one night with David Tubb (plus his Dad, George, a top ranked shooter and Mom, Polly, a Nat’l High Power Woman Champion herself), he talked about how surprised both were testing their rebarreled Win. 70 match rifles with a 308 chamber. They tested them from a machine rest shown in the link below with a T2K rifle built by David:
https://www.flickr.com/photos/12787226@N00/sets/72157594303093714/detail/
George Tubb (and several other top ranked master class competitors) had this one made in the late 1950's testing their rifles and ammo. It’s unique design made the rifle recoil back and up like it would fired from the shoulder. 308 ammo from Win 70 based rifles have shot many consecutive 10-shot groups at 600 yards under 2 inches. One string of 40 shots fired in about 20 minutes went into 1.92". No 30-06 has ever shot that well; neither has any modern benchrest rifle I know of.
Sierra Bullets, Lapua and Winchester/Western made the best 30 caliber match bullets in the late fifties and early sixties. A friend who worked at Sierra reloading ammo testing bullets for quality control. He said they used the 30-06 testing all 30 caliber match bullets until the mid fifties after Winchester introduced their 308 Win cartridge. Their first 308 barrel in the rail gun used with 30-06 match grade barrels shot all 30 caliber bullets more accurate than all the 30-06 ones. That 308 case often shot hollow point 30 caliber hunting bullets more accurate than soft point ones. Along with the U.S. Army, Sierra developed their 168-gr. intentional bullet. Sierra was shooting 10-shot groups with 168's in the ones at 100 yards. Ferris Pindell (PPC cartridge founder along with Dr. Lou Palmisano, both benchrest guru's) who worked in Sierra's tool & die shop won a benchrest match with a 308; unheard of at the time as 22 and 6 PPC's were taking home all the marbles.
On a whim, he chambered one 30 caliber match barrel for the 300 savage; the 7.62 NATO's parent case. It also shot 30 caliber bullets more accurate than 30-06 ones in their rail guns. It's not surprising to me that the 30 BR shooting 120-gr bullets in 1:18 twist barrels are virtually equaling the popular 22 and 24 caliber benchrest cartridges. Short and fat cases are best for accuracy. The 30-06, like it's 300 H&H bigger brother favored for 1000 yard matches, got out performed accuracy wise by the 308 and 30-338 and 308 Norma mags' out scored the H&H round. The 308 shot 250-gr. Sierra HPMK's more accurate at 1000 yards than 30-06's with any bullet.
Yes, a 30-06 was used twice in the 80's to win the Palma Match. A friend used it with reduced loads putting Winchester 190-gr. match bullets from Winchester cases out at 2700 fps; something the same barrel will do with max loads and 190's from WCC58 match 308 Win cases. A 30-06 was used in the 1976 Olympics winning the last 300 meter free rifle event the governing committee allowed.
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All the above is a realistic comparison of the 308 and 30-06 for accuracy with minimal influence from humans; when humans aimed the test bed, they did so with minimal accuracy degradation. Primarily the same rifles except for the M14NM.
Until the late 80's, NRA rules allowed any 30 caliber cartridge could be used in NRA match rifle competition; either 30-06, 5.56 or 7.62 NATO in NRA service rifle competition. 99.9% of the top classified competitors chose 308's as their cartridge and shot the best scores with it. 99.9% of matches won at ranges 800 yards and greater were won with the 30 caliber NATO round or its commercial version. Same for match rifle events at shorter ranges but smaller calibers on the 308 parent case were becoming popular as really accurate, long, heavy bullets were finally available in 28, 26, 24 and finally 22 caliber. Their higher BC and milder recoil made them easier to shoot moe accurately. Tested in accuracy cradles, such cartridges were/are no more accurate than the 308. But service rifle long range matches are still dominated on the medal platform by results from 308 cartridges even though 30-06 ammo in Garands could be used.
SAAMI changed their 30-06 chamber throat 2.5 degree angle to 1.5 in the 1980's; same as the 308's. That makes 30-06 rifles shoot a little more accurate. If one cannot make a 30-06 round shoot under 1 MOA at worst though 500 to 600 yards, I doubt that improvement will be seen. It'll be better than the original but still not quite equal 308's.
All cartridges can be loaded with slower than normal powders under heavy bullets. I don't know of any that maintain the accuracy medium speed powders produce. But highest muzzle velocity is more important than accuracy for most people; 6 units of accuracy with bullets leaving 2700 fps and more recoil is better than 4 at 2600.
I've not heard nor read of any new reason some claim '06 cartridges shoot more accurate than 308's for over 20 years. None have panned out realistically. The same ones end up repeating themselves over and over again.
It's not well known that with both at SAAMI specs for barrels and pressure, the 308 puts all bullet weights about 100 fps slower than the 30-06.
While it's often mentioned that the man behind the trigger is the main part of best accuracy, no rifle held by one shoots as accurate as when fired in free recoil untouched by man except by a finger barely touching its trigger. Match rifles testing 1/2 MOA at longer ranges from free recoiling machine rests shoot barely under 2 MOA when hand held by us humans. Us humans don't hold rifles very still.
