Cartridges: Sibling Rivalry: .308 vs. .30-06

Sibling Rivalry: .308 vs. .30-06
by Germán A. Salazar

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Frankford Arsenal .30-06 Match - Lake City .308 Match


Middleton Tompkins 1958
Introduction
In 1956, eighteen year-old Middleton Tompkins won the NRA Junior Highpower Championship with his .30-06 Winchester Model 70. Two years later in 1958, by then out of the Junior ranks, he won the overall championship. At that time .30 caliber shooting, as Highpower was commonly known, was strictly a .30-06 proposition. However, the .308 was on the horizon and shooters were aware of its potential. After a few years away from the winner's podium and looking for an edge, Mid put together one of the first .308 bolt-action match rifles and used it to win the 1963 NRA Highpower Championship, the second of his six overall victories (1958, 1963, 1964, 1967, 1968, 1982); it was the first ever win for anything other than the .30-06 in the Highpower championship.


Middleton Tompkins 1963 Highpower Bolt Gun Champion
with Service Rifle Champion Kruk.

I recently asked Mid about his decision to try the .308 in 1963. He said: "At that time I was doing a lot of testing for the Air Force on the AR15 and we shot the M14 a great deal to compare them. That made me think the .308 would be a useful cartridge for Highpower bolt-gun shooting. The rule book said the cartridge had to be .30 caliber, but it didn't say it had to be a .30-06. We built a .308 Model 70 and in all our testing, it outshot the .30-06, so I took it to Camp Perry. I'm pretty sure it was the first one there." Mid described making a clip slot for the rifle from a piece of aluminum using only a few files. He needed the extended, bolt-on, clip slot rather than the one cut into the action in order to position the shorter .308 cartridge at the front of the magazine box. Roy Dunlap saw it at Camp Perry and began making them commercially. Mid said "Roy made the best clip slots for the .308 conversion."

That long-ago summer day at Camp Perry changed NRA Highpower shooting forever; over fifty years of unchallenged .30-06 domination quickly came to an end. Eventually, in the mid 1980's, the NRA would drop the .30 caliber requirement altogether for across-the-course shooting, opening the door to the sub-caliber gamesmanship approach to Highpower. Those who adopted that view shifted from the .308 to the 7mm, 6.5 mm and 6 mm cartridges and began to dominate the top of the results sheets. The final slap in the face to us .30-06 shooters came a few years later when the NRA dropped the .30-06 as an eligible cartridge for Palma shooting. I shoot with Mid frequently and often jokingly remind him that the whole sub-caliber craze is his fault!

The Eternal Debate
Notwithstanding the .30 caliber cartridges' fade-out from NRA across the course shooting, for the past five decades, shooters have argued over the relative merits of the .308 versus the .30-06. That argument isn't likely to be settled in our lifetimes. That's a good thing, after all we need something to talk about after were done shooting and I've certainly been involved in many of those discussions - I might have even instigated a few... It isn't quite the Civil War, pitting brother against brother, but more than a little heat has been generated by some of those friendly debates. The problem with those arguments, however, especially those on the internet, is the lack of a common set of standards - sometimes it seems as though we're all talking past each other.

Middleton Tompkins and German Salazar - April 1, 2011
It's impossible to have a universal basis for comparison when some fellows who are recreational benchrest type shooters and want to measure a few groups at 100 yards, others like to shoot a bit further to let these cartridges stretch their legs. A few want to compare available factory match ammo. Then there are the hunters who want to talk about terminal ballistics and the military buffs who want to know which cartridge legendary Marine sniper Carlos Hathcock used in Vietnam (both) or what snipers use today. Apart from differing standards of comparison, most people want to base their analysis on far too little data. They want their single highest score or best group to represent their favorite cartridge's capability - that's simply not realistic, nor statistically sound.

The one group of shooters we don't hear from too much in these discussions is Highpower shooters and the reason is simple: both cartridges are now essentially obsolete for NRA across-the-course Highpower shooting. In prone matches we see a bit more use of the .30 caliber. The .308 is required for Palma shooting, so it is also used by many Palma competitors in other long-range and mid-range prone matches. However, the .30-06 is well and truly dead except for a handful of hard-core .30 caliber shooters - a proudly stubborn group among which I count myself.

I'm not a benchrest shooter, nor am I a hunter, nor do I shoot factory ammunition, nor do I participate in any form of competitive shooting other than NRA Highpower prone - I just don't have the time. However, when it comes to NRA Highpower prone, whether mid-range or long-range, I think I can offer some useful thoughts to those who are interested in learning more about how these two cartridges compare. Accordingly, our cartridge comparison will use scores fired in NRA prone Highpower matches as the basis for our accuracy comparison. Apart from the fact that I have a good database of scores to use for this purpose, I believe that scores offer a more meaningful measure of accuracy than group sizes; after all, a score counts every shot, whereas a group accounts only for the two worst shots. This is perfectly analogous to the difference between extreme spread and standard deviation when measuring muzzle velocity.

All scores were fired in competition, with iron sights, from a sling supported prone position. Each cartridge was fired with two well built rifles over a period of 27 months of cold, hot, windy, calm and sometimes dangerous weather. The total number of rounds analyzed was 4,800 rounds at mid-range and 1,310 at 1000 yards for a total of 6,110 rounds. That's a bit more than most internet debaters manage to fire to support their reasoning.

Gilkes actions in .308 and .30-06 Match Rifles

Setting Standards
I have two pairs of identical rifles differing only in the chambering; one pair has Gilkes actions in Robertson synthetic stocks, the other pair has Borden actions in Eliseo tubegun stocks. One rifle in each pair is chambered in .308 and the other in .30-06. Clark Fay used the same two reamers for each pair of rifles; the .30-06 with the PTG Serengeti match reamer and the .308 with a tight-neck, slightly long-throat reamer we worked up together. All four rifles have Warner rear sights, Riles front sights and a roughly similar number of rounds fired through their barrels. Those four rifles form the basis for my comparison of the two cartridges for NRA Highpower prone shooting. As an added point of interest, I've also compared the scores from the .308 and the .30-06 to the scores I've fired with my 6XC rifles in order to compare the old stalwarts against a fairly representative modern sub-caliber cartridge.

Eliseo CSS Tubeguns with Borden actions - .308 and .30-06
Most shooters who ask me about the .30-06 want to know whether the recoil is uncomfortable; the short answer is no. Although the straight-line design of the tubegun stocks seems to reduce the felt recoil a bit, it isn't bothersome in either type of stock. Compared to the .308, with the same bullet weight, you feel more pressure from the handstop, but not particularly more in the shoulder. The more significant difference is the amount of muzzle movement during barrel time; when the shot breaks while the barrel is still moving, the .30-06 will usually deliver the shot a bit further from center than the .308 which has less muzzle movement. As long as the shot is broken with a still muzzle and with good follow-through, the increased muzzle movement during barrel time won't be a problem. Uncomfortable recoil isn't a concern, but the need for highly refined shot execution skills is both the limitation and the opportunity presented by the .30-06.

Gilkes 6XC and BAT 6XC
Let's get on with the score comparison and then we'll give it a bit of analysis. At the bottom of the article you'll find a series of charts, these contain all of the scores that I've fired in competition since January of 2009 with these rifles - no scores were omitted. Some days were windy, some were brutally windy, a few were calm, some days I was trying new loads or new bullets, some I used well known loads. The point is that everything is in the mix and over a large number of matches, it averages out quite well.

Mid-Range Comparison
In NRA Mid-Range matches (500 and 600 yards), the average score and percentage of possible score for each cartridge was as follows:

.308 - 597-36X (99.5%) 960 rounds fired
6XC - 596-35X (99.3%) 1260 rounds fired
.30-06 -  595-31X (99.2%) 2580 rounds fired

Interestingly, the high X count (44X) was reached with all three cartridges. During the time period under review, I shot three scores of 600 with the .308, one 600 with the 6XC and none with the .30-06. Over the years I've shot 23 scores of 600, but only one was with a .30-06 and that was about 15 years ago.

If we look at the score averages, the .308 comes out on top at the Mid-Range distances. The average for the .308 is composed of a smaller number of scores because I tend to shoot the .30-06 more often, but I think it's a large enough sample to be reasonably accurate so the Mid-Range win goes to the .308 by 0.3% of the possible score. By the way, notice the the 6XC, as good as it is, simply straddles the .30 caliber cartridges, it is not the winner - that may surprise some people. When you factor in the shorter barrel life of a 6XC compared to the .30's, that becomes something to really consider when selecting a cartridge for Mid-Range matches.

Long-Range Comparison
I rarely shoot the .308 in matches that are only 1000 yards; most of my 1000 yard .308 shooting is done in Palma matches which include 800, 900 and 1000 yards. As most of you know, the .30-06 and 6XC can't be used in Palma matches. This creates a small difficulty in score comparisons because Palma matches have 15 shot stages and 1000 yard matches have 20 shot stages. To make the comparison useful, the Long-Range results are presented only as a percentage of the possible score and the 800 and 900 yard stages of Palma matches were not included in the comparison (although they are shown in the charts, they were not used in calculating the averages).

In NRA Long-Range and Palma matches, the average percentage of possible score for each cartridge at 1000 yards was as follows:

6XC - 98.9%, 360 rounds fired
.30-06 - 97.7%, 460 rounds fired
.308 - 97.3%, 490 rounds fired

As you can see, the .308 went from the top of the list at Mid-Range to the bottom at Long-Range. This isn't too surprising when one considers its limited case capacity for the bullet weights typically used in Long-Range shooting. They just run out of steam and dip perilously close to the transonic range as they approach 1000 yards of flight (see this earlier article for more information on transonic problems). The extra 150 fps or so that can be safely obtained from the .30-06 case really pays off at 1000 yards. Unsurprisingly, the 6XC which moves light, high BC bullets at an even higher MV than either of the .30's comes out on top. I used the 6XC to win the Arizona Long-Range State Championship a few years ago and remain confident that it is a top choice for NRA Long-Range competition.

A Few Concluding Thoughts
Although I keep a log of all my scores, I hadn't calculated the percentages prior to preparing this article. However, I wasn't particularly surprised by the results; the .308 has always been a tremendously accurate cartridge at 600 yards, Mid's conclusions from 1963 remain valid today. I was a bit surprised that the 6XC wasn't the top dog at Mid-Range, but that simply shows that our pre-conceptions can be wrong and data matters. At Long-Range, the cartridges finished in the exact order that I would have predicted. I know the 6XC is a great LR cartridge, and my results with the .30-06 at 1000 have been very satisfying, so there were no surprises there. That's not to say some other people won't be surprised by the outcome!

So how much do these differences matter? It depends a bit on your level of shooting. Many of the Mid-Range matches shown in the charts were won or lost by a point, plenty more came down to the X count. When you're fighting for the overall win at 500 or 600 yards, every point and every X makes a difference. However, all three cartridges are remarkably close; I believe this reflects the fact that ballistics are relatively less important than pure shooter skill in Mid-Range shooting. With the same shooter behind the buttplate for all three cartridges, the results are predictably close. As the charts show, I shoot the .30-06 a lot more than the other cartridges, the simple reason is that the extra challenge of doing it with the .30-06 makes the wins all the sweeter, so I keep at it.

In the Long-Range matches, the spread between the cartridges is a little bigger, reflecting the increased importance of ballistics when the range gets stretched to the maximum. So even with the same shooter firing all the rifles, the differences become more pronounced. Many modern-day competitors look down on the .30-06 as a long range cartridge, but I'll definitely say that if you want a good shooting cartridge with excellent barrel life and a huge choice of components, you can't do much better than the .30-06 for all around use.










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The Logical .30-06
Accuracy Secrets of the .30-06 - Part 1
US National Match Ammunition

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