6BR vs. 223 Rem and .308 Win — Recoil Comparison
Many visitors to the site ask us, “I’ve got a .223 and .308. What will a 6mmBR Norma (6BR) give me that I’m not getting already?” Well first you will probably average consistently smaller groups than your current .223 or .308 rifle (assuming the 6BR has a quality barrel and trigger). A good .308 Winchester can be superbly accurate, no question about that, but the lesser recoil of the 6BR works in the shooter’s favor over a long string of fire. Even with a Rem 700 or Savage action factory action, a 6BR with a benchrest stock, premium barrel, and a high-quality chambering job should deliver 5-shot groups in the high twos to mid-threes, provided you do your job. We have one 6BR rifle that shoots Lapua factory-loaded 6BR ammunition in the low twos and high ones. That’s exceptional, we admit, but it still shows how the 6BR is an inherently accurate cartridge, even with factory loads.
Compared to a .223, the 6BR offers a much better selection of high-BC projectiles, and will deliver considerably more power on the target. Compared to the .308 shooting 168gr MatchKings, a 6BR shooting 105-107gr bullets offers better ballistics all the way out to 1000 yards. Plus, for most people, the 6BR is just easier to shoot than a .308. Recoil is less than half of the .308 cartridge. Both the .308 and 6BR chamberings offer good barrel life, but the 6BR uses 15-18 grains less powder, saving you money. Here’s how the 6BR stacks up vs. a number of popular calibers:
The comparison of 6BR/Sierra 107 vs. .308/168 MK is a bit specious. In the same 30″ barrel, a .308 shooting Berger 185 BT-LR ballistically beats the 6BR to 1000. Obviously, it has more recoil. The 185 and 107, in their respective calibers, is a more valid comparison.
From the article>>>”Both the .308 and 6BR chamberings offer good barrel life, but the 6BR uses 50% less powder, saving you money.”<<<
***Depends on your deffinition of "good barrel life" (Putting 2,500 and 5,000+ in the same category is a bit decietful)and how you calculate cost to include a new barrel or not. 6BR 2,500 barrel life vs .308 5,000+ barrel life. Will you save enough on 50% less powder and projectile costs to pay for a new barrel job? Also, with the same ammount of shooting the 6BR will be in the gunsmiths possession and not your possession 2x as much time with only half the barrel life. Pretend they rented guns for competitors who had their guns in the shop. Calculate gun rental charges into the equation just for spits and giggles.
EDITOR: On average, I would agree that a .308 barrel would outlast a 6mmBR barrel. But the 5000-round .308 barrel life is a “maybe”, not a “given”. One has to consider what the accuracy expectation is. Plenty of hot-loading Palma guys are screwing on a new tube at 2300 rounds, and there are some 6BR-shooting varmint guys who are at 3000+ rounds and still getting 1/2 MOA. But your point is well-taken that one should consider barrel life in the whole equation.
See: http://bulletin.accurateshooter.com/2011/07/barrel-depreciation-and-the-true-cost-of-shooting/
Steve Blair wrote: “The comparison of 6BR/Sierra 107 vs. .308/168 MK is a bit specious. In the same 30″ barrel, a .308 shooting Berger 185 BT-LR ballistically beats the 6BR to 1000. Obviously, it has more recoil. The 185 and 107, in their respective calibers, is a more valid comparison.”
Specious? Read on…
Steve, since you picked a Berger, I’ll pick a Berger 105 VLD (as the article says 105-107 gr bullets). You may be surprised, but the 6BR still beats the .308 with 185s. Here is data from JBM Ballistics, http://www.jbmballistics.com, using Litz field-tested BCs.
6BR, Berger 105 VLD, 2910 fps MV, 70deg temp, sea level (my personal match load — and plenty of guys are loading faster.)
6BR Drop @ 1000 yards from 100yd Zero = 28.5 MOA
As to the .308 Win, the highest velocity with 180gr-class bullets on the Hodgdon Reloading Center was 2683 fps with compressed MAX load of IMR 4064. Giving you, generously, another 50 fps for the long barrel, let’s use 2733 fps.
.308 Win, Berger 185 LR Boattail, (2733 fps MV, 70 degrees, sea level)
.308 Drop @ 1000 yards from 100yd Zero = 31.9 MOA
SUMMARY:
6BR = 28.5 MOA drop @ 1000
.308 Win = 31.9 MOA drop @ 1000
Guess What? Even using YOUR choice of 185 Bergers, the 6BR still yields better ballistics, just as the article says. Run the numbers through JBM yourself — or any other program with G7 BCs for that matter. As for the real world — we’ve shot the 185 at 1000 (from a 30″ .308) and yes it did require more clicks than my 27″ 6BR. Regarding real world .308 velocities, I picked the fastest “book load” I could find, a MAX compressed load, and then added 50 fps. That seems fair.
It would be fun to compare the .308 with a Dasher running 3040 fps with the new Berger Hybrids — the “drop gap” would be even bigger!
EDITOR
@ the EDITOR,
You got the exact article I made my point from ; )
I also used the avg BBL life numbers from The 6BR tab http://www.accurateshooter.com/cartridge-guides/6mmbr/
>>>”The 6BR offers easy load development, excellent barrel life (expect 2500 rounds or more of top accuracy),”<<>>”The .308 Win delivers superb accuracy along with outstanding barrel life–it’s not unusual for a .308 barrel to return 5,000+ rounds of accurate”<<< service.
EDITOR: To say that “it’s not unusual” to see 5000 rounds of accurate service is hardly the same thing as asserting that any and all .308 barrels can be counted to yield 5000 or more rounds of top-level competitive accuracy. And in general the levels of accuracy demanded from a 6mmbr barrel used in benchrest comps may be greater than the expectation of the typical .308 shooter who may be quite tickled to have 1/2 MOA accuracy. The most demanding .308 shooters today are probably F-TR shooters. Hopefully some F-TR shooters can share their experience as to how long their barrels give first-tier accuracy in that discipline. But I’m sure we can agree on one thing — that not all barrels, even from the same manufacturer, in the same caliber, are equal.
I think the variances on barrel life are not only velocity, powder charge and cleaning routine which are no doubt very important,but also rifling method. I have worn out no less than 30 barrels of all types and can say that cut rifled barrels last me 10%-20% longer useful life than button rifled barrels. ( I make no argument on accuracy as I have had hummers from both rifling methods )
TYLER: Editor, your 6mm load may be 2900 fps, and the Hodgdon load+50 fps may be honest numbers, but still low compared to my loads.
I load Varget and with 175s I can get 2900 fps before I see pressure.
Editor: Tyler, since every barrel is different I won’t contest what you say. However, running Quickload for a .308 Win shooting 175gr SMKs (loaded long with .250 of shank in the neck), shows that a load that yields 2900 fps velocity in a 30″ barrel would develop 68,980 psi peak pressure — that’s way, way above max. Quickload is not a perfect predictor by any means. But, generally I’ve found it to be accurate within plus/minus 30 fps. If I lower the velocity to 2870 fps (allowing Quickload a 30 fps ‘fudge factor’), Quickload still indicates pressures in excess of 66,000 psi, again well over the 60,191 psi rating of the cartridge. Hence I would caution readers about attempting to load to these velocities in their gun!
TYLER: With RL 17 and 208 grain Amaxes I get over 2800 fps (albeit a tad bit of pressure there, but not loosening primer pockets after several firings). This is with Lapua brass and a 30″ barrel that has been smoothed with Tubb’s bullets. Maybe not typical, but safe in my gun, and changes the ballistics quite a bit.
Editor: Because I don’t have Reloder 17 in my Quickload database, I can’t run a Quickload Calc on your 2800 fps load. RL17 powder is quite unique, as we all know. But I caution all readers who think they might reach those numbers with some other powder. Running Quickload, I couldn’t find ANY other powder that could yield even 2600 fps (with Amax 208s) at safe pressure levels. In fact, to get up to 2700 fps with the 208gr Amaxs and Varget, you’d be running 73,100 psi according to Quickload — that’s very dangerous. To put this in perspective, the fastest MAX load listed on the Hodgdon reloading site for the .308 Win and a 200gr bullet (not even a 208gr) is 2582 fps, and that’s at 60,600 psi (rated max) with CFE 223. You say you’re running 218+ fps faster than that with Reloder 17. I know RL17 can give considerably more velocity, but again I suspect you are actually running extremely high pressures. I advise all readers to exercise EXTREME CAUTION — and don’t expect to achieve 2800 fps with a 208 grainer in your .308 Win rifle!
Tyler, I debated whether to post your comments because your numbers are really “off the chart”. One of our most skilled testers, who uses 210s in a .308 said that your numbers “were about 250 fps high” and he advised you to test with a different chronograph. IF your chron numbers are valid, please be careful. I suspect that, if you were to put a pressure gauge on your rifle with those 208gr Amax loads, you might see pressure numbers that were well above safe levels, a far cry from a “tad bit of pressure”. To reinforce this point, Alliant’s published RL17 max load for a 180gr BTSP Speer in a .308 Win clocks 2641 fps in a 22″ barrel. You’re running a 28gr heavier bullet and purportedly pushing it to 2800. Frankly that’s pretty scary even if you’re getting some extra speed from your 30″ barrel.
NOTE to readers — as always, start low and work up, and refer to published, well-established and tested loads to get a realistic idea of safe load limits.
Kevin Thomas did an exhaustive test of 5, 308 barrels & documented the entire procedings & results in Precision Shooting. All the 308 barrels were “done” at around 4000 rounds. Don’t know where the 5000 round number came from. Want to state some verifiable references?
Well the 6 Norma BR doesn’t use half the powder of the .308. Common loads are 30 grains of Varget in the 6 BR with the 107 Sierra MK and 46 grains of Varget in the .308 with the Sierra MK Palma 155. Both bullets have the same BC and near identical velocity, 2900-3000fps in 30″ Krieger. My .308 Palma and 6 BR both shoot 1/2 minute. So I find them pretty close with the exception of recoil witch is heavier with the .308 but far from a problem.
EDITOR: We didn’t say the 6mmBR used half the powder — we originally said 50% less based on a 15 grains difference which is 50% of a normal load in the 6mmBR. But since this may have been confusing the way it was stated, I changed the article to read “15-18 grains less” and we’ll let readers figure out the percentages. Thanks for the clarification.
Both seem to go 4,000 rounds
Opinions:
Peak accuracy of a 6br w/30gr Varget ~2500 rds
Peak accuracy of a 308 w/46gr Varget ~2800 rds
4000 from either, while accurate enough for many, is well beyond peak accuracy.
I don’t compete, and wouldn’t with a .308 no matter what. But if i did, I’d be changing barrels by 3000
Mmmm,
Pretty elementary physical description of what’s going on. Exactly how did you calculate these figures? Did you just do a momentum calculation and then give the maximum attained free recoil velocity of the rifle and convert this to the free recoil energy? Did you use the same mass rifle each time? What propellant gas exit velocity did you use? Was it modified for varying muzzle gas pressure? Slightly worrying that the comparative graph describes recoil energy as a force, they are not one and the same, a basic science error there. Also, the exact recoil force experienced would vary over time, you’d be better to state the momentum, or even better, the impulse to the firer. Though this would require the rifle to be instrumented with accelerometers; at least one axis (axial, along the barrel line). The data takes no account for muzzle brakes or buffers, but in general these aren’t used for the type of shooting undertaken here, so can be dismissed.
The Recoil Energy is Calculated using the Point Blank Ballistics Program. It does the calc with four inputs: Bullet weight (grains), Bullet Velocity (fps), Powder Weight (grains), Total gun weight (pounds). It resolves recoil energy in ft/lbs and recoil velocity in fps.
Paul,
With my 6 dasher I’m running the 105 Berger Hybrids at 3,050 chrono’d 15′ from the muzzle and I shot 1K practice three weeks ago in 28º – my come-up was 23.75moa from a 100yd zero. Typical.
The whole thing weighs 22lbs……what is this recoil you speak of?
You don’t have to sell me on the virtues of a 6BR, I know them and I live them. Pedantic argumnts about powder and barrel lives is tediously irrelevent. If you want to compete in FTR, TR or Palma, use a 308. Cheaper bullets, better inherent accuracy less powder less recoil and way easier to make work puts the 6BR the one and only choice for me personally.
In fact, the fewer people out there using the 6BR the better. Componenets are getting hard to find.
Go with a 308.