155,5 gr Bergers or 185 gr BT Bergers?

[casspir]

Without bullet weight restrictions in F/TR 308, what bullet is the most accurate in all conditions - the 155,5 Berger or 185gr Berger BT? I asked Bryan Litz and I agree with him that the BC on the 185gr is optimum for my 1:12 Broughton 5C barrel-and shot with a PALMA chamber. To compare, if the 155,5 gr Bergers were shot in a 1:14 twist barrel(also with a PALMA chamber) what would be the most accurate of the two? Would it be too marginal to mention? I would think the 185 gr because of the excellent BC. But I certainly don`t know everything. What is the view point of the readers?

 

[wolfman]

I think you are going to see a lot of experimentation w/ heavier bullets in F/Tr over the next little while. During the '09 FCWC, the vast majority of shooters were shooting one ofr th 155 class bullets. There were a few shooting heavies, including the guy who placed 2nd overall. While most of us were shooting the 155's, there was lots of buzz about the heavies, and that seems to have continued. When I'm ordering a barrel, I decide what bullet I hope to shoot, and then order what I think is the optimum twist for that bullet. Determining the optimum twist can be a rather elusive, but Mr. Litz's recommendation is always tough to ignore.

 

[HPMike800]

I was facing the same choice when I barreld my Palma rifle. I think both bullets out of a 308 are just as accurate. The question is wind drift. I called a national champion and he shoots 185's and said they do shoot inside a 155. By the math they do but not by much unless you push them pretty hard. In the end, at my skill level on the iron sights target I did not think I would see much of a diffrence. So I went 155's since their cheeper and have less recoil.

I picked up a 1:12 barrel and a went a Palma 95 chamber. When I get to 2,500 on the gun I may have the barrel set back and set up for 185's just to see.

Don't be to worred about a little over spin. I would much rather have a little to much than be a little underspun.

 

[Laurie]

Several registered GB F-Class Assoc F/TR competitors are likely to switch to heavy bullets this season. While the UK, European, and World Champion Russell Simmonds was quite unbeatable with a 1-14" twist barrel and 155s, much of that is down to Russell's unbelievably good wind reading skills. The rest of us need a bit more from the equipment just to narrow the gap a little!

F/TR World Championship Silver Medal winner George Barnard is a long-time Bisley 'Match Rifle' (1,000-1,200yd with .308W and with barrel weight restrictions) shooter and brought his long barrel, high-velocity heavy bullet philosophy to F/TR - and it works for him. His bullet of choice is the 200gn Sierra MK, which although not the best in class for BC was found by the MR guys to give optimum performance at 1,000yd + at Bisley (but pre the latest generation of high-BC tangent ogive bullets from Berger). A GB FCA team training weekend last March at Bisley saw the shooting take place in really dire wind conditions - near gale with large amounts of gusting. Bad enough for national team members to get complete misses. The shoot was 2 sighters; 15 score and the story goes that George only brought 12 cartridges, not 17, but still got the highest F/TR score in these conditions! I was told how much less windage he needed than the 155gn users, but forget it now. Without detracting from Mr Barnard's plentiful shooting skills and his great experience of Bisley, there is no question that his bullets were shooting way, way inside everybody else's.

Accuracy of the 185 Berger? I did some 100yd load testing last autumn off the bench with these bullets in my 1-13.5 Bartlein 30" and got superb accuracy at 2,810 fps which in ME terms is almost a direct match to my 155gn Lapua Scenar load. There was an issue over whether this twist rate would stabilise the bullet, but it did at the time of the tests, alongside the 190gn Sierra MK. This is despite Miller's twist rule giving an Sg of only 1.03 or thereabouts at standard temp and pressure. However, when I tried the load a couple of weeks later at 900yd I had to abandon them and return to 155s, presumably because temperatures had dropped from the high 50s to low 40s (F) and previously marginally stabilised bullets were now marginally unstable. They hit the target but struggled to stay within the three ring (second out from the bull as we work on Bull = 5) with the dispersion as much vertical as horizontal despite MV ES values under 10 fps.

So, 2010 will see a 1-10" Broughton tried with everything up to 210gn VLDs, but the 185s probably the primary bullet. I did a table (below) which was primarily about 223 / 90gn v 308W with a variety of options, but it shows the 185s only give a little away to the 208 A-Max and 210s from Sierra and Berger. All MVs are based on equivalent MEs to a 155 at 3,050 fps which is a little modest by GB FCA F/TR standards, 3,050 - 3,100 fps being the norm at national league level.

On twists, Bryan Litz tells me that he and other Palma / Fullbore shooters use their 1-13" twist rifles without problems in the US summer where no bullet weight restrictions apply - this ties in with my 1-13.5 experience, but neverthless, he is considering a move to 1-12" and doesn't believe that will affect the lighter bullets adversely. As well as the 185 Berger, I know from personal experience that this twist rate works very well with the 190gn Sierra, another fine long-range performer.


F/TR Bullet Ballistic Efficiency

Bullets ranked in descending order of performance judged by Deflection in 10mph Crosswind at 1,000yd

Bullet Make, Model & Wt (Best in Class) I7 Value V0 V1,000 D1,000 (Inches/MOA)

.308 Winchester

*Hornady 208gn A-Max 0.967 2,630 fps 1,417 fps 72.74” / 6.9

Berger 210gn VLD 0.979 2,620 fps 1,407 fps 73.42” / 7.0

Berger 190gn VLD 0.982 2,755 fps 1,392 fps 77.92” / 7.4

Berger 185gn BT M L-Range 0.972 2,790 fps 1,398 fps 78.15” / 7.5

*Sierra 240gn MatchKing 1.092 2,450 fps 1,307 fps 79.35” / 7.6

*Sierra 220gn MatchKing 1.068 2,560 fps 1,322 fps 80.66” / 7.7

Berger 175gn BT M L-R 0.999 2,870 fps 1,454 fps 83.93” / 8.0

*Sierra 200gn MatchKing 1.058 2,685 fps 1,317 fps 84.10” / 8.0

Lapua 155gn Scenar
Berger 155.5gn M Target FB 0.988 3,050 fps 1,331 fps 89.04” / 8.5

Berger 168gn VLD 1.047 2,930 fps 1,282 fps 92.28” / 8.8

*Hornady 178gn A-Max 1.118 2,830 fps 1,213 fps 98.54” / 9.4

*Only suitable long-range bullet available in this weight in the UK. Note – no suitable 180gn L-R bullet.

MVs
155gn @ 3,050 fps used as a base. Other MVs calculated to produce the same ME (3,200 ft/lbs).


.223 Remington

Berger 90gn VLD 0.911 2,825 fps 1,401 fps 78.53” / 7.5

Berger 90gn Match BT L-R 0.979 2,825 fps 1,314 fps 87.16” / 8.3

Hornady 80gn A-Max 0.987 3,000 fps 1,266 fps 94.97” / 9.1

MVs
Assumed on the basis of Jerry Tierney’s Palma Rifle work at Sacramento. 80gn bullets gave good accuracy at around 3,000 fps and 90gn VLDs at 2,830 fps. (Higher MVs are obtainable.)

Free-Recoil Comparisons (18lb Rifle)

.223 Rem 90gn 2,825fps 2.5 ft/lb
.223 Rem 80gn 3,000 fps 2.5 ft/lb
.308 Win 155gn 3,050 fps 9.2 ft/lb
308 Win 208gn 2,630 fps 9.8 ft/lb
Calculations: Sierra Infinity VI ballistics program



Data Sources & Assumptions
Bullet efficiency and ballistics performance from Bryan Litz’s book Applied Ballistics for Long Range Shooting and its associated G7 PC program.

.308W MVs based on 155gn at 3,050 fps MV (norm in UK F/TR ±50 fps) and other bullet weight MVs are calculated on the basis of those that produce the same ME as this base combination. (Actual results from use of 185 and 210gn bullets supports the methodology.)
.223R MVs are those found to give good results in Palma type rifles in tests by Clint Dahlstrom (Viht N550) and Jerry Tierney (Viht N550 + Alliant Re15) in 2008/09 tests. Higher MVs were found achievable, but 90gn VLD MV/accuracy seemed to peak at a bit over 2,800 fps.




Laurie,
York, England

 

[casspir]

Thanks to all the opinions expressed here. Still, the bullet drop of the 155,5 Fullbore - according to the Berger Ballistic Program (that can be downloaded) the 155,5 with a BC of 0.464 at 3000fps the drop is 214,94" and drift 35.87" and the drop of the 185 BT at 2746fps is 248.26 and drift is 32.92 in a 10mph wind. Seems to me that the 155,5 is a much better bet.The 210gr with a bc of 0.616 at a velocity of 2577 drops 278.76 and drift is 32.38. Doping the wind is marginal but recoil is much less and bullets might be cheaper too. I am no PRO, but it seems the choice is obvious. Again I might be hoplessly on the wrong track!

 

[js223]

casspir, since you mentioned F/TR that means known-distance target shooting. Given that, I'm curious why you think flatter shooting yet more wind deflection makes the 155.5 a much better bet than the 185? Flat shooting is a non-issue in F-Class, but wind deflection most definitely is.

 

[casspir]

js223,
I am not advocating one bullet above the other. I have absolutely no authority to do so and no interest in it either. I am merely stating that the 155.5 Full Bore Berger`s with a lot less recoil that the 185 BT Berger`s only drifts 2.95" more on a 1000 yards. It seems insignificant to me. If the 155.5 has a lot less recoil and are probably more economical to shoot why then consider the 185 or 210 grain bullet for that matter? That brings me to my question posted. If the 185 BT bullets ( with the correct twist) are indeed shooting smaller groups than the 155.5`s then there is all the motive in the world to shoot them. Again, I am no Pro and Bryan Litz should probably give us his comments here. As Laurie said, a lot of testing will be done here during the next season .

 

[Bryan Litz Ballistics]

Good discussion guys.

This is a discussion that could be debated till the end of time if we only consider the raw ballistics. There is no universally 'right or wrong' bullet for everyone to shoot.

In my opinion, the right way to think about this question is to consider your personal shooting objectives and goals and decide which performance is optimal for your application. There are good reasons to shoot light bullets and good reasons to shoot heavy bullets. Below is a list of pro's and con's for 155/155.5's.

Pro's for 155/155.5 grain bullets:
1) Lighter recoil. This is important it you, personally, are adverse to high levels of recoil. If you're not, then this is a non-issue.
2) Flatter trajectory. If you're shooting tactical matches where you encounter targets at unknown ranges, then the flat trajectory is an asset. However if all your shooting is done at known ranges with sighter shots allowed, then a flat trajectory is irrelevant (as stated above).
3) This class of bullet is eligible for international competition. If it's your goal to shoot in FULLBORE events and/or events outside the US, then you need to load bullets that weight less than 156 grains. This is not an option, but a requirement.

Con's of the 155/155.5 grain bullets:
1) Greater wind drift. Although this is the only con I can think of, it's a major consideration for anyone engaged in shooting long range targets. Consider the points lost by the top 10 shooters in any major tournament. Almost every point is lost to wind. Clearly if the wind deflection can be minimized, you stand to drop fewer points in uncertain wind conditions.

As to the inherent accuracy, I don't think one bullet has an advantage over the other. If a shooter is averse to high recoil, he may not be able to shoot the heavy bullets as well as the light ones, but that's not a property of the bullet, it's a property of the shooter. I've added weight to my rifle to make it more comfortable to shoot the heavy bullets.

Stability requirements are a consideration, but like recoil, they're not a pro or con for either bullet. If a proper twist is selected for a bullet, it will shoot well. I've been shooting 185's in my 1:13" twist (which was originally selected to shoot 155/155.5's) but my next barrel will be a 1:12" twist which is better for the 185's, and won't affect the performance of the lighter bullets in events where the rules dictate their use.

Let's take a closer look at wind deflection, since it seems to be the only advantage of shooting the heavier bullet. Laurie's sharp analysis above indicates 11" less wind drift (78.15" vs 89.04") for the 185 in a 10 mph crosswind at 1000 yards. That's a 12% advantage in favor of the heavy bullet which applies to any wind condition (pick-up, let-off, etc) at that range. Considering that most matches are won or lost based on how a shooter performs in the wind, 12% is quite significant. It means that if someone has ballistics that are effectively 12% better than yours, you have to read wind 12% better than them just to achieve equality! Do you want to bet that you can read wind 12% better than the top shooters?

But it gets better. Laruie's fine analysis is based on the assumption of equal muzzle energy, which is the same as loading to equal chamber pressure. This is a good technique to get in the ballpark of expected velocities for different weight bullets, but sometimes the real world intrudes and throws us a curveball (sometimes in our favor, sometimes not). With 155.5 grain bullets, I can fill the case to 100% load density and achieve about 3020-3030 fps and see no excessive pressure signs, which means there's potential for more speed. When shooting 185's, I can get enough powder in the case to achieve a truly max pressure load, which exceeds the pressure of my load with 155.5's. The effect is that I can shoot the 185's at a higher speed than projected by the equal ME assumption; about 70 fps faster. With this information, the wind deflection of the 185 falls from 78.15" to 74.8", and the analysis relative to the 155.5 grain bullet changes to 16% in favor of the heavy bullet!

Granted, much of the preceding paragraph is specific to my rifle/throat, and brand/lot of powder. It does indicate one case where you can get more than expected from the heavy bullet and overshadow the 155/155.5's by an even more profound margin.

From a 'strategic' point of view, when you go to a long range (known distance) match with <156 grain bullets where there's no restriction on bullet weight, and you want to win, you're gambling that you can read wind at least 12% to 16% better than the top shooters who are shooting heavier bullets.

To take a step back and review...

If you're averse to high recoil, the 155/155.5's are probably a better option for you than the heavier, high recoiling bullets.

If you shoot in tactical matches where the distance is unknown, the flatter trajectory of the 155/155.5's is a considerable asset and they're probably a better bullet for that application.

If you shoot in FULLBORE / international LR events, then you're restricted to <156 grain bullets and don't have a choice.

If you're a typical KD long range shooter (Palma or F-TR) who's not bothered by the recoil, and doesn't care to standardize their equipment for international competition (or maintains a separate load for those shooting events), the heavy bullets are the best option for minimizing wind deflection which is a decisive measure of ballistic performance in LR shooting contests.

Have a good weekend,
-Bryan

 

[JERRYHM]

Casspir,
Where did you get the wind drift numbers? In a 10 mph cross wind the drift number should be around 76 -77 inches at 1000 yards for the 185.

The difference between the 155.5 and the 185 will be about 12 inches of wind drift at 1000 yards.

 

[dnirode]

Lets for the sake of arguement, take a look at calculated recoil velocity. As a former tac team rifleman I have fired a LOT of .30 caliber rounds down range and have come to realize that heaviest bullet in a particular cartridge is not always the hardest recoiling. A lot of the equation is the loading used and the weight of the rifle. That being said lets look at numbers.

Using the same rifle that weighs 12.5 pounds and a middle of the road velocity load of 2920 fps with a 46.2 grain load of RL15 for the 155.5 grain bullet listed in the .308 Win load data section of this site and a load for the 185 grain bullet of 2620 fps with 44.0 grains ofIMR 4064 which is a standard long range 1000 yard load used by others.

155.5 - 46.2 x 1.75=80.85
add bullet weight =236.35
multiply by velocity = 690142
divide by wt of rifle =55211
divide by 7000 (grains in lb) = 7.88

185 - 44.0 x 1.75 = 77
add bullet weight = 262
multiply by velocity = 686440
divide by wt of rifle = 54915.2
divide by wt of rifle = 7.84

1000 yd numbers taken from JBM:
155.5- 31.6 moa elevation
1253 remaining vel
9.1 moa drift/10mph

185.0- 36.2 moa elevation
1259 remaining vel
8.5 moa drift/10mph

Now the loads used/wt of rifles/velocity obtained from a particular barrel/atmospheric conditions may be different from one test to another but the advantage of 1/2 moa less wind drift might save your score with a missed wind call and the recoil difference is a wash. Besides, like js223 said you are shooting at a known distance. Once the zero is obtained only changes for light, temperature or humidity need to be made for elevation. Hope this helps a little. Let us know how it works out for you.

Dave N.

 

[casspir]

JERRYHM,
It was from a Berger Ballistic Program I downloaded. This is probably where all the confusion originated from. I am still in the dark about what the real data should read.
I double checked this andstill got the same specs ad it differs from other info I got from Bryan - I just dunno!....somewhere something is obvious incorrect.

 

[Steve Blair]

Lets for the sake of arguement, take a look at calculated recoil velocity.

Dave,

I agree that bullet mass and muzzle velocity will provide a reasonable recoil approximation, but, to be accurate, the total ejecta mass must be considered. The propellant mass is not insignificant nor is the reaction jet when the projectile leaves the muzzle. Propellant gas velocity is often more than 2X projectile velocity and MV2/2 is driven by velocity. Another aspect is the projectile acceleration rate and the effect on perceived recoil. Propellant burning rates, time spent at max pressure and inertial mass all must be factored for a correct assessment.

All that said, when I was experimenting with muzzle brakes, I found that the easiest way to characterize recoil was to employ a high sampling rate load cell between the butt and the firing fixture and leave all the calculation aside. What we saw was that total recoil could be similar but the energy distribution under the curve greatly affected perceived recoil.

 

[dnirode]

Steve,
Could not agree with you more and would even offer that with high powder capacity cartridges (magnums) that the recoil effect from the propellant gas velocity would be even greater than with a more "standard" capacity cartridge like the .308 Winchester.
We could probably start another discussion on comparison of burning rates (faster is short barrels with a sharper recoil and slower with a more gradual push in longer barrels) and make things more interesting but we'll save that one for discussion over a fine bourbon.
It is however the perceived recoil that you referred to that I was wanting to explain to casspir as I didn't want him to miss out on a possible advantage of the heavier bullet in the wind by going with any bullet weight to lessen the recoil. Recoil is a subjective force and is present in all calibers from .22 rimfire on up thru the big magnums. It is probably more a point how the shooter tolerates it than the actual amount. It is an amazing study that continues to interest us isn't it. Enjoyed your points.

Dave N.

 

[JERRYHM]

Casspir,
Found the problem:
The BC you used (0.464) is G1 data, you used the BC as G7 data. That is the cause of the low wind drift numbers.

 

[casspir]

Hey JERRYHM, I knew there was a RAT!!! Thank you. It gives a much clearer and different picture, doesn`t it?

Carl
South Africa