.30 Caliber Bullet Questions
by Germán A. Salazar
Hi Germán,
I have some questions regarding .30 caliber bullets for Long-Range and Mid-Range.
Currently I'm shooting the Berger 185gr LRBT for Palma in front of 44 gr. of Varget in a 32" 1:11.25" twist barrel; great bullet however it is pricey. For 1000 yards I've tried the 7mm Berger 180 gr. Hybrids the last two years at Perry in my .280 and I didn't notice any drastic improvement over the 175gr Sierra MatchKing. So for Palma shooting, is there any big noticeable difference between the Berger 185gr LRBT vs. say the Sierra 190gr SMK that you have noticed? I know on the calculator there is but was wondering what you've noticed real world. I'm leery about trying the .30 caliber Hybrids because for the additional cost, I want to see a noticeable difference. I was figuring that if I can push the Sierra 190 around the 2700fps mark that I'm getting from the Berger 185 then might as well shoot the 190.
When shooting mid-range, I shot the Palma rifle this year as my .243 was down needing a new barrel. I was shooting either 43 gr. or 45 gr. of Varget behind a 175 gr. Sierra MatchKing. For mid-range, is the 175 gr. SMK probably my best bet or would I be better served with a 155 gr. or 190 gr. SMK? The place I shoot mid-range is fairly sheltered. The largest change a person ever has to make due to wind is 0.5 MOA.
After reading about you trying F-Class I shot double at the state LR match. 2x1000 sling and a 2x1000 F-Class. Will say the small F-Class target was challenging but for me there just seemed to be something missing. However will say when I get to the point I can't see anymore (I'm only 34) I'll do it full time. Nice thing about F-Class though, is it's easy for my girlfriend to shoot and lets me bring her along to matches until she gets more practiced up and use to sling and irons.
Any advice or opinions would be appreciated. Hope the shoulder is coming along well.
Thanks
Shawn
Hi Shawn,
You've put a lot of good questions into your letter; I'll do my best to give you my thoughts on them. Let's begin with the comparison of the Berger 185 LRBT with the Sierra 190 MatchKing. I think this is a great comparison as it presents a clear contrast between two styles of bullet design. Both bullets are of conventional form: tangent ogive, relatively long boat tail, and are intended for similar uses, so the comparison is apt. I'll use the data in the first edition of Bryan Litz's book Applied Ballistics for Long Range Shooting for the dimensions quoted below.
The Sierra 190 has a 7 caliber radius ogive, similar to most of the Sierra MatchKing line (excepting newer designs like the 155 gr. #2156 and a few others). This radius and the overall design derives from the Frankford Arsenal 172 gr. match bullet that was loaded into .30-06 and .308 match ammunition by Frankford Arsenal and Lake City for decades. Compared to many modern designs, this is a relatively blunt nose shape and it results in a long bearing surface of 0.393". The length of the bullet is 1.353" and the G7 ballistic coefficient (BCg7) is 0.270. What does this mean in practical terms?
The Sierra's design results in a bullet that is very accurate and very easy to stabilize. The long bearing surface is always an accuracy enhancer (think of a .38 wadcutter for a moment - it's all bearing surface) and the bullet is shorter for its weight than the more modern designs. That means it will be easier to stabilize in a slower twist, such as a 1:12" twist, than a longer bullet like a Berger 190 VLD (1.386"). This becomes more of a concern as temperature drops and the marginally stable bullet becomes marginally unstable. Of course, the best insurance against this is a slightly faster twist barrel such as you have, or the 1:11" twist that I use. So the Sierra 190 is a stable, accurate bullet, able to be fired in any commonly encountered barrel twist - what are the negative aspects of this older design?
If you compare seating depth to the lands for two bullets of the same weight, one longer than the other (shorter bearing surface, longer nose) the shorter bullet will have to be seated deeper into the case to obtain the same relationship to the lands (jump or jam). Therefore, the Sierra 190 will end up deeper in the case than the Berger 185 and will consume some of the available powder capacity. Unfortunately, the Sierra could really use that capacity to good effect for long-range shooting. The usual solution is to have a chamber with a longer throat, whether as part of the original chambering job or done with a throating reamer at some other time. My .308 reamer has a 0.114" freebore dimension and that is ideal for the Sierra 190 (that's no coincidence). I can still seat 175 gr. bullets into the lands, but 155 gr. bullets will have a fairly big jump. That's no real concern to me because I generally don't shoot any .30 caliber bullet lighter than 175 gr.
The second, and fairly obvious, disadvantage of the blunter 7 ogive design like the Sierra 190 is that it has a lower BC (0.270 BCg7) than a bullet with a longer ogive, like the 9.13 ogive of the Berger 185 LRBT (0.283 BCg7). In order to increase the BC of a bullet of a given weight and caliber, you have to make it longer. You do that by making the nose longer (larger radius ogive) and in some instances by increasing the length of the boat tail. This is kind of like pulling taffy. When you do that, the bearing surface necessarily gets shorter - after all, that extra length had to come from somewhere. Compare, for a moment, the Berger 185 LRBT with the Lapua 185 D46, a very traditional design. The Berger's bearing surface is 0.360" and it is 1.353" long; the Lapua D46 has a bearing surface of 0.408" and it is 1.308" long. As bearing surface is reduced, tuning factors such as seating depth and barrel twist become more critical.
From a bullet designer's standpoint, as you stretch the bullet, the center of pressure on the bullet moves forward, further from the center of gravity. This kind of bullet is a more delicate balancing job for the designer if he wishes to maintain a very high level of accuracy - which, of course, is the ultimate goal. However, Berger has done an excellent job of meeting that challenge in design and manufacturing so we need not concern ourselves with that. To the extent that a faster twist barrel is more suited to such bullets, that can be taken care of at any time with an appropriate barrel; thus we are left with a BC vs. cost trade-off; well, sort of...
Increasing the BC of each bullet model appears to be Berger's goal in recent years and Sierra has followed that lead, although to a lesser extent. I can appreciate the value of reduced wind drift as much as anyone, but I believe that many shooters, particularly those at the intermediate level (Expert and Master in the US) tend to over-value high BC in comparison to other elements of a match-winning performance. To state the obvious, there is no bullet with a high enough BC to allow a shooter to ignore wind changes on a windy day with frequent speed and direction changes. You must know how to respond to those changes and if you don't, then there is no hope of victory (although there is always the opportunity to learn). Conversely, in a low wind environment, such as your home range (you stated that windage changes greater than 1/2 MOA are rare) the high BC bullet has no particular value over a more traditional design.
As a general rule, whether from the .308 or the .30-06, I shoot the Sierra 190 for most of my mid-range matches and the balance are fired with a variety of other traditional design bullets such as the Sierra 180 MK, the Lapua 185 D46 FMJ, Winchester 190 match bullet and a few others. I'm a pretty good scrounger and over the past few years I've managed to buy over 15,000 of these bullets at prices ranging from $15/100 to $18/100. Yes, there's plenty of them out there gathering dust on your fellow shooters' shelves and many are willing to sell. At those prices, there's no way I'm not going to shoot them; in fact, it costs me less to shoot a .30 caliber than a 6mm.
Does shooting these bullets relegate me to mid-pack finishing positions? No!!! In fact, here in Phoenix, where we have incredibly competitive prone matches almost every week of the year, I manage to win a significant percentage of them, and rarely finish out of the top three. The same has been true during my recent excursion into F-TR. Using those old-style bullets for many, many years has been a significant factor in the development of my wind reading skills and at this point, I believe that I am not at a disadvantage as to wind reading at any match in which I compete - and that, more than any bullet, is the key to winning a match. Your equipment must be first rate, your shooting skills nearly perfect and then, you will have the opportunity to test your wind reading skills against the other top shooters and that is the sole factor that decides the finishing order at a big match.
I will add one strong caveat to this discussion, however. It is very difficult to find a safe load with the Sierra 190 in a .308 case that will keep the bullet over 1.2 mach at 1000 yards. This isn't a problem with the .30-06, of course. To maintain that velocity level with the Sierra 190, the .308 will need a long throat and careful powder selection. VihtaVuori N550 is a good choice but it has become very scarce in the US over the past few years. My usual Sierra 190 load of IMR 4064 (MV 2640 fps), while absolutely perfect at 600 yards, is not suitable for 1000 yards for this reason. Accordingly, I only shoot a .308 at 1000 yards with a high BC Berger bullet and only as part of a Palma match. In other matches I shoot the .30-06 or the 6XC. Note that I said "safe load"; there are many unsafe loads being fired, but I have done enough instrumented load testing to stay clear of those. When I say safe, I mean under SAAMI maximum allowable pressure. The shorter bearing surface of the higher BC bullets reduces in-bore friction, allowing a slight increase in powder charge over a traditional bullet design of equal weight. The resulting higher muzzle velocity, combined with the higher BC allows the Berger to remain above 1.2 mach at 1000 yards from the .308 case.
You might ask, then, if there is ever a time when I think the more expensive, higher BC bullets are worth the cost and the additional tuning effort. Yes, there is. For me, that time is when we hold our big championship matches, namely the Arizona Long-Range Championship, the Arizona Palma Championship and the Berger Bullets SW Long-Range Nationals. At the end of 2011, I won the F-TR category in the two Arizona championships using Berger 175 LRBT and 185 LRBT bullets. The margin of victory in the Palma championship was two points after three days of shooting - that's when they pay off. When the competition is highly skilled and the match is of significance, the additional cost for the additional performance is well justified because the higher BC will save you a point once or twice over the course of the aggregate and that's what you'll need. At other times, save a bit of money, shoot more and develop your wind reading skills. Above all, spend some of the savings on gas and get to a windier range! Best of luck to you,
Germán
