Heavy Bullets for Long Range
A Long Range Competitor Looks at Heavy Bullets
by German A. Salazar
A number of years ago I read an article by Dr. Geoff Kolbe, founder and owner of Border Barrels in Scotland titled "Comments on Long Range Ballistics". Dr. Kolbe’s straightforward assertion in that article was that there is no such thing as a bullet which is too heavy for long-range (prone) shooting. This position runs counter to the widely-held belief that there is a “tipping point” at which the Muzzle Velocity (MV) reduction caused by the heavier bullet will cause it to drift more than a lighter bullet with a higher MV. Dr. Kolbe demonstrated in his article that, for a given cartridge (he used the .308), as long as each bullet is of similar form and is loaded to the same pressure, with a suitable powder, then the heavier (higher BC) bullet will always drift less, regardless of MV.
That article made me a heavy bullet shooter and for many years my long-range rifle was a Model 70 in 30-06 with a 1:8" twist Krieger barrel shooting the 240gr Sierra MK. While the recoil wasn’t for the casual shooter or for the AR15 types, it was very manageable and produced many match-winning scores. Being somewhat experimentally minded, other projects called and the heavy bullet 30-06 fell into disuse a few years ago. More recently I’ve continued along the heavy bullet path by shooting a 6XC with the Berger 115gr 6mm bullet. A 115-grain projectile is just about the heaviest match bullet available for the 6mm bore. Again, it has proven to be an excellent combination; most recently winning the 2008 Arizona Long Range State Championship with a 797-42X at 1000 yards. Whatever the caliber, heavy bullets work.
Berger Bullets has recently developed a new line of non-VLD, standard profile match bullets in various calibers. I felt this was a good opportunity to put Dr. Kolbe’s theory to the test, since Bob Jensen and I have been doing a large amount of pressure/velocity testing lately with the 30-06 in support of another project. Berger’s new line includes 175 grain, 185 grain and 210 grain bullets in .30 caliber, a perfect selection for our project. A new 30"-long, 1:10" twist Bartlein barrel was fitted and chambered by Clark Fay of Raton, New Mexico (Clark's Rifles) and we were back in business. I should note that this barrel has a perfectly standard 30-06 chamber, no special throating for heavy bullets, although that may come later.
After sorting through loads with a few powders, we determined that Hodgdon’s H4350 would produce maximum pressure levels (60,000 psi) at appropriate velocities for the three Berger bullets and a few others we brought along for comparison. We also tried H4831sc but we were unable to reach maximum pressure before reaching the capacity limits of the 30-06 case. There may be other powders that can deliver the pressure and velocity combo we need, but H4350 is a well-proven powder in the 30-06 and was a good choice. We used an Oehler 43 Personal Ballistics Lab, fitted with the appropriate strain gauge on the barrel to measure pressure and velocity. Velocity is measured via an electronic sky-screen-style chronograph, but a special Oehler strain gauge is fitted to the barrel to measure pressure. It's a sophisticated system. All bullets used in this test were moly-coated using the NECO coating system.
Below is a chart showing the six bullets tested, the muzzle velocity attained with each at 60,000 psi chamber pressure, the remaining velocity at 1000 yards, and the calculated wind drift at 1000 yards. 1000-yard velocities and drift numbers are calculated using each manufacturer’s advertised ballistic coefficient. While this may not provide a perfect comparison across brands, it is certainly a valid method for brand-specific comparisons as the same methodology is used to calculate each brand’s BC.
|Bullet||Muzzle Velocity (fps)||1000-Yard Velocity (fps)||Percentage of MV Retained at 1000 Yards||Wind Drift at 1000 Yards (inches)|
|Sierra 190 MK||2820 fps||1472 fps||52.2%||73.0"|
|Sierra 200 MK||2760 fps||1498 fps||54.3%||69.7"|
|Lapua 185 D46||2880 fps||1548 fps||53.8%||67.9"|
|Berger 175||2980 fps||1593 fps||53.5%||66.2"|
|Berger 185||2900 fps||1605 fps||55.3%||63.6"|
|Berger 210||2730 fps||1611 fps||59.0%||59.2"|
Kolbe Was Right -- Heavier Bullets Drift Less
Even a passing glance at this table shows that Dr. Kolbe was right on the money--no surprise there. Comparing either the Bergers or the Sierras, the heaviest bullet of each type exhibit the lowest wind drift at 1000 yards. And this isn't because of major differences in bullet shape. The three Berger bullets all share the same basic form design and the two Sierra bullets are of the same form as each other. Each brand’s BC methodology is internally consistent.
The Muzzle Velocity (MV) shown for each bullet is the highest that we could reach within the 60,000 psi SAAMI limit for the 30-06. Clearly, there are bullet design issues such as bearing surface length which affect pressure to a greater degree than even bullet weight.
As muzzle velocity increases, drag on the bullet increases disproportionately; thus, most of what you gain in MV is quickly lost. Note that the heavier bullets (of each type) had a higher actual remaining velocity at 1000 yards despite starting out slower. The heavier bullets also retained a higher percentage of their initial muzzle velocity. Muzzle velocity is a depreciating asset, not unlike a new car, but BC, like diamonds, is forever.
Should you immediately run out to buy the heaviest bullets available for your caliber of rifle? Not necessarily--we haven’t spoken about accuracy, recoil, or chamber and twist rate suitability for heavier bullets. All of these factors. which must be taken into consideration. However, hopefully you now have a better understanding of the result of bullet choices and are in a position to make a more fully informed decision for your next cartridge/barrel/bullet selection.
German Salazar, Phoenix, AZ
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