The .223 for Palma Competition
by Germán A. Salazar
Thanks for writing, you've certainly laid out some interesting questions and I hope we can cover them all with sufficient depth.
The .223 for Palma - Wind Drift Ballistics
Your first set of questions concerns using the .223 for Palma shooting (800, 900 and 1000 yards). I was among those who thought that the paper wind drift advantage would be worthwhile and in 2000 I built a rifle for that purpose, in fact I built two of them. It was a great experience - mostly an experience in frustration, actually - and I learned a great deal. What I found mirrors the experience of others with whom I've discussed the topic:
- the .223 is a very finicky cartridge to load accurately,
- we could never get the same degree of elevation control with the .223 that we could with the .308, and
- the theoretical wind drift advantage of the .233 just didn't amount to anything worthwhile in real shooting, especially in light of the increased elevation dispersion.
Let's use your figures for wind drift: you stated that under a certain set of atmospheric conditions, at 1000 yards, the 155.5 gr. Berger would drift 8.2 MOA in a 10 mph cross-wind and the 90 gr. Berger would drift 7.5 MOA in the same conditions. Thus, the .223 has a theoretical 0.7 MOA advantage in this scenario.
Unfortunately, in either case, if we fail to adjust for that 10 mph wind shift we will place our shot well into the adjacent target, right? Really, anyone who misses a 10 mph shift deserves his miss. What we often fail to detect is a 2 mph shift and that's enough to lose a few points quickly. The 2 mph shift is about what can happen on a switchy wind day between making the windage call and actually firing the shot; it's in the range of reality for any shooter and it's what we hope to guard against with some "ballistic insurance" in the form of higher BC.
Therefore, if we look at the difference in these two bullets in a 2 mph wind shift, what we see is that the 0.7 MOA advantage to the .223 is reduced by a factor of 5 and is now merely 0.14 MOA. That is slightly more than a 1/8 moa "advantage" to the .223 when dealing with the magnitude of wind shift (2 mph) that a reasonably good shooter might miss during shot execution. That's less than one click on the sight. Although now and then it might have been the 1/8 MOA that saved a point, given the difficulty of maintaining good elevation with the .223, points will be lost much more frequently than saved by using that cartridge regardless of the slight, theoretical wind drift advantage.
Load Variance in the .223
The simple fact that all long range shooters deal with is that the 10 ring is a lot wider in the middle than it is above and below the X ring. Accordingly, elevation control is the long-range shooter's principal reloading goal. Service rifle shooters and other competitors who shoot at 600 yards or less don't deal with this issue quite as much because elevation control at those distances isn't particularly difficult. However, as the bullet descends from it's trajectory peak on a 1000 yard shot, the angle is much steeper than on a mid-range shot and the effect of any variance in muzzle velocity is very apparent in increased vertical dispersion on the target.
Your comment regarding the greater percentage variance in a .223 for a given charge weight variance is correct, both as a mathematical proposition and as a reflection of the .223's more exacting nature. However, I will assume that any good long-range shooter can control his charge weight variance to 0.05 gr. - certainly some of the newer powder scales claim even closer accuracy than that. At that level of accuracy, although the .308 has the advantage in terms of percentage of charge weight variance, I think we're in a realistically useful area for both cartridges. This assumes a good scale and proper use thereof, otherwise the advantage to the .308 will be significant as you pointed out.
The .223's small case capacity and powder charge, however, are the root of another significant and perhaps insurmountable problem causing elevation dispersion - the primer. Yes, we're back to my favorite topic. Much though we might wish to believe otherwise, primers just aren't as consistent as we want them to be. Their method of manufacture almost guarantees a significant level of variance in their power output. In the next paragraph I'll give you a couple of examples from my primer testing, this was conducted in the 6BR cartridge, a .223 with its smaller capacity would make the variance greater.
The lowest standard deviation (SD) of chamber pressure was 400 psi with a corresponding extreme spread (ES) of pressure of 1,400 psi. The largest SD of pressure was 1,400 psi with a corresponding ES of pressure of 4,100 psi. These were all high quality primers in use by Highpower competitors, not bargain basement off-brand stuff.
Large primers used in the .308 have similar levels of variability; however, the primer's contribution to the total energy in the system is much smaller in the .308 due to its larger powder charge. The result, therefore, is that the .308 suffers less from primer-induced pressure variability and its resulting elevation variability. Think of the primer as an additional powder charge with some variability that you can't control; then think of that as being 5% of the .223's total energy and 2% of the .308's total energy and I think you'll get the idea (those percentages are not scientifically determined, just rough estimates).
This is the reason that many people are interested in small primer .308 cases and why Lapua has recently introduced such a case. It is an attempt to reduce primer-induced pressure variance. However, the small primer in the .308 case can present its own set of problems with marginal ignition in certain circumstances, but that's another discussion and we won't cover that today. In any event, there is no similar way to reduce the effect of primer variability on the .223 and I believe that will always be that cartridge's Achilles' heel for long-range shooting.
New Powders for .223
New, high-energy powders for the .223... That's about like asking if we should pour higher octane gasoline onto the raging fire. More energy and more MV is about the last thing a .223 needs or can use. I don't mean to sound callous or in any way condescending to .223 shooters with these remarks, but frankly there is no group of shooters that I see experience more serious and more frequent problems related to excessive pressure than .223 shooters.
The .223 case has less metal surrounding the primer pocket than any other case used in Highpower shooting; add in the typical .223 shooter's propensity for heavy loads and you get the blown primer pocket failures that we see every week with this cartridge. Going back to your earlier comment about the increased effect of charge variance on pressure in the .223, consider also that the smaller case responds more dramatically to changes in temperature (and absorbs chamber heat more quickly); it's really just a recipe for disaster. I don't mean to completely dismiss the discussion of new powders, but simply putting yet more energy into the .223 case isn't the answer.
A Few Concluding Thoughts on the .223 for Palma Competition
When I shot the .223 with 90 gr. bullets, the highest velocity I could attain with reliably safe chamber pressure in 30" barrels with a long-throat chamber was 2850 fps. Yes, like many others, I was able to make the bullet go a lot faster, but not with safe chamber pressures and it resulted in the type of case failures that are characteristic of excessive pressure and are completely unacceptable to me as a person who places a high value on safety and on the continued ability to use my eyes.
Whether you accept my 2850 fps limitation or not, however, there is truly an almost insignificant difference in practical (2 mph) wind drift between the 80 gr. and 90 gr. bullets used in the .223 and the various .30 caliber bullets used in the .308 at their appropriate MV.
I believe it is the nature of the American competitor to seek a ballistic advantage in rifle competition. Unlike shooters in most other countries, we have always handloaded and have had a large number of bullet makers enticing us with their "new and improved" offerings each year. This usually results in plenty of wasted time as we re-develop loads, and spend our mental energy at the range "testing" rather than competing. In the rest of the world, the Palma/Fullbore cartridge is much more standardized in terms of bullet and powder and the focus remains - rightly - on the shooter's ability to accurately deal with the conditions between muzzle and target.
The .308 is not what I would consider the ideal 1000 yard .30 caliber cartridge; its capacity is a bit too small to allow the MV needed with safe pressures and generally available powders and the neck is a bit too short to allow chasing an eroding throat or using more than a small range of bullet weights. Yes, the .30 caliber cartridge was perfected in 1906 and everything since then is a compromise - but I digress... The point is that if the .308 isn't exactly ideal, the .223 is far worse. Everything that limits the .308 can be said with even greater emphasis with respect to the .223.
The newer long-range and Palma competitor is better served by following the well-worn path than by trying to blaze new trails. Effective wind reading and decision making for long-range shooting is a true art and it takes a very large effort and a huge number of rounds fired at many ranges under many conditions to even begin to master. Working with non-standard ammunition during this learning process is counter-productive at best.
I can recommend nothing better to you for your 40X than to load the Sierra 2155 or 2156 for mid-range shooting and the 2156 for Palma and then to get about the business of understanding what's happening over that 5/8 of a mile between you and the 10 ring - and leave the .223 out of the equation altogether.