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Handloading: Primers and Priming - INACTIVE AT THIS TIME
For many years, the tried and true way to accuracy test powder charge weights was to load test ammuntion in test lots of five, or even ten rounds. I too used to load and test ammo in bigger batches. I would prep cases as required for my intended use, grab a primer and select a bullet. From there, I would find a powder, often one that "I just had on hand". If I didn't have anything close, I would select the powder that delivered highest velocities that came closest to filling the case. Then, I proceeded as many people do: Load these test cartridges at increments of about ½ grain, beginning with the published starting load and going to the top loads listed. I'd often end up with a whole pile of ammo, and spend hours tediously and carefully shooting these and comparing group shapes and sizes.Some folks even went to far as to suggest five shot groups were insufficient to show us the real dispresion data, and we must shoot at least ten rounds of every load, ideally twice. Luckily, our often limited time and usually bleak financial situation didn't permit this much waste.
We would carry all this stuff to the range, and shoot one or two five shot groups at each increment, but it was always a hard way to go, since we often encountered variable conditions if we went at random times. As a result, we found ourselves going early or late, mainly to avoid wind, since we didn't have "mirage" back then, only "heat shimmy". We also didn't use "ranges", we shot at our respective farms and often rotated where we shot to keep the peace.
"Early" had it's own set of problems, not the least of which were the neighbors that became more numerous with eack passing year. We would pack everything the night before and head out before sunup. By the time it was light enough to shoot, we had our targets posted and yardages paced off and our rifles set up on dirt-filled shot bags. We had about an hour before the breeze picked up, after which testing was tough. "Late" wasn't much better, though the neighbors minded it less, we didn't have to be up as early and everything wasn't soaking wet with dew. We still had only an hour or so from the time the wind laid down until it was too a dark to shoot.
Not only has the aggravation of loading and testing mass quantities of ammunition excessively tedious (for us and the neighbors), but this time-honored approach is fraught with problems:
So, it would certainly seem worthwhile to find a better way if we can. Do better ways exist? Yes.
In the mid-1990's, I discovered the "Ladder Method", developed by Creighton Audette (AFAIK). The ladder method is geared toward finding a stable load in which minor variations have minimal effect. This is an overview of the Ladder Method.
As you can see at the link above, the Ladder Method essentially helps one find a spot at which we can add additional increments of powder without seeing a vertical change in impact points. Finding this "sweet spot" and using a charge weight from someplace in the center of it makes the load relatively insensitive to minor variations in things that cause velocity variations.
Minor changes in primer ignition, bullet weight, neck tension, case capacity, barrel temperature, ambient (ammo) temperature, etc. are often about the same thing as a charge variation when it comes to changing the dynamic. If we find a place that is resistant to reaction from minor charge weight variations, we will also resist the point of impact change due to minor velocity variations caused by any number of other factors.
As we continue to bring the charge weights up by increment after increment, we will see a spot where the point of impact quits climbing with the charge weight increases. This is where we'll want to be.
Even this much more efficient Ladder Method presents it's own problems to the average shooter with the average rifle. The main downsides to this otherwise great method are:
Even with these problems, it is STILL a far better than the old way, ever if we did re-shoot results once or twice.
Is there a method that is better suited to average shooters with average rifles? Yes, Dan Newberry's "Optimum Charge Weight" ("OCW") method of analysis.
A few years ago, I had found out that Dan Newberry had developed a way to evaluate three or five shot groups in a method similar to the Ladder Method, but which took away the critical importance of each individual shot.
Dan (Green788) operates a great handloading site (PracticalRiflery), where he discusses this and helps shooters interpret their test results and rifle accuracy in general. Dan has also had a great site online that went into great detail on his "OCW" method, but has had hosting problems and is rebuilding the site in a new location: OptimumChargeWeight
Dan’s method gives us an alternate method that has the advantages of the Ladder Method, but is enhanced by the use of multi-shot groups to average our results for us. Even if our rifle will only deliver 3” groups, we can still enjoy the benefits of a more streamlined process than shooting group after group and looking only at size.
We are not necessarily looking for that perfect and microscopic group, which is often just a fluke anyway. We are looking for *stability*. We really want a load that shoots well, and shoots the same, even with a little component variation, temperature change, barrel fouling and similar things that slightly affect the dynamic.
Putting "OCW" into practice, we again look for a spot in our charge weight progression that provides stability in the sense that minor changes in charge weight do not show on target. This point is often referred to as “the node”, where vibrations produced during firing are conducive to consistent accuracy.
The more detailed discussion related to understanding (well, as much as anyone understands) this "vibration node" will have to take place elsewhere, but suffice it to say that we will often/usually encounter two distinct nodes where accuracy and stability are very consistent. We will usually see a “low node”, typically well below our desired velocity, and then a second “high node”, which will be near maximum velocity.
To find our own optimum load, we’ll need to find a place to start. A good reloading manual is probably best, and several reloading manuals will provide a better balance of information.
We all see people online list their favorite load. While this can be helpful to a point, there are so many rifle and component variations out there that simply loading what one sees or is told about is clearly insanity, and quite likely not our own best load even if it does seem safe. If we are loading for an oddball that isn’t in the manual, or we otherwise feel that we must "back into it" somehow, we would want to back the load down about 10%.
We can always load single rounds at our chosen intervals and work our way back up, using utmost caution and watching for signs of unacceptable pressures. This will quickly and efficiently give us an idea of our maximum load without jumping right to it and potentially being hurt or damaging our rifle. Once we find our pressure ceiling, it is a simple matter to find a series of increments to bring us back up to just below this point, and safely locate our sweet spot.
Every cartridge can be surprisingly unique. While we can sometimes find satisfactory performance with one powder in several cartridges, or one powder with several bullet weights, this is more often the exception than the rule. We need to decide early on if we want one or more compromises, or if we want optimum performance in a specific situation. If we do decide to use a powder we have on hand and we recognize now that it may not be optimum, we can still proceed if we are able to find a safe starting point. We can still effectively use the OCW method to select a compromise load and it will help us make the best of things.
Since my normal perspective is to try to achieve match quality accuracy and maximum long range performance, I will gear this discussion toward finding the ideal powder and optimum performance in one cartridge with one bullet weight.
OK, let’s go to a loading manual and get started on picking a powder. We’ll go to the section for our subject cartridge, then to the page with our desired bullet weight.
The very first thing we notice is that there are a dozen powders listed as being "OK" to use with this cartridge and bullet weight. You may find it surprising, but I would submit that while most of the powders you see will work, most listed are not at all appropriate. They will be either too fast, as evidenced by low charge weights and low velocities, or, they will be too slow, identifiable by excessive bulk and low velocities.
How can this be? Why should they even bother to list powders that can be used, but don't perform well?
Several factors enter into this:
So, faced with so many possible powders with so few truly suitable choices, how DO we efficiently pick “the” powder we could expect to deliver good performance? Two relatively simple ways immediately come to mind:
First, we can learn from others. If there is a popular cartridge that *everyone* is having *great* results with one certain bullet weight and one certain powder, why would we waste out time and money trying to reinvent the wheel? Two good examples of this are the .308, with 155 to 175 grain bullets and Varget, and another is the .260 Remington with 140 grain bullets using H-4350. These are but a few examples we'll find. We will always want to back down the charge weight and find our own “node”, but at least we have a sense of what will work.
Then, on the other side of the coin, let’s say we find ourselves in largely uncharted territory with a cartridge that few people really experiment with. What then? We can still go to the manual and quickly weed out the poorly suited powders and look hard at what’s left.
I look for a powder that delivers best velocity at a loading density of 95 to 100%. This is almost always the single best powder for this application.
Powders that reach high velocities at lower loading densities are usually too fast for the application. This will normally render them too sensitive to minor changes for best performance. While it may seem more economical and tempting to use these overly fast powders and load to 2,900 feet per second with 40.0 grains of powder when it might take 44.0 grains of another powder will deliver the same thing, it is often false economy.
Surprising? OK, lets lend this huge 10% charge weight savings a little perspective:
At $20.00 per pound, we just saved $2.00 – great, and this 10% number sounds BIG. If we got 175 loads from a pound (7,000/40 grains), we just saved 1.1¢ per shot, or almost a quarter a box.
Meantime, if we can actually load our case 10 times, we’re killing a nickel’s worth of case life every time we pull the trigger. We pop a primer that costs us 2.5¢ to burn 11¢ worth of powder. We send a bullet that often costs 15¢ to 30¢, call it 20¢.
Our net cost to shoot that round was 38.5¢ and the 1.1¢ we've saved is actually 3%, not the apparent 10% we saw on just the powder. If one bullet goes out of the group, what does that actually cost us? 20 or 30¢? A distant varmint or game animal? A hunting trip? A rifle match? I’ve lost a place by one point or one 'X' at several rifle matches, which quite literally IS one bullet out of the group. YMMV, but personally speaking, I’ll pay 3% per round more to keep them all in the group.
Put another way, I would suggest that we are already saving 60% or more on loading our own versus buying factory ammo. Why squeeze it even more at the expense of our ultimate satisfaction and success?
Powders that are too slow have their own difficulties. One of the most obvious is that they usually do not become consistent until we are near top pressures and ignition becomes "crisp". With very heavy bullets, pressures rise more quickly and this may never be an issue. With lighter or even mid-weight bullets, we may not be able to get enough powder behind it, or enough initial resistance for the load to ever fully stabilize.
While I’m not especially adverse to compressed charges, I find that unless we’re using extremely heavy bullets for the caliber, most compressed loads are compressed because the powder is too slow for the application. Light compression is often fine, but when we talk about 105% or greater loading densities, we start to see that slightly faster powder will usually deliver more consistent performance. There are also the peripheral issues of bullets creeping forward in the case neck over time, bullet base damage and ogive damage for excessive seating pressure. We can reduce charge charge volume and subsequent compression by using a drop tube, but this adds yet another step to an already tedious process.
Another way to evaluate and verify that the proposed powder may be one of our best choices is when we look at surrounding bullet weights. If the same powder is listed for slightly lighter or for slightly heavier bullets, and shows reasonable velocities and loading densities, it is a very good chance it will do well for our use. Conversely, if we look at the next bullet weight heavier, and don’t see that powder listed, or it doesn’t compare well with other choices, it may be too fast for what we’re doing. Same if we look at data for a lighter bullet and if the powder we propose to use is not listed or does not perform reasonably well, it is probably a little slow for us. Some judgement and analysis is needed here, but patterns will emerge as we spend more time poring over the manuals looking at things like this.
Now, we’ve selected a powder, what’s next?
We will want to define our increments and load some test rounds. I generally use an increment that is roughly equal to 1% of the total charge weight. For a .223 with an average charge weight of 25.0 grains, 0.2 to 0.3 grains is a good increment. A .308 with an average charge weight of 44.0 grains, 0.4 or 0.5 would be a good choice.
Some folks suggest finer increments, but I’d suggest not. First, finer increments mean more test rounds, which really begins to defeat our purpose of streamlining the operation. Next consideration, and more important, is that if a cartridge/bullet/powder combination is so sensitive to charge weight variations that we can actually see the difference in increments of less than 1%, we’ve probably using the wrong powder anyway. Excessive sensitivity here likely means that any variation introduced elsewhere will destabilize the load.
Unless past experience suggests otherwise, I generally start with the starting load listed in the manual. If the rifle and load is dissimilar to anything use previously, I will often load one round of the first increment, and one round of the second, to allow two sighters/foulers to put the groups where I want them. This also allows me to use the single rounds for the first increment or two to be sure that I am not somehow already into high pressures and make whatever adjustments I wish. Only one round is needed for the two lowest charges, because I don’t care how the first increment groups, I won’t use it anyway. Why waste my time and components to even try to shoot a group with a load I already know will be of substandard velocity?
The next increments will be loaded in quantities of 3, and I will often load a total of 7 increments. Two singles, then five three shots groups, for a total of 17 test rounds. If I have a zeroed rifle and/or I have used similar loads in it, I’ll usually forego the first two sighters and simply load 15 rounds (five 3-shot groups).
Next stop is the range. Because shooter fatigue definitely has an effect on our results, we'll need to consider this in our approach. Environmental factors can play into it too, like increasing winds, changing mirage or sunlight conditions, and we must be careful not to skew our results. For example, if mirage picks up as we’re testing, our last groups may displace vertically and/or get bigger. If we begin to suffer eyestrain, our groups will get bigger.
The way I try to minimize this effect is to shoot “round robin” style. I will shoot first my two sighters on a separate target, then put the first shot of my test group on the first bullseye of my test target. I fire the first shot of my second group next, on the second bull, then the third shot on the third bull, etc., until I have fired one test shot from each increment onto each respective bull. I begin again; fire shot #2 of test increment #1 on bull #1, then shot #2 of increment #2, etc., until I fire all of the second shots of the series onto each bull. I repeat with the last shots. Note that I will watch pressures as I go, and will not finish any increment or shoot any of the increment above it if I encounter excessive pressures.
I evaluate the targets and while I do look for good groups, I am much more interested in where the group centers land on the vertical plane. I would note that some rifles will not show enough vertical variation for this sort of testing at 100 yards, and must be taken to 200 or beyond to show these test results clearly. Velocity is important, but this is also directly related to accuracy potential, and less accurate rifles will need greater distances due to a lack of "definition" in group position on target. 2,900 feet per second is probably a good cutoff point, where we would begin to struggle to see enough vertical change at only 100 yards to make a decision. 3,400 feet per second begins to get tough to evalaute at 200, and we may need to move back to 300.
A chronograph should be used if available, to monitor velocities. Shooting "round robin" will make it very difficult to keep track of extreme spread and standard deviation, so we'll look at this later. If we do see wide velocity variations, we are probably using the wrong powder or the wrong primer. If the load seems to deliver otherwise good performance and good short range accuracy, it's likely the primer.
Groups will usually move up or down as we incrementally change charge weights, and I look for a point at which a couple groups land at the same elevation on target. This indicates a point at which I can vary the powder charge (or introduce another variable) and the bullet will still stay on the group. When we are in the center of the node, it is likely that I can load three cartridges at three adjacent increments and see every one of them land in the same group. This is what I mean by “stability”.
Dan Newberry has discovered an odd phenomenon that he calls a "scatter group" that often occurs as we enter our upper node. I have seen this as well, but it may not be obvious. In the target below, the "scatter group" would seem to be #4-2. At .285" center to center, it may be hard to call it "scattered", but we might note that the first group was one hole and one I know I let go poorly, and the group just after it was only .191" center to center.
This example is a recent string of 100 yard test groups with a .260 Remington, using H4350 and Lapua 139 Scenars:
I pulled the first shot in group #1 (load #4-1), but even at that, the groups was still .357” center to center, and as we can see, any of the groups would be acceptable in a field rifle. The critical thing to notice is that until we reached the last increments, the group centers drifted downwards and eventually stabilized at the bottom edge of the block. The next increment up (#4-5) landed in the same place, but pressure was too high and the group was not completed. Because barrel temperatures are sometimes high, I don’t like to skirt high pressures, so I also abandoned load #4-4 and went with load # 4-3.
Note that in 13 shots, I had found a satisfactory and stable load for this rifle/component combination. This is the efficiency that allows us to avoid spending too much time load testing and more time shooting for the reasons we like to shoot.
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