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Rocky’s Reloading Room |
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Working Up Loads for a New Gun
One of the joys of a reloader’s life is starting work with a new caliber. It’s also one of the biggest frustrations. With scores of possible powders to choose from, dozens of different bullet weights, styles and brands, several different primers and many other variables such as seating depth, case sizing options and crimp, there are literally millions of possible load combinations. So how does one start? Believe it or not, there’s a system to these things.
Let’s assume from the start that you acquired this new caliber and gun for a selected purpose. It doesn’t matter whether that purpose is general big game hunting, competition target shooting, long-range varmint hunting, an African safari or teaching a youngster to shoot. The process of developing good safe loads is exactly the same. What we’re about to explore ALWAYS works.
Where do we start? Again, let’s make an assumption or two. We’ll say that the gun is in safe, shootable condition with no major problems, and that its scope or sights are properly installed. The first item we need for reloading is a box of fresh factory ammunition. Factory ammo? To reload? Yup.
The very first thing we need is a baseline, a performance standard from which to judge our efforts later. In other words, we have to know what “good” is if we’re going to make something as good or even better. Factory ammo is that standard, and from it we’re going to learn what velocity, accuracy and relative pressure to work toward. Velocity and accuracy are familiar to you, and we’ll explain relative pressure later.
We select factory ammo in the bullet weight we’re most likely to be reloading later. It’s good, fresh, and not some off-brand, loss-leader second-quality stuff. No Mart-Mart super discount stuff. We want first-quality ammo here. OK, off to the range. With a clean bore, good weather and a good rest, we carefully and slowly fire three five-shot groups. (If it’s a mule-kicking belted whammermag, three-shot groups may be easier on your body.) Of course, we shoot over a chronograph and we record the results of every shot. Each group is on a clean, fresh target, and numbered. That’s it for the first trip. You’ll have about 15 fired cases and five factory rounds left over. Keep track of them.
Back at home, you’ll clean the rifle, noting how much powder and bullet fouling are present. Write down those little bits of info, as well as any other things you noticed. For example, does the trigger need improvement, would the scope be better off farther forward or back, does the action cycle easily or does it hang up when ammo is fed from the magazine. You get the idea.
Get out the targets, chronograph data and the box of ammo. Measure the groups, noting the center-to-center size, where the center of the group lies in relation to the aiming point, and whether the group is basically round or is strung out horizontally, vertically or on a diagonal. Note whether group size or shape changes from the first target to last. Write all this info down. No set format or anything, but jot it down. Trust me, you will NOT remember any of this in two years – or two weeks. And it DOES matter when we finally get down to working up loads!
Now record every pertinent bit of chronograph data you can: highest and lowest speeds, extreme spread, average speed, standard deviation, distance to the first screen, etc. Record the data for each group on its respective target. That’s so we can note any changes as the gun heats up or progressively fouls.
Finally, with a quality micrometer, measure the diameter of each case just above the web at the base of the cartridge. (For a detailed look at case measuring, see the article so titled also on this site.) Measure both the unfired and fired cases. If you removed and replaced the cartridges from the factory box in the order in which they were shot, measure them in the same order. Trends again, right? You’re starting to catch on! Record the diameter of the unfired cartridges as well as the average diameter of the cases used to fire each group, as well as an overall average of all 15 fired cases. Again, it’s a good plan to note these numbers on the targets, too. File all the targets and the chronograph tape together.
All this actually takes less time than it takes to describe it, and now we’re finally ready to start reloading. Again, we’ll start with an assumption. It’s necessary to do full-length sizing in this method, so we’ll assume that the die is set up to size the whole case, but not set the shoulder back so as to destroy proper headspace. First, measure the web diameters of several sized cases and record the average diameter. The number should be between the sizes of the unfired factory rounds and that of the fired ones.
It’s time for decisions. What’s the first component to select? Well, what’s the only component that actually touches the intended target? Yup, the bullet. I’m going to say here that we can limit ourselves to two bullet weights. I’ve almost never seen a case where one of two bullet weights wouldn’t do the job. If possible, pick two weights that are about 10% apart. For example, say I’m reloading deer loads for a .308. I’d pick a 150 and a 165-grain bullet. For varmint loads in a .223, I’d pick a 50 and a 55-grain. You get the idea. Ideally, the heavier of the two weights should be the same as the factory ammo we already shot.
The reason for that is: we’ll be working with the heavier bullet first, and we want to be able to directly compare the speeds, groups and case expansion numbers. We start with the heavier bullet for a reason, too. When we’ve worked a load up as far as is prudent, we’ll be able to use the same powder charge as a start point for the lighter bullet. If we had started with the lighter bullet, we could NOT simply use the same maximum load for the heavier bullet. We’d have to drop back an arbitrary amount and shoot many groups working back up. That’s wasteful and dumb.
With the heavier bullet weight selected, now pick a style appropriate to the job to be done and then a manufacturer. Again, just as an example, we’ve picked the 165-grain bullet for the .308. The load is for deer, so a softpoint spitzer is in order, and finally we pick the Hornady #3040. We could have just as equally picked the 165 Ballistic Tip from Nosler or the 165 Game King from Sierra. Now we go to the loading manual for that EXACT bullet. We don’t use Nosler or Sierra load data if we’ve picked the Hornady bullet. Why? Because the major determinant of load performance, especially pressure, is the bullet. Company A’s data is simply not valid for Company B’s bullet, even with bullets of the same weight. It’d take an entire other article to discuss that in detail. For now, just take it as gospel.
OK, we look in the Hornady manual and see that two powders produce the highest velocity for that bullet. That’s an indication that those powders are optimum for that particular cartridge/bullet combination. Now we also look at the charts for the lighter bullet. In this case, the same two powders are also optimum. We can select either one. If only one powder had been good for both, we’d have started with that one.
To double check, we look at the data put out by the powder company. The listed maximum loads are about the same, within a half-grain or so, so we can presume that the data is safe. We now have the bullet and powder selected, and we’ll be using the fired factory cases, so the only component left to select is the primer. If the loading manual lists the primer they used, we’ll use that one. If not, select a standard primer for the cartridge and stick with it for all our tests.
For our first loads, we’ll prime ten of the 15 fired and sized cases. We’ll weigh out a powder charge that’s 10% less than the maximum listed load, and we’ll seat our 165-gr bullets to the same overall length as the factory rounds. Load five rounds and put them in a small plastic bag along with a slip of paper with all the load details on it. Let’s say that the maximum listed load with our selected powder is 44.0 grains. Deduct about 10% and our first load will be at 40.0 grains of powder. We don’t have to be exact with the reduction, and round numbers are easy to deal with. Now load five more rounds half way between our first load and the maximum, or 42.0 grains. Again, bag them with a slip of paper and load data. That’s all we’ll load for now.
At the range, we’ll duplicate everything from the first session as closely as possible. Set up with the same chronograph spacing, same rest, same weather conditions as possible, and so forth. Shoot the start load and carefully note the feed characteristics, action smoothness, apparent recoil, appearance of empty cases and such. Be sure to mark the target with the load data. If everything is normal and the load seems to be a mild one (as it should) repeat with the mid-charge load. Again, note remarks. Store the fired cases in the same bags as you had them. Be sure you keep them separate or your later case expansion measurements will be invalid!
The second load should be noticeably more powerful. Velocity should be higher, the recoil should be heavier, and the impact point on the target may be in a different spot. That’s all fine. But note well if the action is harder to open, if the fired primers appear flat, or if velocity is as high or higher than of the factory rounds. Those are danger signs, and that’s why we only brought those two loads with us this time! For now, we’ll say that neither load shows danger signs.
Back at home, we’ll now record the same things as before, chronograph data, group size and location, pertinent remarks and such. Now here’s the important step: carefully measure and record the case expansion at the same spot on the case as we did before. Record the average diameter of the five cases in each load. What we should see is case expansion that’s less than that of the factory load, and less expansion in the start load as in the mid-level load.
Here are some hypothetical numbers as an example. Let’s say that the unfired factory cases measure .4700” in diameter. After firing, those same rounds measure an average of .4722.” On average then, factory rounds expand just a bit over .002” when fired in that gun. Our start load, which we hoped would develop less pressure than the factory stuff, expanded cases to .4710” and the mid-level load expanded them to .4717” on average. Velocities also showed a parallel. Again hypothetically, we’ll say that factory 165-grain developed 2650 fps, our start load gave 2425 and the mid-level load gave us 2570. Excellent results so far!
Since our mid-level load proved safe, we’ll work up from there, but in smaller increments. I like to use load increments of about 1% of the maximum at this stage. With a maximum published load of 44.0 grains, that would be .44 grains. No measure or scale is that accurate, so .5 grains is fine. We have 15 fired cases, so load three sets of loads with 42.5, 43.0 and 43.5 grains. Keep everything exactly the same as the first loads, varying only the powder charge.
At the range, we again duplicate as many things as possible and record all data. In this series, we note that when we fire the loads with 43.0 grains, the velocity averages 2645 fps. That’s almost identical to the factory loads. When we fire the first shot of the 43.5-grain load, we notice that the bolt lift is sticky, and the velocity hits 2670 fps. We cease firing at that point, because both the bolt lift and the velocity tell us we are entering dangerous territory. We’ll disassemble those last four loads later and recycle the components.
Recording all our data once again, we note that the 43.0-grain load expanded the cases to .4724” and the single fired round of the 43.5-grain load expanded to .4728.” The 43.0-grain load produced nearly identical velocity and expansion as the factory load, so we can assume that it also produces about the same pressure as well. Note that we do not know the actual pounds-per-square-inch produced, nor do we care. All we need to know is the relative pressure. Do our loads produce less, the same or more than factory loads? Because we can assume that factory ammunition is loaded to maximum safe pressures, if our loads don’t exceed those, we can also assume that our loads are safe.
We’ve discovered that in this gun, a load of 43.0 grains of our selected powder duplicates factory velocities and case expansion. That’s the maximum load for this gun with the heavier bullet weight, even though it’s a full grain less than the maximum load in the loading manual. We’ve discovered this important fact with just three trips to the range, and fewer than 25 shots fired. Elegant, no?
At this point, we can move to our lighter bullet. We can usually assume that this lighter bullet will develop lower pressures with the same powder and charge, so it’s OK to skip the preliminary start level loads and work up from our 43.0-grain load in .5-grain increments. That’s the logic behind starting with the heavier bullet. If the published maximum with the lighter bullet is 45.5 grains, we make initial test loads at 43.0, 43.5 and 44.0 grains. Watching velocity and case expansion, we again stop when case expansion gets to .4720” and velocity doesn’t exceed book numbers. We now have maximum loads with two bullet weights and a wealth of other data. Awesome!
We haven’t discussed accuracy yet, but we also have been tracking that, and if one load showed a definite smallest group, we might juggle the load a few tenths to see if that can be improved, as long as we don’t exceed our maximum. We can also make tiny changes in seating depth, or even try a different primer, as long as we change only one thing at a time.
It’s surprising how often the best accuracy occurs at just under the maximum load. That’s one reason why striving for the last possible foot per second is seldom a good idea. Other reasons to stay under maximum include better case life, better feeding and extraction in the gun, and most important, safer loads.
Safe loads are what this all boils down to in the final analysis. Our discussion so far has been a bit technical, a bit esoteric perhaps. But the one thing to always keep firmly in mind is this: every time we pull a trigger, we release pressures that can exceed 60,000 pounds per square inch. That pressure is contained - we hope! – within inches of irreplaceable body parts. A bit of prudence is a good thing! Safe loading!
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