December 10, 2020
By Layne Simpson
Part 1: The Accurate Rifle
Part 2: Case Preparation
When loading a large batch of cases, a tray-fed priming tool is a wonderful device. Some designs use reloading press shellholders. An important detail to look for when shopping for one is a close fit between the hole through the shellholder and the guide of the tool for the Small Rifle and Large Rifle priming punches. The punches should also be positioned dead center of the hole in the shellholder. Misalignment can cause the occasional primer to hang up on the edge of the primer pocket of the case rather than entering smoothly. This can damage the primer cup enough to prevent a uniform fit between the bottom of the primer and the primer pocket of the case. It can also fracture the priming compound of the primer. This is more of a problem with Small Rifle primers than with Large Rifle primers.
Another option is to follow the lead of benchrest shooters who use the Phase II Priming Tool from Sinclair International. Of single-feed design, its body and shellholders are precision-machined of stainless steel, and rather than a loose fit with the head of a cartridge case, the case is locked into the holder. That keeps a primer perfectly aligned as it is pushed into the pocket of the case.
Equally important, primers are uniformly seated. The tool can be adjusted for seating by depth or by feel. I prefer the latter with just enough pressure on the handle to seat the primer firmly against the bottom of the primer pocket with the same amount of pressure applied to each primer. The primer should be seated slightly below flush with the head of the case. I have been using this Sinclair product for many years and consider it to be the Rolex of priming tools.
Rather than weighing each powder charge, some shooters throw them with Culver-type measures precision-machined by Neil Jones Products and Harrell’s Precision. I have been using one of Neil’s measures since my benchrest shooting days of the 1970s, and it has thrown many thousands of charges with great precision. But like all measures, it is more consistent with fine-granule powders.
When loading a coarse powder, such as H4831, I set the measure to throw a bit below the desired charge into the pan of a balance beam scale, place the pan on the scale, and then use a teaspoon to trickle in powder until the required charge is reached. On a good day my average is four to five charges per minute.
Digital powder dispensers from RCBS, Hornady, and Lyman have become quite popular. While most guarantee charge weight accuracy of plus/minus 0.10 grain, the MatchMaster from RCBS promises 0.04-grain accuracy when set in its “Match” mode. It is a few seconds slower than the “Standard” mode.
In either mode, large and small dispensing tubes speed up the process. Dispense time varies with powder type and charge weight, but both modes are considerably faster than my old single-mode, single-tube machine. For more information, go to RCBS.com, click on “education” then “videos” and scroll all the way to the bottom.
While using several different digital dispensers through the years, I have followed a simple procedure. After every 12 or so dispenses, the charged pan is removed and placed back on the dispenser a couple of times to see if the weight reading is remaining constant. The indicated weight is also occasionally checked against a balance beam scale. One of the early dispensers I used was quite slow, and rather than twiddle my thumbs while the machine was humming away, I would seat a bullet atop the previously charged case.
Some shooters weight-sort match bullets, but they have become so good I seldom do. I do sort them another way. Due to slight dimensional variations in the ogives of bullets of the same caliber and weight from the same manufacturer, their free-travel distances will vary slightly during firing. That can cause increases in velocity spread for variations in vertical bullet dispersion. Measurements taken from the base of the bullet to an arbitrary point on the ogive will sometimes vary by a surprising amount.
Sorting bullets into batches with each batch having the same base-to-ogive dimension is quickly and easily done by using the Sinclair Bullet Sorting Stand. Simply drop a bullet nose-first into the caliber-specific holder and adjust the dial indicator up and down on its support post until it reads close to zero. Then rotate the dial to exact zero and start sorting bullets.
Small paper cups can be used when sorting bullets into groups with the same measurement, and the groups are then kept separate throughout the loading and firing processes. Small Zip-Loc bags work nicely for that. Bryan Litz of Berger Bullets considers this type of sorting to be the most beneficial thing that can be done to mass-produced bullets.
Two types of bulletseating dies are commonly used for preparing precision ammunition. The Wilson straight-line die is a bit slower to use than a seating die in a reloading press, but some believe it seats bullets with less run-out. I believe it is mostly due to differences in the way the two different designs are used. A small arbor press in which the Wilson die is used has no effect on the ability of the die to seat bullets with minimal run-out.
Such is not the case for sleeve-type dies used in a reloading press. Due to dimensional tolerances during manufacture, the rams of some presses don’t precisely align with the threaded top of the press. In addition, considerable looseness exists between threads of dies and those in a reloading press. As a die is being screwed in, it can be wiggled quite a bit from side to side and to and fro. Simply screwing in a die and tightening its lock ring can leave the die even more misaligned with the ram of the press. This can introduce or increase run-out of full-length resized cases and seated bullets.
While the misalignment might not be totally eliminated, it can be minimized. With the ram raised, screw in the die until it contacts the shellholder. Then lower the ram, screw the die in another 1/8 to 1/4 rotation, fully raise the ram, cam it slightly over dead center, and while holding it there, use a wrench or pliers to firmly tighten the lock ring of the die. The die and shellholder of the press should now remain square and in alignment.
If installing a full-length resizing die in that manner pushes case shoulders back too far, back the die away from the shellholder, place one or more steel washers from the hardware store atop the shellholder, and then complete press cam-over and die lock-down. Some handloaders don’t realize that top-of-the-line reloading dies and most presses are designed to handle this without damage. Instructions included with RCBS Gold Medal Match dies recommend doing so, and Redding representatives offer the same advice.
I have owned a Corbin CSP-1 bullet-swaging press for many years and often describe it as what an Abrams tank would be like if it were built by a Swiss watchmaker. A conversion kit included with it is for use with standard 7/8-14 dies. I had never gotten around to trying it for loading cartridges until a friend mentioned using his for turning out match ammunition. Due to precise alignment and fit between its component parts, reloading press-induced bullet run-out in ammunition is a thing of the past. This assumes properly prepped, high-quality cases are used.
How much bullet run-out in precision-loaded ammo is too much? Zero run-out is the goal, but most of us are happy with 0.001 inch or a bit less.
Fit between case and chamber is closest after the case has been fired, and it is best left that way for as long as possible. For this, a neck-sizing die with interchangeable bushings of various sizes is a must-have item.
How much of the neck to be resized is determined by how deeply a bullet is seated into the neck of the case. If the base of the bullet rests adjacent to or beyond the neck-shoulder juncture of the case, the neck is resized as close to the shoulder as possible with a sizing bushing. For example, when a Bart’s 68-grain flatbase bullet is seated for my benchrest rifle in 6mm PPC, its base is 0.240 inch into the 0.280-inch neck of the case, therefore only 0.240 inch or so of the neck is sized. Leaving the rest of the neck at its fired diameter helps to keep the cartridge in proper alignment when chambered.
When cases are new, I start with a neck-sizing bushing 0.001 inch smaller than the neck diameter of the case with a bullet seated, and if velocity spread is not as low as it should be, 0.002-inch and 0.003-inch bushings are tried. That’s for match ammo.
When loading hunting ammo, I start with a 0.002-inch smaller bushing with new cases and go from there if necessary. After a number of firings, slight resistance to bolt closure will tell you it is time to break out the full-length resizing die.
Off-the-shelf dies are reamed to squeeze a case slightly smaller than the SAAMI minimum chamber dimensions for a particular cartridge. They have to be that way in order for cartridges to be usable in chambers reamed to SAAMI dimensions, but in addition to overworking the brass, it eliminates the desired close fit between the case and the chamber of a precision-built rifle.
A custom full-length resizing die from Whidden Gunworks in Nashville, Georgia, is the answer. Send three cases fired in your rifle, and the company will custom-ream a die that squeezes down a case just enough for trouble-free chambering. Those carefully prepared cases will last longer, and their fit with the chamber will remain close.
When it is time to full-length resize, measure several fired cases and then adjust the die to push the shoulder back 0.002 inch. Tools like the RCBS Precision Mic, Hornady Headspace Comparator, Redding Instant Headspace Indicator, and Sinclair Shoulder Bump Gauge make the before and after measurements easy.
Some short-distance benchrest shooters seat bullets in cases to lightly touch the rifling when a round is chambered; others seat for various degrees of rifling engagement; and others prefer a bit of jump. The rifle makes that decision.
My Light Varmint class rifle in 6mm PPC is most accurate with VihtaVuori N133 and Bart’s 68-grain FBHP seated 0.005 inch into the rifling. A GA Precision rifle in 6mm GT I’ve worked with shoots the Berger 105-grain Hybrid Target best with 0.010 inch of engagement. Other rifles prefer to have bullets seated off the rifling, but it is not always about the rifle alone. Different bullets can have different preferences in their relationship with the rifling, and the same goes for different powders. When the Bart’s 68-grain bullet is seated atop Benchmark in my 6mm PPC, it prefers 0.005 inch of jump.
Due to the possibility of a bullet being pulled from its case and powder spilled into the action when a cartridge is chambered and then extracted from the chamber, bullets in ammunition loaded for hunting rifles should never be seated out for even light rifling engagement. I prefer no closer to the rifling than 0.020 inch.
Due to restrictions in magazine length of some factory rifles, bullets have to travel quite a distance prior to engaging the rifling. It is not unusual to see them shoot the smallest groups with bullets of monolithic construction.
The Sinclair Seating Depth Tool and the Hornady Lock-N-Load Overall Length Tool are used to determine the dimension from the head of a cartridge to a point on the ogive of a bullet when the bullet is seated to make light contact with the rifling. I use the Sinclair tool more often because it does not require a modified case during the measuring process. Once bullet-to-rifling contact is made, the Sinclair Insert-Style Bullet Comparator, the Davidson Seating Depth Checker, or the Hornady Lock-N-Load Bullet Comparator is used with a digital caliper to measure from the head of a cartridge to a point on the ogive of the bullet.
Let’s say you are loading the Nosler 105-grain RDF in the 6mm Creedmoor case. The measurement is 2.175 inches and you want that bullet to jump 0.005 inch prior to rifling engagement. The stem of the bulletseating die is adjusted to seat the bullet to a measurement of 2.170 inches. Or if the rifle is more accurate with the bullet seated 0.002 inch into the rifling, the loaded round measurement would be 2.177 inches.
Hollowpoint bullets of the same caliber and weight from the same company vary slightly in length. That makes recording overall cartridge length less accurate than recording the measurement from the head of the cartridge case to a point on the ogive of the bullet.
I began handloading before precision tools became available and have used various other methods to determine when a bullet is seated close to the rifling. One begins with inserting a flatbase bullet nose-first into a case and seating it deeper in small steps until the bolt will close on the “dummy” round with light resistance. A digital caliper is used to measure from the head of the case to the base of the bullet.
Let’s say I am loading the .243 Winchester for my Winchester Model 70 heavy-barrel varmint rifle, and the measurement is 2.156 inches. Regardless of the bullet I will be loading, the distance from the face of its bolt to the beginning of the rifling is 2.156 inches, and that information is recorded for the Model 70. When developing a load for that rifle, I seat a bullet long in a case, push the nose of the bullet firmly into the muzzle of the rifle, and twist it enough to leave a mark around its surface. The bullet is then seated deeper in steps until a digital caliper indicates 2.156 inches as the distance from the head of the cartridge to the mark on the bullet. That tells me the bullet is seated close to the rifling, and experimenting with bullet jump can go from there.
That is not quite as accurate as using a precision tool. Also keep in mind that the distance between the boltface and the rifling will increase due to erosion and should be checked occasionally.
Repeatedly firing and resizing the neck of a case work-hardens it, and the harder it becomes, the more neck tension will vary among a batch of cases. Variations in the amount of tension applied to bullets will cause increases in velocity spread, and that’s not a good thing when a target is small and 1,000 yards away.
Some competitors anneal the necks of cases after each firing, while others do so less frequently. Machines such as the Annealeez, Bench Source, and Anneal-Rite use propane torches, whereas the Annealing Made Perfect unit heats case necks by electrical induction. They control the amount of time heat is applied to the case.
Regardless of which method is used, it is important to remember that allowing anything but the neck and shoulder of a case to become extremely hot can soften a case too far back and firing it can cause damage to the rifle and possibly the shooter. Keeping case necks trimmed to the exact same length also contributes to low velocity spreads.
There you have it: the lowdown on priming, powder charging, and bulletseating, with a focus on some of the excellent tools available to shooters who want to get the most accuracy they can from their handloads.