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| Accurate Measurements Are Critical For Precision Reloading One of the keys in assembling accurate handloads is first precision, assembling a load to fit into and realize optimize performance from an individual firearm. A second aspect of this precision is being able to repeat it from one loading session to the next, and from one round of ammunition to the next. It is one thing to find a powder and bullet combination that shoots well in your firearm, but the way the case is reduced dimensionally during sizing and the exact measurements of all parts of the ammunition are a completely different aspect to achieving the ultimate in accuracy. Furthermore, only with the ability to obtain accurate measurements easily and quickly does implementation of this precision become practical. The amount a case expands during firing relative to SAAMI minimum specifications can be important. This tells you how much your ammunition expanded and once you know the dimension, you know precisely how much the case must be sized to keep sizing and shoulder bump to a minimum and still result in smooth, resistance-free chambering and action lockup. The old trial-and-error method of sizing a case neck and watching for the sizing mark on the neck or trying to bump the shoulder back by feel lack any degree of precision for die setting. It is well-known that bullet seating depth is a variable that can have a major impact on a firearm’s grouping ability. However, the way that bullet seating depth is measured is critical. It is important to squarely engage the land bearing point on the bullet with the measuring device rather than on the bullet tip because bullet tips can cause bullet length (and the land-bearing point) to vary many thousandths. While it is important to measure carefully and properly, it helps if it can be done easily in a manner that every round can be gauged quickly if desired. Bullets themselves can vary and measuring the bullet base-to-land bearing point on bullets can be productive if you’re striving for the best accuracy. You can segregate bullets and eliminate those outside your measurement parameters. Case length is another aspect to ammunition uniformity. Being able to measure cases quickly and accurately, with the entire case held squarely in a device is a decided benefit. While there are a number of devices to take all the measurements mentioned above, you can accomplish them all using a single kit from Redding with parts that fit into a die-like body that screws into your reloading press. It is called an Instant Indicator. The thing I like about the unit is that the usual concerns about holding a cartridge or bullet rigidly in the proper position for accurate measurements is completely eliminated with the die body. You do not have to think about vernier scales or add or subtract thousandths because it works with a dial indicator. The whole unit makes bullet and ammo measurements go quickly, accurately, and repeatably. Instructions received with Redding’s Instant Indicator are detailed and describe all the operations, step by step. Since the instructions are so clear and easy to understand, much of the following was taken from that source with some of my own details added. I believe it is the best way to explain what the unit does and how it works. The Instant Indicator consists of a die body with a precision dial indicator mounted at the top. The internal parts consist of a sliding shoulder contactor, a sliding blank contactor, and a pressure spring. It is also supplied with a brass set up gauge and a bore diameter bushing. The shoulder contactor is the part that contacts the cartridge case shoulder at the datum point. The blank contactor is a solid cylindrical blank with precision ground surfaces at each end. The set up gauge is a brass part shaped somewhat like a cartridge case but with a hole through the middle and without a neck. It is identified with a cartridge designation in a recess milled longitudinally into the exterior. The shoulder angle, datum diameter and datum length (DL) of the set up gauge are made to SAAMI minimum chamber specifications. The bore diameter bushing is a standard Redding neck sizing bushing selected at bore diameter that is used to establish the bore diameter contact point. The pressure spring is a compression spring designed to fit the top cap of the shoulder contactor and either end of the blank contactor. It is used to maintain a uniform contact pressure, ensuring consistent indicator readings. There are several functions that your Instant Indicator can perform to help you produce more accurate reloads, faster and easier. By substituting one or two internal parts you can quickly compare headspace, bullet seating depth, bullet uniformity and case length. Headspace To assemble the most accurate handloads possible, it is important to understand the concept of headspace and how it relates to your firearm’s chamber and handloads. Chamber headspace is determined in many different ways, depending on cartridge type, for example rimmed, rimless, rebated, or belted. However, most important to the handloader is the measurement from the base of the case to the datum diameter on the shoulder. The amount of shoulder bump is under the direct control of the careful handloader. This dimension can be matched to any chamber by proper adjustment of the sizing die using the Instant Indicator. This ensures maximum case life and accuracy from your handloads. Specifications established by the Sporting Arms and Ammunition Manufacturers Institute (SAAMI) assure the compatibility of ammunition and firearms from all manufacturers. Included with the Instant Indicator is a cartridge-specific set up gauge, mentioned earlier, that allows you to compare your chamber’s headspace to the SAAMI minimum chamber specification. To calibrate your Instant Indicator to this minimum chamber specification, slide the set up gauge into the shellholder and raise the ram in your press. Loosen the lock screw that retains the dial indicator in your Instant Indicator and raise or lower the dial indicator slightly until the needle is near the 12 o’clock position. Tighten the lock screw on the indicator extension and then rotate the dial indicator face until the zero is aligned with the needle. Now your Instant Indicator is calibrated to reference the SAAMI minimum chamber specification. Now that you have calibrated your indicator to read zero at the minimum chamber dimension, remove the set up gauge and measure several well formed cases that were fired in your rifle. To get a true reading of your chamber, use cases that have been minimally sized or neck sized only and fired at least two or three times. The first firing of commercial ammunition and/or new brass may provide a fired case that is not yet fully formed to represent the datum length of your chamber. If you get a minus dial reading it likely indicates that your chamber is at or near the SAAMI minimum DL dimension and that the first firing of the brass has not yet fully formed to represent your true chamber length. Many handloaders adjust the full length sizing die to make firm contact with the shellholder when the loading press ram is raised to the top of its stroke. While this is an acceptable method of die adjustment for use when sizing cases to be used in multiple firearms, the careful handloader establishes the proper headspace of cartridges to be fired in a particular firearm. Start your sizing die setup by installing the die in your press until it contacts the shellholder when the ram is raised to its uppermost position. Lower the ram and raise (unscrew) the die 1/4 to 1/3 turn. Size several cases and compare their DL dimension to the previous readings you obtained. If the DL dimension of the cases decreased, raise the die an additional 1/4 to 1/3 turn and start with several new fired cases. Most likely, the DL dimension either stayed the same or increased slightly. If so, adjust the sizing die die down a very slight amount and try again. Repeat this process until you observe .002 to .003-inch of shoulder bump for cases to be fired in most firearms. In the previous example, the fired cases that checked .004-inch would read .001 or .002-inch after sizing. Cases to be fired in a semi-auto should have their shoulders bumped .004 to .006-inch. When you have the die adjusted properly, tighten the lock ring to preserve your adjustment. If you still want to use the die with solid contact against the shellholder, it is possible with the Redding Competition Shellholder Set. I have a Shellholder Set for a .30-06-size rim that has five shellholders in .002-inch thickness increments. They are labeled +.002, +.004, +.006, +.008, and +.010. This way, you can use a shellholder that adds the proper thickness so that the sizing die can be adjusted to firmly contact the shellholder. It can be handy if you’re loading for different rifles of the same caliber with different shoulder bump settings. Just record which shellholder is needed to get the desired amount of shoulder bump simply by adjusting the sizing die to firmly contact the shellholder. Bullet Seating Depth To set up the Instant Indicator for checking bullet seating depth, remove the sliding shoulder contactor assembly and unscrew its black knurled cap. Insert the bore diameter bushing and replace the cap. This provides a bore diameter contact on the bullet ogive, allowing you to quickly and acurately compare the bullet seating depth of your loaded rounds. The ideal bullet seating depth for your rifle is one that produces the best accuracy, yet is not too long to function in your rifle’s magazine. Once the ideal seating depth is found, assemble a dummy round without powder or primer and with this seating depth and use the dummy as a reference zero to compare with others. Bullet Uniformity Today’s bullets are very uniform but you may want to check bullet length from base to the contact point on the ogive. For example, if you are changing lots of bullets you may want to check this dimension to see how it varies from the previous lot. Or, if bullets are inadvertently mixed, you may be able to separate them by gauging them. Sometimes it helps to use the measurement to cull bullets that are not all uniform for whatever reason. The center of the set up gauge has been machined similar to the throat area in a typical chamber. This feature allows you to sort bullets for uniformity of the base to ogive dimension. To set up the Instant Indicator for checking bullet uniformity, unscrew the dial indicator and indicator adapter from the indicator body and replace the sliding shoulder contactor with the sliding blank contactor. Insert the set up gauge into the shellholder and place a bullet, point down into the set up gauge. Raise the ram and adjust the dial indicator to the zero position. Now you are all set to check the uniformity of your bullets. They are held squarely for quick and precise measurement. Case Length Cartridge cases may increase in length as they are fired and reloaded. To ensure safe and reliable handloads, their length should be checked each time they are reloaded. To set up the Instant Indicator for checking case length, unscrew the dial indicator and sliding shoulder contactor with the sliding blank contactor. Select a case that is at maximum length or trim a case to maximum length and place it in the shellholder. Raise the ram and adjust the dial indicator to the zero position. Now you can insert cases into the shellholder and quickly and easily determine which ones need trimming. The description of the Instant Indicator is more involved than actually using it. Once you get one and familiarize yourself with the various parts, it is pretty clear how they all work. Using it is far faster than describing how to use it. Once the Instant Indicator is set up for a specific gauging operation you can gauge a lot of cases or bullets in a hurry in a very uniform manner without a lot of tedium often associated with such tasks. Rick Jamison P.O. Box 691 Springfield, OR 97477 All Rights Reserved |
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1089 Starr Road, Cortland, NY 13045 • Phone (607) 753-3331 • FAX (607) 756-8445 |
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