Centerfire Rifle Cartridge Reloading Bullet Selection:
Rifle bullets have to form a seal with the rifle’s bore. If a strong seal is not achieved, expanding gasses from the ignited powder charge leaks past the bullet, thereby reducing efficiency and accuracy. The bullet must also engage the rifling without excessively fouling the rifle’s bore, and without damaging the bullet, which will also reduce accuracy.
The leade angle is the angle cut by a chambering reamer on the very end of the rifling lands. This allows the bullet to begin its engraving into the lands on a relatively gentle angle.
Rifle bullet caliber is the outside diameter of a bullet that fits the maximum inside diameter of a rifles rifled bore in the rifling grooves, expressed in hundredths or thousandths of an inch and typically written as a decimal fraction.
–.17″ – .20″ – .22″ – .24″ – .25″ – .26″ – .27″
–.28″ – .30″ – .31″ – .32″ – .33″ – .35″ – .37″
–.41″ – .43″ – .45″ & .51″
Here is an in depth Rifle Ballistics Chart for all mentioned calibers.
The interaction between rifle bullet and rifled bore are termed as internal ballistics. The action of the bullet once leaving the rifle barrel is usually referred to as external ballistics.
Bullet Sectional Density:
Bullet sectional density is a mathematical factor expressing the relationship between the weight of the bullet and its cross-sectional area. Sectional density describes a bullet’s length as to its diameter, the higher the number, the longer the bullet. Generally speaking, longer bullet’s of a given diameter (high S.D.) will penetrate deeper than will shorter bullet’s of the same given diameter (low S.D.).
Bullet Ballistic Coefficient:
A ballistic coefficient is the measure of a bullet’s relative ability to overcome air resistance. Each bullet is assigned a numerical value expressing this efficiency. Ballistic coefficient calculations combine both bullet shape and sectional density factors. Higher B.C.s mean flatter trajectories and higher retained energy down-range.
Rifle Cartridge Bullet Reloading:
Today, bullet selection is excellent for reloaders who have or train with a wide diverse rifle shooting battery, varmint rifles, sporting rifles, tactical rifles, big game rifles and target rifles each of which require top notch accuracy and superb bullet performance.
1. Bullet selection determined by rifling twist rate for proper bullet spin. A good rule of thumb is that the heavier and longer a bullet is, the faster the twist rate needs to be to stabilize the bullet in flight, therefore a lighter shorter bullet needs a slower twist rate to give proper bullet spin for correct flight.
2. Bullet selection determined by bullet construction. Today, bullet manufacturers to stay on top of what the shooting public wants, offer bullets with different construction for different uses. A good example of this is the Hornady bullet line up which offers their V-MAX for varmints, SST for deer and larger game animals and the A-MAX for target work all of which are very accurate with high ballistic coeffecients.
How does anyone really know how precise a bullet is? Well short of x-raying the bullet or using a juenke machine you don’t, but you can sort out most bad bullets by weighing them on a very accurate scale.
While bullet manufacturers are very close today of creating perfect precise bullets the occasional bad bullet can be sorted out. Many reloaders still overlook the reloading value of using scales for their accuracy and ease of use for bullet sorting.
When weighing bullets separate them in increments of 1/10 of a grain. The reason for doing this is that the bullets components when assembled can create slight air pockets or antimony differences depending on the bullets construction which will change the bullets overall weight.
Bullet Seating Depth:
Bullet seating depth has a great impact on rifle accuracy, which directly affects maximum cartridge overall length. The bullet seating depth for each individual rifle free-bore area and bullet varies and should be set accordingly.
NOTE; Caution: Do not use this procedure for rifles chambered for weatherby cartridges as these rifles have extremely long throats or free-bore cut into the rifles bore.
Step 1. Insert a bullet into the neck of a unprimed resized case. Do not fully seat the bullet but seat it deep enough that it is gripped fully by the cartridge neck.
Step 2. Using a black magic marker or dykem steel layout blue, color the entire bullet.
Step 3. Insert the case and bullet into the chamber of the firearm and gently start to close the action. Stop as soon as you feel resistance.
Step 4. Remove the cartridge from the chamber, now look at the bullet, it should have well defined marks where the bullet contacted the rifling in the barrel.
Step 5. Continue seating the bullet deeper and chambering the cartridge until you only feel a slight amount of resistance when the bolt is closed completely. There should only be marks left on the bullet from the lands of the barrel.
Step 6. Now take another resized casing and with your bullet seating die set, repeat seating another bullet in the cartridge case to verify that this is your maximum cartridge overall length.
(NOTE) Never start working up a load with a bullet set against the lands in the barrel as this will sky rocket your load pressures.
Step 7. Shorten your cartridge maximum length by .06250″ or 1/16″ this is where you want to start to tune your load for seating depth.
(NOTE) Best overall accuracy, velocity, pressure uniformity and overall bullet performance will usually be obtained with most bullets seated from the barrels lands between .062″ – .005″.
Once you have loaded a round of ammunition for your rifle there is one final step that you can take that helps eliminate fliers before you go to the rifle range and that is checking bullet run-out.
Checking bullet run-out is nothing more than gauging the accuracy of the bullets alignment with the cartridge case. It is this one simple task that can make or break 1 inch groups or tiny 1 hole groups.
Learn more about bullet run-out here.
RCBS CaseMaster® Gauging Tool:
This tool is simplistic in design and easy to use and a must for diagnosing cartridge problems that are not readily seen by the human eye. How the complete cartridge fits in the chamber and throat of the rifle barrel directly affects accuracy. The RCBS CaseMaster® Gauging Tool, measures case neck concentricity, case neck thickness, case length and bullet runout.
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