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Centerfire Rifle Cartridge Reloading Bullet Runout

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bullet runout

Centerfire Rifle Cartridge Reloading: Correcting Bullet Runout:

Bullet runout is the cause of most reloaded rifle cartridge inaccuracies. Most rifle cartridge case and bullet alignment is determined in the resizing die but there are other reasons and situations that will cause excessive bullet runout which are not readily seen with the human eye.

Bullet Runout Depiction:

The below cartridge centerline drawings are slightly exaggerated for viewing and demonstration purposes of bullet runout.
(a) .000″ – .002″ Bullet Runout.
(b) .003″ – .004″ Bullet Runout.
(c) .005″ – .010″ Bullet Runout.

Determining or Diagnostic For Bullet Runout:

The above conditions will go unnoticed by most reloaders because you have to check bullet runout with a accurate run-out gauge. If you go to the range and are consistently frustrated with group size and bullet flyers out of a good group and you have followed the steps in my accuracy guide read on.

Bullet Runout Correction:

Bullet runout correction begins right after the resizing die step of once fired cartridge cases in rifle cartridge reloading.

1. Cartridge Case Resizing:

Once you have resized a once fired cartridge case the next step is to check case-neck runout which should be less than .002″.
Note: If you are working with new unfired brass do not try to take accurate runout measurements other than bullet runout as brass needs fire formed one time to give consistent true readings.

1a. All cases that have more than .002″ neck runout should be set aside and checked for case neck thickness, if this is the problem the necks will have to be turned and trued.

1b. If your runout is consistently more than .002″ and case neck thickness is not the problem you should check to make sure that your resizing die is clean and properly set, if problem still persists a tighter tolerance resizing die should solve the problem.

1c. At this point you will realize that some brass cartridge casings are going to have to be weeded out and not used. With all work done at this point separating process should be as follows:

.000 super accurate,
.001 very accurate,
.002 accurate
and beyond–.002 trash can.

2. Trimming, Chamfering and Deburring:

The next very important step with the cartridge case to minimize bullet runout is trimming, chamfering and deburring.

2a. Trimming:

Trimming cases can be done by many different types of tools but the bottom line is the case mouth has to be cut true to facilitate the bullet seating operation minimizing bullet runout.

Case Full Length Trimming Depiction:

The below drawings are exaggerated for viewing and demonstration purposes of full length trimming.
 (a) Trued Cut.
(b) Angled Bad Cut.

In the above drawings (a) when properly chamfered and deburred should allow proper bullet seating, (b) when chamfered and deburred will not allow the bullet to be seated properly and it will cause bullet runout.

2b. Chamfering:

Chamfering cases is normally done by hand with a hand tool and leads to a lot of bullet run-out problems. Chamfering cases needs to be done exactly the same on each and every case with machine like accuracy.

Case Mouth Chamfering Depiction:

The below drawings are exaggerated for viewing and demonstration purposes of case mouth chamfering.

 (a) Correct.
 (b) Deep.
 (c) Shallow.
 (d) Angled.

In the above drawings (a) properly chamfered should allow proper bullet seating, (b) chamfer to deep and will most likely leave slivers of brass in your rifles chamber causing accuracy problems, (c) chamfer to shallow will most likely shave copper from bullets causing accuracy problems and will cause bullet run-out, (d) angled cut will most definitely cause bullet runout.

2c. Deburring:

Deburring cases is normally done by hand with a hand tool and can lead to some bullet runout problems in certain bullet seating dies. Deburring case necks needs to be done exactly the same on each and every case with machine like accuracy.

Case Neck Deburring Depiction:

The below drawings are exaggerated for viewing and demonstration purposes of case deburring.

 (a) Correct.
 (b) Not Deburred.
 (c) Angled Deburred.

In the above drawings (a) properly deburred will allow proper bullet guide and seating in all dies, (b) not deburred will have some effect on bullet seating in certain dies and will create accuracy problems inside the rifle chamber, (c) angle deburred will have some effect on bullet seating in certain dies and will create accuracy problems inside the rifle chamber.

3. Bullet Seating:

The bullet seating operation and bullet seating dies vary between manufacturer of these dies, I classify bullet seating dies into 2 classes.

3a. Standard reloading dies (which is the accepted standard). These dies will yield bullet runout generally less than .005″. Standard bullet seating dies will seat bullets straight if the bullet is set on top of the piece of brass straight before you slowly lower the press handle to seat the bullet.

3b. Bullet guided dies which are classed as (competition dies). These dies will yield bullet runout generally less than .003″. Competition bullet seating dies have a collar, collet and or guide that automatically guides the bullet into the piece of brass straight reducing the human error factor.

Summary:

1. If your looking to gain a little more consistent accuracy than what you are getting now from your handloads. I highly recommend if you own a RCBS case trimmer, trimmer 2 or trim pro to add the RCBS Trim Pro 3-Way Cutter. Different caliber pilots are available.

 

 

RCBS Trim Pro 3-Way Cutter.

Trims, Chamfers & Deburrs with lathe like accuracy. Its unique 3-blade head trims cases like a standard cutting tool, the inside blades chamfer the case while an outside blade deburrs it. Excellent tool for precise bullet alignment and seating.

My Picks
RCBS 90276 Pro 3-Way Cutter .17 Cal Case Trim Tool
RCBS 90277 Trim Pro 3 Way Cutter, 20 Caliber
RCBS Trim Pro 3-Way Cutter.22 Caliber
RCBS 90279 Trim Pro 3 Way Cutter, 6mm Caliber

RCBS Trim Pro 3-Way Cutter.25 Caliber

RCBS 90282 Trim Pro 3 Way Cutter, 270 Caliber
RCBS Trim Pro 3-Way, 7-mm Cutter
RCBS .30 Caliber 3-Way Pilot/Chamfer
2. If you are looking to gain even more accuracy by eliminating bad cartridge casings and checking bullet runout. I highly recommend the RCBS CaseMaster® Gauging Tool, as this tool will save a lot in otherwise wasted bullets, primers, powder and time.

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.

My Picks
RCBS 90375 Trim Mate Case Prep Center
RCBS 90366 Trim Pro-2 Kit with Spring Load…
RCBS Rangemaster 750 Scale 9v-dc / 110V-AC
3. If you are looking to gain maximum accuracy from your handloads this can only be done with excellent quality competition reloading dies, bullet alignment has to be precise. I highly recommend RCBS competition dies.

RCBS Competition Dies.

Tight machining tolerances of these dies yield maximum concentricity between the die neck and body. The bullet seater die features a micrometer bullet seating head that lets you adjust the seating depth you want in .001″ increments. There is also a handy bullet window machined through the side of the die to allow much easier bullet insertion. Plus a special bullet seating sleeve assures correct bullet alignment before, during and after bullet seating.

Rifle Reloading Equipment Guide

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rifle reloading equipment

The center fire rifle cartridge is a type of rifle ammunition that has a bullet as a projectile that is fired from a breech loading rifle. 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 refereed to as external ballistics.

The components consist of a piece of brass or cartridge case that contains a rifle powder propellant charge, a primer that ignites the powder charge after being struck by the rifles firing pin and a bullet which is expelled out the muzzle end of the breech loading rifles barrel, by means of the expanding gases of the ignited rifle powder.

The center fire rifle cartridge is reloadable with the use of proper reloading equipment and is generally more accurate than factory ammunition when accuracy reloading guidelines are followed.

Rifle Cartridge Case:

Rifle cartridge cases consist of approximately 70% copper and 30% zinc combined metals and is the fundamental reloading component that does not get spent in the firing process of a center fire rifle cartridge. The cartridge casings main function is to seal the chamber area of the rifle barrel preventing high pressure gases from getting past the cartridge case in the chamber. The reason for using brass for the cartridge case is that it will expand readily and make a seal.

Rifle Cartridge Primer:

The center fire rifle cartridge is aptly named because the cartridge ignition source is a primer located in the center of the cartridge casings web. The type of primer used in American manufactured ammunition is boxer, which have an internal anvil and small explosive charge that when struck by a firing pin ignites, the flame travels through the flash hole in the cartridge case web and enters the case body where the main powder charge is then ignited.

Rifle Cartridge Powder:

Modern smokeless powder once ignited produce expanding gases that push the bullet down the rifles bore giving us a certain amount of velocity to our bullet. Modern smokeless powders come in two types, single base nitrocellulose and double base nitrocellulose with the addition of nitroglycerin. Modern smokeless rifle powder have various shapes and they are, extruded or tubular, ball or spherical, round flat flake and diamond flat flake.

Rifle Cartridge Bullet:

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.

Centerfire Rifle Cartridge Reloading Equipment:

When first starting out to reload your own empty rifle cartridge cases, reloading kits are a very good place to start when selecting reloading equipment. Lee offers probably one of the most economical approaches to reloading with a good solid O-frame press in their kit. There are convenient loading tools offered by other manufacturers as well, all are high quality.

Rifle Cartridge Reloading Data:

Once you have selected a reloading kit (more individual parts, below) you will need a source of reliable reloading data. Bullet manufacturers offer some of the best data as they use a multitude of powder, cartridge casings, and primer combinations for their test results.

Great reloading books:

Rifle Cartridge Reloading:

The first step is to clean and inspect the cases, then lube the inside of the cartridge case neck with the case neck brush, and then lube the cases on the exterior with the lube pad.

RCBS Case Lube Kit 

The linked RCBS Case Lube Kit is the best and simplest way to properly clean and lube cases. Included is the case lube pad, a 2-oz. bottle of Case Lube, and an accessory handle with interchangeable Case Neck Brushes for .22 through .30 calibers. Will not harm primers.


Lee Challenger Press 

The “O” frame press by design is one of the strongest. This is by far the most popular style press. The larger than average opening is angled at 30 degrees for maximum hand clearance. The spent primer catcher is effective and the easiest to empty.

In this step you resize and de-prime the cases by threading your resizing die into the press and attaching the shell holder on the ram of your press.

Lee Pacesetter Dies 

The Lee Pacesetter Dies include the exclusive Lee Factory Crimp Die, resizing and de-priming die, conventional bullet seater & roll crimper die, shell holder, powder dipper, load data and storage box.

In this step you check the case length and will need a stainless dial caliper.

Stainless Steel 6″ Dial Caliper

The one linked will deliver unfailing .001″ accuracy for checking cartridge case length, takes inside, outside, and depth measurements. It also includes a protective storage case.

In this step, when necessary, you trim the cases chamfer and deburr.

The Lee Cutter and Lock Stud with Chamfer, linked above, works for all calibers. Trim cases by hand or electrically.


The Lee Case Length Gauge (Pilot) and Shell Holder

A combination set must be ordered for each specific caliber you plan to reload.

In this step you clean the primer pocket of the case.

Lee Primer Pocket Cleaner

The double ended design on the above tool cleans both large and small primer pockets. Primers can be fully seated for better accuracy and safety. (This is included in the above kit with the lock stud and chamfer).

In this step you prime the case with a new primer.

Lee Auto Prime and Shell holder Set

The Lee Auto Prime and Shell Holder Set is the fastest, most accurate priming tool made. You never touch the primers from the box to the shell. It automatically feeds and installs just as fast as you can place shells in the holder. Both large and small trays and 11 of the most popular shell holders.

In this step you weigh out your powder charge and add it to the case.

Lee Perfect Powder Measure, Lee Safety Scale,

We’ve found this to be the most sensitive and safest of all powder scales. The Lee Powder Funnel is also helpful. Using the lee perfect powder measure you throw a charge of powder within a few tenths of a grain and add it to the scale pan then using the powder trickler (below) over the scale pan you finish the charge, then use the powder funnel to add powder to case.


RCBS Powder Trickler

is the easiest way to feed powder to your scale. Turn the small knob and powder trickles into the pan one kernel at a time. Large-capacity reservoir, extra-wide base for stability, and a perfect height for all powder scales.

In this last step you seat the bullet into the case.

Now you remove your resizing die from the press and thread into the press your bullet seating die and seat the bullet into the cartridge case.

Centerfire Rifle Cartridge Reloading Primer Selection:

The centerfire rifle cartridge is aptly named because the cartridge ignition source is a primer located in the center of the cartridge casings web. The type of primer used in American manufactured ammuntion is boxer, which have an internal anvil and small explosive charge that when struck by a firing pin ignites, the flame travels through the flash hole in the cartridge case web and enters the case body where the main powder charge is then ignited.

The two standard primer sizes for metallic centerfire rifle cartridges are small rifle which are .175″ diameter and large rifle which are .210″ diameter.

Small Rifle Primers (.175″ Diameter):
Small Rifle: Is used for most rifle cartridges requiring a small rifle primer.
Small Rifle Magnum: Is generally used for heavy loads and ball propellants.

Large Rifle Primers (.210″ Diameter):
Large Rifle: Is used for most rifle cartridges requiring a large rifle primer.
Large Rifle Magnum: Is generally used for large case capacity rifle cartridges, or when using ball propellants.

Rifle Cartridge Primer Reloading:
Primers directly affect accuracy more than most people or reloaders realize. The primer is the only component in a cartridge that sets off a chain reaction of events. The first thing that the primer does is start the bullet moving out of the cartridge case and at the same time it ignites the powder charge which in turn pushes the bullet out of the barrel.

Some of the things that can dictate a certain primer usage are extremely hard or soft bullets, bullet seating depth, powder selection by burn rate and or amounts of powder used in the case.

Rifle primers are not the same by any means, there is a difference in the length of time which primers burn. Primers can be selected by heat or pressure range of which there are three fairly distinct and can vary between individual lots produced. Always keep in mind that between primers there can be a hi-lo pressure difference of approximately 12%, when changing primers on a load always start at the start load and work up again.

Just remember when it comes to custom handloading of rifle cartridges there is nothing cast in stone, it is all a matter of trial and error for each individual rifle.

Center-Fire Rifle Cartridge Reloading:

Handloading or reloading is the process of loading rifle cartridges by assembling the individual components; rifle case, rifle primer, rifle powder, and rifle bullet. Handloading or reloading centerfire rifle ammunition is serious business and should never be taken lightly. When done properly and precisely real gains in rifle accuracy can be achieved.
Rifle Cartridge Accuracy:

A. Reloading manual loads and factory ammunition are loaded to fit and function in all guns of a certain caliber. Manufacturers and factories do this with reasonable accuracy, but the ability to customize a cartridge to your firearm leads to excellent accuracy.

B. How you sort and assemble all the cartridge components have major consequences on harmonious ignition and accuracy.

C. As a reloader, you control many of the variables of a cartridge. You select the cartridge case, the primer, the powder, the powder charge, the bullet and most importantly the seating depth of the bullet. You customize the load for your firearm.

Note: This is a critical point to remember, when you are adjusting and working up a load for your rifle, fact is, you are actually tuning and adjusting the barrel vibrations of your rifle.

This Reloading Guide:

The purpose of this short brief guide is to point out the small things in reloading that the average reloader may not be aware of or their importance are overlooked by experienced reloaders. While some of the things described in this guide offer only a small seemingly insignificant gain in accuracy it is a combination of all the little things that add up to a large gain in accurate handloaded rifle ammunition.

Loaded Ammunition Accuracy:

Whether you are an experienced reloader or a beginning reloader, you have no way of telling how accurate your rifle ammunition may be. Bullet run-out in a loaded rifle cartridge for the most part is the reason for most centerfire hunting rifle inaccuracies. I strongly recommend to all rifle ammunition handloaders to purchase the R.C.B.S.

Case Master Gauging Tool, as it will detect accuracy robbing bullet run-out before going to the range. For the reloader it can save valuable time and money by weeding out bad brass before it is loaded with primer, powder and bullet as well.

Next, check out our reloading resources:

About Bullet Runout

Bullet Manufacturers

Powder Manufacturers