In the above drawings depicting bullet run-out, if you have worked up a good load,
(a) will give groups under 1/2 inch in most cases,
(b) will give groups under 1 inch in most cases and
(c) will give groups between 1 1/2 inches - 2 1/2 inches.
Determining or Diagnostic For Bullet Run-Out.
The above conditions will go unnoticed by most reloaders because you have to check bullet run-out 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.
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 Run Out Correction.
Bullet run-out 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 run-out which should be less than .002".
Note: If you are working with new unfired brass do not try to take accurate run-out measurements other than bullet run-out as brass needs fire formed one time to give consistent true readings.
a. All cases that have more than .002" neck run-out should be set aside and checked for case neck thickness, if this is the problem the necks will have to be turned and trued.
b. If your run-out 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. Lee standard dies have the tightest tolerance that I know of without going to a high dollar competition die.
c. 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,
and beyond .002 trash can.
2. Trimming, Chamfering and Deburring.
The next very important step with the cartridge case to minimize bullet run-out is trimming, chamfering and deburring.
a. 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 run-out.
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 cause bullet run-out.
b. 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 run-out.
c. Deburring cases is normally done by hand with a hand tool and can lead to some bullet run-out 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.
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. The 3-way cutter
attaches to Trim Pro
and other RCBS case trimmer models.
3. Bullet Seating.
The bullet seating operation and bullet seating dies vary between manufacturer of these dies. I am going to classify bullet seating dies into 2 classes;
a. wobble dies (which is the accepted standard) and
b. bullet guided dies which are classed as (competition dies).
If you have done everything correctly to this point as outlined above, the accuracy you should expect to get is as follows;
a. wobble dies, bullet run-out should be less than .005",
b. competition dies bullet run-out should be less than .003".
a. 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.
b. 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.
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.
2. If you are looking to gain even more accuracy by eliminating bad brass and checking bullet run-out.
I highly recommend the RCBS CaseMaster® Gauging Tool, as this tool will save a lot in otherwise wasted bullets, primers and powder.
3. If your looking to gain the maximum accuracy for your handloads after (a), (b), and (c).
I highly recommend Lee rifle die sets, pacesetter dies for those who need to crimp their ammunition and deluxe rifle die sets for those who do not. Both are very cheap and available.
If you have read and done everything in my rifle reloading accuracy guide and this bullet run-out guide, you will never look at factory ammunition and wonder why it is more accurate than your handloads simply because you will be able to far exceed factory ammunition accuracy with your own reloading press at a much lower cost.
In a recent outing, gathering reloading components, I managed to get a really good deal on some IMR 4831 powder under $13.00 per pound out the door price, found some Remington 100 grain core-lokt .243 bullets 500 for $34.40 shipping was $10.00 so $44.40, found some Remington 9 1/2 primers $1.59 per 100 out the door price.
Of these components I eliminated 15 bullets after weighing them, brass I already had, so final cost of a loaded cartridge for my 26" barreled .243 Winchester rifle was around 20 cents per round, of the 100 that I have shot and group recorded they are yet to break outside of a .4" outside measure group at 100 yards, just $4.00 for 20 rounds of super accurate ammunition.