joeb33050
01-23-2009, 03:02 PM
THE SEARCH FOR CAST BULLET ACCURACY
This first describes a method of achieving reasonable accuracy that I define as reliably repeatable sets of five 5-shot groups averaging less than 2” at 100 yards.
It is not the ONLY recipe, it may not be the BEST recipe, but it is a recipe that will work.
The Steps
The shooter should be familiar with reloading, willing to learn how to cast bullets, and own or be prepared to buy the necessary equipment and to carefully cast, load, shoot and record the results. (Much used reloading and casting equipment is available at various shooting forums or auction sites.) The three editions of the Lyman Cast Bullet Handbooks and any edition of their Reloading Handbook are of great help.
The gun: a commercial non-military bolt-action 30-caliber rifle, such as a recent Savage, Remington, Winchester or Ruger in very good condition. This method explains how to find the innate accuracy that the rifle has; it does not pretend to make a greatly worn or damaged inaccurate rifle shoot well.
With a new rifle, make sure that:
There is no obvious bedding or barrel problem.
Sights are mounted solidly and correctly.
Screws are tight.
New rifle barrels may be "broken in" by the owner. Instructions and opinions of cast bullet barrel break in abound and conflict. I have no opinion, and just shoot any new barrel.
With a used rifle, make sure that:
There is no obvious bedding or barrel problem
Sights are mounted solidly and correctly
There is no damage to the muzzle crown
Screws are tight
The barrel is clean, no copper or other fouling is in there
The sight/s: a telescopic sight of at least 6 power, preferably with an adjustment to eliminate parallax, or, as a more expensive and less desirable alternative, a set of good aperture iron sights.
The caliber: 30/06 Springfield or 308 Winchester
The bullets: Lyman 311299 or 314299, of good quality, gas checked, sized correctly, lubed with a good commercial lubricant.
The powder: IMR 4227. The charge must be appropriate for the cartridge and bullet. Lower velocity loads from the Lyman 48th Reloading Handbook should be used.
The bench rest equipment and technique must be adequate to allow precision shooting.
Meticulous records must be kept of all casting, loading and shooting information.
Some Notes:
The Bullets
Cast the bullets from wheel weights with maybe a little tin added. Visually inspect the bullets, re-cycle the rejects. Weight sort the bullets if you wish.
(The following steps require a Lyman 45 or 450 or 4500 lubrisizer, RCBS or Saeco lubrisizer or Lee Lube and Size kit.)
Seat the gas checks in a separate operation.
Size the bullets to the correct diameter.
Lubricate the bullets with a good commercial lube, such as NRA Alox lube. No homemade lubes!
Fitting the bullets to the gun
The 311299 and 314299 bullets are about 200 grains with bore riding noses. The 314299 bullets are a bit larger than 311299s, the noses are larger in diameter, and, until sized, the base bands are larger.
Both bullet molds today are 2 cavity. Mark the cavities so that you can tell which cavity the bullets came from. There is always a difference in bullet weight and some dimensions from one cavity to the other.
Cast bullets are not round, and dimensions of the as cast nose and base bands show this. I cannot ever recall a bullet with dimensions +/- a tenth, (.0001”), and normally 3 or 4 or more tenths difference is the rule.
Bullet fit
The cartridge should chamber with a bit of resistance.
The bullet should not stick in the chamber when the chambered cartridge is extracted. No de-bulleting!
The base of the bullet should be in the neck, not down inside the case. If just the gas check is below the neck, there’s generally no problem.
The nose of the bullet should be engraved by each land of the rifling.
The forward-most end of the front base band should slightly mash into the origin of the rifling.
Increasing the amount of tin and/or antimony in the alloy yield slightly larger bullets.
Sizing the bullet in a lubrisizer makes the nose bump up larger.
Bigger as-cast to sized differences make the nose larger than smaller differences. Size a .314” to .308” and the nose will bump up more than when sizing from .314” to .312”.
Softer bullet noses bump up more than harder bullet noses.
Bullets with base bands sized to different dimensions may/will have different overall lengths.
Rifle barrel lands at the chamber end wear or erode, so that cartridge overall length increases slightly and slowly as the rifle is shot.
If the cartridge that goes in the gun has a lot of base band below the neck, change something.
If the cartridge goes in the gun, has just the gas check in the case mouth and doesn’t engrave the bullet nose, change something.
If both 314299 cavities make bullets too big, go to the 311299. If the 311299 bullets are too small, either the gun or the mold is incorrect.
If both 311299 cavities make bullets that are too small, go to the 314299. If the 314299 bullets are too big, either the gun or the mold is incorrect.
Reloading
Get a set of good cartridge cases from the same lot, at least with the same headstamp.
Full-length size them. (New cases will shorten when fired. Used cases won’t, much.)
Measure the lengths and trim to the same length. (Same length cases are required for proper case mouth “belling” with the “M” die.)
Chamfer the case mouths in and out. (Lee makes inexpensive tools to chamfer case mouths and trim cases to length.)
Bell the case mouths with a Lyman “M” die in a press.
Prime (Lee makes a great and inexpensive priming tool.) Any large rifle primer will work fine.
Cartridge “lot” size is 35, make a set of 35 cartridges for each trial load. (The set of 120 cases allows loading three lots of 35, with thirteen spares.) Just checking.
Charge the cases with powder.
Lyman 48th Edition Reloading Handbook
“308 Win., 311299 at 200 grains
IMR 4227,19.5 grains starting load to 26 grains maximum load”
Start with 18 grains, and then go up in 1-grain steps to 22 grains
“30/06 Springfield, 311299 at 200 grains
IMR 4227, 21 grains starting load to 29 grains maximum load”
Start with 19 grains, and then go up in 1-grain steps to 24 grains
ALWAYS CHECK A PUBLISHED LOAD TO SEE IF IT MAKES SENSE!!!! BELIEVE NO ONE!!!
Inspect the cases with a flashlight to detect “no powder” and “double charges”.
Seat the bullet to the correct overall length.
Shooting
Shoot only on a day with reasonable weather. No hurricanes or blizzards.
Testing a rifle for accuracy requires a solid bench rest on a sold bench, and a good chair or stool. Use a reasonable front and rear rest. Rests can be bought for prices ranging from OK to crazy. I have used a Hoppe’s front rest as well as home made rests, and they all work well.
The target used must work for the shooter-target types, shapes and styles affect group size.
Push a patch through the barrel.
Get comfortable at the bench.
Shoot 3 foulers, and then two 5-shot groups for record in about 15 minutes. Don’t let the barrel get too hot!
Clean the barrel.
Shoot 3 foulers, and then two 5-shot groups for record in about 15 minutes. Don’t let the barrel get too hot!
Clean the barrel.
Shoot 3 foulers, and then ONE 5-shot group for record in about 10 minutes. Don’t let the barrel get too hot!
Clean the barrel.
You’ve shot five 5-shot groups and 9 foulers for 34 shots. What about the #35 cartridge? If you call a honked shot, you’ll need that #35 cartridge to make the fifth shot in the group.
Recording the data
Write everything down. Write the reloading data down when you reload, and the shooting data on the day you shoot. DON’T WAIT FOR TOMORROW, YOU’LL FORGET SOMETHING!
Write down the powder charge and primer make and lot numbers if you wish and the overall length and bullet # and just everything.
If you pull a shot, honk it out of the group; and if you call it honked before you look through the scope; then take another shot for record. Don’t lie to yourself.
AN ASIDE: WHAT TO DO IF THE RIFLE WILL NOT GROUP IN 2” AT 100 YARDS
I write with limited experience, counting on others for help. “Frank 46” and ”The Nyack Kid” on “Cast Boolits”, “linoww” and “runfiverun” on the CBA forum, John Bischoff, William W."Bill" McGraw, Paul Brasky and Dave Goodrich have helped a great deal. Some of their suggestions are in quotes below.
“Shoot the rifle with a good jacketed bullet load. If the gun and load are capable of at least 1.5" groups at 100 yards, the gun should shoot cast bullets accurately.”
“Check for crown damage or a barrel bulge.” Look at the barrel crown under a good light and a magnifying lens, check for any damage. If there is damage, re-crowning the barrel is fairly simple and may cure the problem.
Push a cleaning rod with a tight patch through the barrel, feeling for any sudden lack of resistance that indicates a bulge in the barrel. If there is a barrel bulge, the rifle may not shoot cast bullets accurately. However, I have seen, been told about and read accounts of bulged barrels shooting accurately.
“Have another, experienced, shooter try your rifle. Sometimes your grip/ forearm rest / butt stock rest can cause problems. I had that shown to me once, much to my chagrin, moving the forearm back two inches on the rest cut my groups by 30%”.
For a gun with a “free-floating barrel, check the gun for interference between the barrel and stock. Use something thicker than a dollar bill, maybe 3 dollar bills.
Take the barreled action out of the stock, inspect both for any signs of interference or rubbing or polishing. If there is a sign of interference, sand the stock. This has to do with interference between the action and the stock
Put cardboard shims, matchbook cover ~ .025”, under the front and rear receiver rings, then put the gun together. This will free-float the barrel. If needed, “glass bed” the action in the stock.
Check the scope screws and action screws to make sure that there is nothing loose. I have never used a torque wrench on action screws, yet.
“Check tightness of scope base screws, and scope ring screws.”
”Set action screws with a torque wrench to the approximate tightness you use. The main screw might like 50 inch-pounds and the rear one somewhere around 35 inch-pounds. The third one, if there be one, might be happiest around 20 inch-pounds. Your rifle WILL be different
from all other rifles.”
“Try a different scope.” I have seen and talked to other shooters who have found that the scope sight is defective, and causes inaccuracy. I have never had an inside-adjustable scope that caused inaccuracy, and cured an outside-adjustable Lyman STS scope of this trait by cleaning the adjustment ring.
I have very seldom reached this point without being able to shoot 5-shot 100 yard group averages under 2”. If the steps listed above will not get the rifle shooting under 2”, I don’t know what to do next.
BACK TO THE SEARCH FOR BETTER ACCURACY
If reliably repeatable sets of five-5 shot groups averaging less than 2” at 100 yards have been achieved, and if better accuracy is desired, here are the steps:
I start with a set of at least 120 cartridge cases of the same lot (or at least with the same headstamp). This allows me to load three sets of 35 cartridges, with 15 extras. I put the not-loaded cases in a plastic bag; these are the first cases loaded the next time. This takes care of rotating the cases so that all are loaded about the same number of times.
When a case neck splits, I find it when processing the cases in my hands, (cleaning the neck, de-priming, cleaning the primer pocket, lubricating the case), when sizing, or when belling the case mouth in a press with the Lyman “M” die. Low resistance when pulling the case over the expander button or pushing it over the “M” die can mean a split neck.
When a case neck splits I anneal the necks of all the cases in the lot.
When primer pockets enlarge such that primers are loose, I’ll throw away the set of cases. I shoot lower velocity cast bullets only, and have never had primer pockets enlarge, nor have I ever had a case head separation.
As described above, cases should be trimmed to a common length, case mouths chamfered in and out, and necks belled after sizing.
These steps may increase accuracy, though I have never seen any convincing data or report that shows that. I always do these because they are inexpensive and easy.
Uniform primer pockets
De-burr flash holes
Clean inside case necks with a bronze or (I use) nylon brush. The brush may be chucked in a drill for more speed.
Clean primer pockets
These next steps have worked for me and are roughly in order of their effectiveness in reducing group sizes. Some or all of these steps should get the rifle to shoot 100 yard average sets of five 5-shot groups between 1.5” and 1”. (Based on the CBA National records over several years, competitors average around 1" over the classes. This means that those who shoot in each of the four classes, all told, average about 1". At the 2008 CBA National Tournament 15 shooters shot in Production Class, in the 100 yard, four group, five-shot match. Of the 15, 4 shooters averaged less than 1”, and 11 shooters averaged over 1”. The 15 shooters averaged 1.224” groups. Averaging 1" with cast bullets is tough.)
Change the powder. I have seen substantial changes in group size averages associated with changes in the powder. For example, Paul Brasky recommends A5744 and IMR4198 in 308 Win. CHECK THE RELOADING MANUAL (S)! (Note that these two and other powders don’t go through powder measures accurately. I dribble and weigh charges of these powders.)
Change the powder charge in .5-grain steps. (Powder charges of IMR 4227 were varied above in 1-grain steps.)
Weight segregate bullets. This step is time consuming, but serves to identify the oddball low or high weight bullet that may be a flier.
Adjust the trigger to reduce pull weight and/or over travel and take-up.
Change the bullet hardness
Change sized bullet diameter
Try another bullet
Use wind flags and learn to shoot in the wind.
These steps may reduce group size below 1” 100 yard 5-shot averages. Many are used by good cast bullet shooters. I have never seen any convincing data that any of these steps reduce group size with cast bullets. However, it is equally true that none of these steps will make groups bigger.
Change the lube. There is a wide variety of lubes used by good CB shooters, reinforcing my belief that “reasonable” lube choice has little or no effect on accuracy. This does not mean that one cannot concoct a lube that adversely affects accuracy. I have done so. Hence “reasonable”.
Vary the number of lube grooves filled
Use “better” cases. In modern jacketed bullet bench rest, “better” cases such as Norma or Lapua are said to be more accurate than domestic cases. Some contend that the same is true with cast bullets.
Change the primer.
Change the powder charge in .1-grain steps. For charges above ~ 15 grains of powder, it is my belief that charges in .5 grain steps are as precise as required. Charges of XX.1 or XX.2 produce no accuracy difference from charges of XX.0. Charges of XX.3 or XX.4 produce no accuracy difference from charges of XX.5. Some contend otherwise, data is sadly lacking.
Weigh and control powder charge weights.
Make the cartridge case length = chamber length -.005”. It has been claimed that minimizing the distance in the rifle chamber from the end of the cartridge case to the end of the chamber will increase accuracy. .005” is frequently mentioned as the safe minimum.
Weight segregate the cases.
Weight segregate the primers.
Weight segregate the gas checks.
Anneal the gas checks.
Turn or inside ream the case necks.
Ream the flash holes to a uniform diameter.
Orient the case in the chamber.
Orient the bullet in the chamber.
Orient the bullet in the case and the case in the chamber.
Try different barrel cleaning methods and frequencies.
Check and improve cartridge concentricity.
Vary OAL by .002"? .005”? .010”?
Shoot bullets in the order cast. Recommended by some single shot rifle shooters.
These steps require some substantial money and/or expertise. Between the steps above and these, and with quite a few bucks spent, it may be possible to reliably shoot 100-yard 5-shot groups averaging below 1”.
Size the case necks in a Redding or Wilson replaceable bushing style neck sizer
Seat the bullets with a precision micrometer adjustable sizing die
Glass bed the rifle action.
Ream the chamber throat.
Get a taper die to match the reamed chamber throat and taper the bullets.
Re-crown the barrel.
Lap the barrel.
Replace the barrel.
This first describes a method of achieving reasonable accuracy that I define as reliably repeatable sets of five 5-shot groups averaging less than 2” at 100 yards.
It is not the ONLY recipe, it may not be the BEST recipe, but it is a recipe that will work.
The Steps
The shooter should be familiar with reloading, willing to learn how to cast bullets, and own or be prepared to buy the necessary equipment and to carefully cast, load, shoot and record the results. (Much used reloading and casting equipment is available at various shooting forums or auction sites.) The three editions of the Lyman Cast Bullet Handbooks and any edition of their Reloading Handbook are of great help.
The gun: a commercial non-military bolt-action 30-caliber rifle, such as a recent Savage, Remington, Winchester or Ruger in very good condition. This method explains how to find the innate accuracy that the rifle has; it does not pretend to make a greatly worn or damaged inaccurate rifle shoot well.
With a new rifle, make sure that:
There is no obvious bedding or barrel problem.
Sights are mounted solidly and correctly.
Screws are tight.
New rifle barrels may be "broken in" by the owner. Instructions and opinions of cast bullet barrel break in abound and conflict. I have no opinion, and just shoot any new barrel.
With a used rifle, make sure that:
There is no obvious bedding or barrel problem
Sights are mounted solidly and correctly
There is no damage to the muzzle crown
Screws are tight
The barrel is clean, no copper or other fouling is in there
The sight/s: a telescopic sight of at least 6 power, preferably with an adjustment to eliminate parallax, or, as a more expensive and less desirable alternative, a set of good aperture iron sights.
The caliber: 30/06 Springfield or 308 Winchester
The bullets: Lyman 311299 or 314299, of good quality, gas checked, sized correctly, lubed with a good commercial lubricant.
The powder: IMR 4227. The charge must be appropriate for the cartridge and bullet. Lower velocity loads from the Lyman 48th Reloading Handbook should be used.
The bench rest equipment and technique must be adequate to allow precision shooting.
Meticulous records must be kept of all casting, loading and shooting information.
Some Notes:
The Bullets
Cast the bullets from wheel weights with maybe a little tin added. Visually inspect the bullets, re-cycle the rejects. Weight sort the bullets if you wish.
(The following steps require a Lyman 45 or 450 or 4500 lubrisizer, RCBS or Saeco lubrisizer or Lee Lube and Size kit.)
Seat the gas checks in a separate operation.
Size the bullets to the correct diameter.
Lubricate the bullets with a good commercial lube, such as NRA Alox lube. No homemade lubes!
Fitting the bullets to the gun
The 311299 and 314299 bullets are about 200 grains with bore riding noses. The 314299 bullets are a bit larger than 311299s, the noses are larger in diameter, and, until sized, the base bands are larger.
Both bullet molds today are 2 cavity. Mark the cavities so that you can tell which cavity the bullets came from. There is always a difference in bullet weight and some dimensions from one cavity to the other.
Cast bullets are not round, and dimensions of the as cast nose and base bands show this. I cannot ever recall a bullet with dimensions +/- a tenth, (.0001”), and normally 3 or 4 or more tenths difference is the rule.
Bullet fit
The cartridge should chamber with a bit of resistance.
The bullet should not stick in the chamber when the chambered cartridge is extracted. No de-bulleting!
The base of the bullet should be in the neck, not down inside the case. If just the gas check is below the neck, there’s generally no problem.
The nose of the bullet should be engraved by each land of the rifling.
The forward-most end of the front base band should slightly mash into the origin of the rifling.
Increasing the amount of tin and/or antimony in the alloy yield slightly larger bullets.
Sizing the bullet in a lubrisizer makes the nose bump up larger.
Bigger as-cast to sized differences make the nose larger than smaller differences. Size a .314” to .308” and the nose will bump up more than when sizing from .314” to .312”.
Softer bullet noses bump up more than harder bullet noses.
Bullets with base bands sized to different dimensions may/will have different overall lengths.
Rifle barrel lands at the chamber end wear or erode, so that cartridge overall length increases slightly and slowly as the rifle is shot.
If the cartridge that goes in the gun has a lot of base band below the neck, change something.
If the cartridge goes in the gun, has just the gas check in the case mouth and doesn’t engrave the bullet nose, change something.
If both 314299 cavities make bullets too big, go to the 311299. If the 311299 bullets are too small, either the gun or the mold is incorrect.
If both 311299 cavities make bullets that are too small, go to the 314299. If the 314299 bullets are too big, either the gun or the mold is incorrect.
Reloading
Get a set of good cartridge cases from the same lot, at least with the same headstamp.
Full-length size them. (New cases will shorten when fired. Used cases won’t, much.)
Measure the lengths and trim to the same length. (Same length cases are required for proper case mouth “belling” with the “M” die.)
Chamfer the case mouths in and out. (Lee makes inexpensive tools to chamfer case mouths and trim cases to length.)
Bell the case mouths with a Lyman “M” die in a press.
Prime (Lee makes a great and inexpensive priming tool.) Any large rifle primer will work fine.
Cartridge “lot” size is 35, make a set of 35 cartridges for each trial load. (The set of 120 cases allows loading three lots of 35, with thirteen spares.) Just checking.
Charge the cases with powder.
Lyman 48th Edition Reloading Handbook
“308 Win., 311299 at 200 grains
IMR 4227,19.5 grains starting load to 26 grains maximum load”
Start with 18 grains, and then go up in 1-grain steps to 22 grains
“30/06 Springfield, 311299 at 200 grains
IMR 4227, 21 grains starting load to 29 grains maximum load”
Start with 19 grains, and then go up in 1-grain steps to 24 grains
ALWAYS CHECK A PUBLISHED LOAD TO SEE IF IT MAKES SENSE!!!! BELIEVE NO ONE!!!
Inspect the cases with a flashlight to detect “no powder” and “double charges”.
Seat the bullet to the correct overall length.
Shooting
Shoot only on a day with reasonable weather. No hurricanes or blizzards.
Testing a rifle for accuracy requires a solid bench rest on a sold bench, and a good chair or stool. Use a reasonable front and rear rest. Rests can be bought for prices ranging from OK to crazy. I have used a Hoppe’s front rest as well as home made rests, and they all work well.
The target used must work for the shooter-target types, shapes and styles affect group size.
Push a patch through the barrel.
Get comfortable at the bench.
Shoot 3 foulers, and then two 5-shot groups for record in about 15 minutes. Don’t let the barrel get too hot!
Clean the barrel.
Shoot 3 foulers, and then two 5-shot groups for record in about 15 minutes. Don’t let the barrel get too hot!
Clean the barrel.
Shoot 3 foulers, and then ONE 5-shot group for record in about 10 minutes. Don’t let the barrel get too hot!
Clean the barrel.
You’ve shot five 5-shot groups and 9 foulers for 34 shots. What about the #35 cartridge? If you call a honked shot, you’ll need that #35 cartridge to make the fifth shot in the group.
Recording the data
Write everything down. Write the reloading data down when you reload, and the shooting data on the day you shoot. DON’T WAIT FOR TOMORROW, YOU’LL FORGET SOMETHING!
Write down the powder charge and primer make and lot numbers if you wish and the overall length and bullet # and just everything.
If you pull a shot, honk it out of the group; and if you call it honked before you look through the scope; then take another shot for record. Don’t lie to yourself.
AN ASIDE: WHAT TO DO IF THE RIFLE WILL NOT GROUP IN 2” AT 100 YARDS
I write with limited experience, counting on others for help. “Frank 46” and ”The Nyack Kid” on “Cast Boolits”, “linoww” and “runfiverun” on the CBA forum, John Bischoff, William W."Bill" McGraw, Paul Brasky and Dave Goodrich have helped a great deal. Some of their suggestions are in quotes below.
“Shoot the rifle with a good jacketed bullet load. If the gun and load are capable of at least 1.5" groups at 100 yards, the gun should shoot cast bullets accurately.”
“Check for crown damage or a barrel bulge.” Look at the barrel crown under a good light and a magnifying lens, check for any damage. If there is damage, re-crowning the barrel is fairly simple and may cure the problem.
Push a cleaning rod with a tight patch through the barrel, feeling for any sudden lack of resistance that indicates a bulge in the barrel. If there is a barrel bulge, the rifle may not shoot cast bullets accurately. However, I have seen, been told about and read accounts of bulged barrels shooting accurately.
“Have another, experienced, shooter try your rifle. Sometimes your grip/ forearm rest / butt stock rest can cause problems. I had that shown to me once, much to my chagrin, moving the forearm back two inches on the rest cut my groups by 30%”.
For a gun with a “free-floating barrel, check the gun for interference between the barrel and stock. Use something thicker than a dollar bill, maybe 3 dollar bills.
Take the barreled action out of the stock, inspect both for any signs of interference or rubbing or polishing. If there is a sign of interference, sand the stock. This has to do with interference between the action and the stock
Put cardboard shims, matchbook cover ~ .025”, under the front and rear receiver rings, then put the gun together. This will free-float the barrel. If needed, “glass bed” the action in the stock.
Check the scope screws and action screws to make sure that there is nothing loose. I have never used a torque wrench on action screws, yet.
“Check tightness of scope base screws, and scope ring screws.”
”Set action screws with a torque wrench to the approximate tightness you use. The main screw might like 50 inch-pounds and the rear one somewhere around 35 inch-pounds. The third one, if there be one, might be happiest around 20 inch-pounds. Your rifle WILL be different
from all other rifles.”
“Try a different scope.” I have seen and talked to other shooters who have found that the scope sight is defective, and causes inaccuracy. I have never had an inside-adjustable scope that caused inaccuracy, and cured an outside-adjustable Lyman STS scope of this trait by cleaning the adjustment ring.
I have very seldom reached this point without being able to shoot 5-shot 100 yard group averages under 2”. If the steps listed above will not get the rifle shooting under 2”, I don’t know what to do next.
BACK TO THE SEARCH FOR BETTER ACCURACY
If reliably repeatable sets of five-5 shot groups averaging less than 2” at 100 yards have been achieved, and if better accuracy is desired, here are the steps:
I start with a set of at least 120 cartridge cases of the same lot (or at least with the same headstamp). This allows me to load three sets of 35 cartridges, with 15 extras. I put the not-loaded cases in a plastic bag; these are the first cases loaded the next time. This takes care of rotating the cases so that all are loaded about the same number of times.
When a case neck splits, I find it when processing the cases in my hands, (cleaning the neck, de-priming, cleaning the primer pocket, lubricating the case), when sizing, or when belling the case mouth in a press with the Lyman “M” die. Low resistance when pulling the case over the expander button or pushing it over the “M” die can mean a split neck.
When a case neck splits I anneal the necks of all the cases in the lot.
When primer pockets enlarge such that primers are loose, I’ll throw away the set of cases. I shoot lower velocity cast bullets only, and have never had primer pockets enlarge, nor have I ever had a case head separation.
As described above, cases should be trimmed to a common length, case mouths chamfered in and out, and necks belled after sizing.
These steps may increase accuracy, though I have never seen any convincing data or report that shows that. I always do these because they are inexpensive and easy.
Uniform primer pockets
De-burr flash holes
Clean inside case necks with a bronze or (I use) nylon brush. The brush may be chucked in a drill for more speed.
Clean primer pockets
These next steps have worked for me and are roughly in order of their effectiveness in reducing group sizes. Some or all of these steps should get the rifle to shoot 100 yard average sets of five 5-shot groups between 1.5” and 1”. (Based on the CBA National records over several years, competitors average around 1" over the classes. This means that those who shoot in each of the four classes, all told, average about 1". At the 2008 CBA National Tournament 15 shooters shot in Production Class, in the 100 yard, four group, five-shot match. Of the 15, 4 shooters averaged less than 1”, and 11 shooters averaged over 1”. The 15 shooters averaged 1.224” groups. Averaging 1" with cast bullets is tough.)
Change the powder. I have seen substantial changes in group size averages associated with changes in the powder. For example, Paul Brasky recommends A5744 and IMR4198 in 308 Win. CHECK THE RELOADING MANUAL (S)! (Note that these two and other powders don’t go through powder measures accurately. I dribble and weigh charges of these powders.)
Change the powder charge in .5-grain steps. (Powder charges of IMR 4227 were varied above in 1-grain steps.)
Weight segregate bullets. This step is time consuming, but serves to identify the oddball low or high weight bullet that may be a flier.
Adjust the trigger to reduce pull weight and/or over travel and take-up.
Change the bullet hardness
Change sized bullet diameter
Try another bullet
Use wind flags and learn to shoot in the wind.
These steps may reduce group size below 1” 100 yard 5-shot averages. Many are used by good cast bullet shooters. I have never seen any convincing data that any of these steps reduce group size with cast bullets. However, it is equally true that none of these steps will make groups bigger.
Change the lube. There is a wide variety of lubes used by good CB shooters, reinforcing my belief that “reasonable” lube choice has little or no effect on accuracy. This does not mean that one cannot concoct a lube that adversely affects accuracy. I have done so. Hence “reasonable”.
Vary the number of lube grooves filled
Use “better” cases. In modern jacketed bullet bench rest, “better” cases such as Norma or Lapua are said to be more accurate than domestic cases. Some contend that the same is true with cast bullets.
Change the primer.
Change the powder charge in .1-grain steps. For charges above ~ 15 grains of powder, it is my belief that charges in .5 grain steps are as precise as required. Charges of XX.1 or XX.2 produce no accuracy difference from charges of XX.0. Charges of XX.3 or XX.4 produce no accuracy difference from charges of XX.5. Some contend otherwise, data is sadly lacking.
Weigh and control powder charge weights.
Make the cartridge case length = chamber length -.005”. It has been claimed that minimizing the distance in the rifle chamber from the end of the cartridge case to the end of the chamber will increase accuracy. .005” is frequently mentioned as the safe minimum.
Weight segregate the cases.
Weight segregate the primers.
Weight segregate the gas checks.
Anneal the gas checks.
Turn or inside ream the case necks.
Ream the flash holes to a uniform diameter.
Orient the case in the chamber.
Orient the bullet in the chamber.
Orient the bullet in the case and the case in the chamber.
Try different barrel cleaning methods and frequencies.
Check and improve cartridge concentricity.
Vary OAL by .002"? .005”? .010”?
Shoot bullets in the order cast. Recommended by some single shot rifle shooters.
These steps require some substantial money and/or expertise. Between the steps above and these, and with quite a few bucks spent, it may be possible to reliably shoot 100-yard 5-shot groups averaging below 1”.
Size the case necks in a Redding or Wilson replaceable bushing style neck sizer
Seat the bullets with a precision micrometer adjustable sizing die
Glass bed the rifle action.
Ream the chamber throat.
Get a taper die to match the reamed chamber throat and taper the bullets.
Re-crown the barrel.
Lap the barrel.
Replace the barrel.