Written by Steve Tucker, this article appeared in the Nov/Dec 1999 #142, issue of the Fouling Shot.
The 9mm Luger has a reputation for mediocre accuracy with jacketed bullets and a worse reputation with cast bullets. Much of this notoriety is due to the many military and police pistols, most intentionally made loose to guarantee functioning when dirty, and many worn from extensive use. Part of the problem is caused by the generous chambering chosen in some guns to insure feeding. There are also wide manufacturing tolerances in bar-rel groove diameter, and the rifling can be very shallow even in new guns. A contributing factor may be the NATO standard twist rate of one turn in 10 inches, when a twist rate half that fast would stabilize any normal 9mm Luger bullet.
None of this reflects on any basic inaccuracy in the cartridge, as well made 9mm pistols are capable of excellent accuracy. Many inaccurate guns have been made into good shooters by installing a Bar-Sto or Briley barrel with a tight fit in the slide, minimum dimension chamber, and deep rifling with slower twist rate. A properly fit 9mm pistol is capable of top notch accuracy with jacketed bullets, but as many shooters have found out, this does not necessarily carry over to cast bullets. There are inherent characteristics of the 9mm that make loa-ing accurate cast bullet ammunition more difficult.
First: The 9mm is a high-pressure cartridge, normal operating pressure is 35,000 psi. The 9mm operates at pressures that require special care when shooting cast bullets. Second: Chambering variations in 9mm pistols can negatively affect cast bullet accuracy far more than they do with jacketed bullets. For the above reasons, successful 9mm cast bullet loads are quite different from jacketed bullet loads and bullet fit is important to suc-cess.
With increasing pressure, fit in the barrel and forcing cone becomes progressively more important with cast bullets. Most cast bullet shooters know that cast bullets need to be larger than the groove diameter for best results. Groove diameters in 9mm barrels vary from 0.354” to 0.361”. This extreme variation means a barrel must be measured. Forcing cone fit means that the bullet seats into the forcing cone or leade when chambered. The effect of seating the bullet to an Over All Length (OAL) to contact the leade can be a 25% to 50% reduction in group size. This represents a huge improvement and is easily detected even in offhand shooting.
For example, in the EAA Witness, the Lyman #356402 seated to an OAL of 1.110” averaged 6.5” 25 yd. groups. Seating the bullet to an OAL of 1.243” resulted in 3” average 25 yd. groups. The long OAL rounds were far more accurate, but were over maximum OAL and would not fit in the magazine. They had to be chambered by hand and exposed the grease groove. This bullet is not suitable for loading in this length leade.
Leade length in a gun is easy to determine by loading a jacketed bullet of an appropriate diameter backwards, and seating it progressively deeper until it will just chamber.
Here is a typical example, this is a new barrel and is not worn, the throat is a taper so the leade length varies with the bullet diameter:
0.355” bullet 0.139”
0.357” bullet 0.120”
0.358” Bullet 0.112”
It is apparent that the projection out of the case needs to be quite long to engage the forcing cone. This throat is more than .360” at the case mouth, and easily accepts .358” bullets. Groove diameter is 0.356”, so 0.357” or 0.358” bullets work well.
A survey of more than thirty 9mm pistols, including both current production guns and older military and commercial models, showed that there is no standard throating in 9mm Luger pistols. Both the length and diameter of the throating varied over a wide range. Diameters at the case mouth ranged from 0.357” to 0.362”, some guns had a short cylindrical section, most were a straight taper. Leade length at 0.357” ranged from 0.050” to more than 0.210”, and the average was more than 0.110”. Some of the longest throats were in new guns.
In order to be suitable for leade seating, a bullet needs an ogive short enough to allow the full diameter body to contact the leade. It also needs a front band wide enough so that the grease groove is not exposed. With bullets lighter than 100 grains it is not possible to have both an ogive and the necessary band length. Bullets of 115 grains can be designed to leade-seat in short leade barrels, but loads powerful enough to work the action may develop pressure too high for best accuracy. I have found that maximum utility in 9mm Luger cast bullets is in the weight range of 120 to 140 grains. Bullets heavier than 140 grains need a tapered or gas check base to pre-vent interference with the case wall taper.
There is one more requirement for a good leade seating cast bullet design, that is a definite step or angle between the ogive and the front band. When rounds are seated into the leade, variations in bullet body length cannot be tolerated. When the bullet has a tangent ogive, variations in cast diameter cause large variations in body length after sizing. A long body bullet will cause a jam, because cartridge headspace is too long to fit the chamber. Cast bullet designs need a defined end to the top of the front band. This can be a small step, a secant ogive, or a shallow angle. Choice of the correct bullet design is a critical first step in loading cast bullets in the 9mm. Unfortunately many of bullet molds offered for 9mm closely copy the jacketed bullet profile, a long ogive with a very short bullet body.
The photograph shows some typical 9mm bullets in order of their leade seating length. The leade lengths given assume the grease groove is 0.010” below the case mouth. The very common Lyman designs 356242 and 356402 are suitable only for short leades. You need a leade seating length over 0.110” in order to leade-seat in the average 9mm Luger pistol.
The 9mm Luger has a reputation for mediocre accuracy with jacketed bullets and a worse reputation with cast bullets. Much of this notoriety is due to the many military and police pistols, most intentionally made loose to guarantee functioning when dirty, and many worn from extensive use. Part of the problem is caused by the generous chambering chosen in some guns to insure feeding. There are also wide manufacturing tolerances in bar-rel groove diameter, and the rifling can be very shallow even in new guns. A contributing factor may be the NATO standard twist rate of one turn in 10 inches, when a twist rate half that fast would stabilize any normal 9mm Luger bullet.
None of this reflects on any basic inaccuracy in the cartridge, as well made 9mm pistols are capable of excellent accuracy. Many inaccurate guns have been made into good shooters by installing a Bar-Sto or Briley barrel with a tight fit in the slide, minimum dimension chamber, and deep rifling with slower twist rate. A properly fit 9mm pistol is capable of top notch accuracy with jacketed bullets, but as many shooters have found out, this does not necessarily carry over to cast bullets. There are inherent characteristics of the 9mm that make loa-ing accurate cast bullet ammunition more difficult.
First: The 9mm is a high-pressure cartridge, normal operating pressure is 35,000 psi. The 9mm operates at pressures that require special care when shooting cast bullets. Second: Chambering variations in 9mm pistols can negatively affect cast bullet accuracy far more than they do with jacketed bullets. For the above reasons, successful 9mm cast bullet loads are quite different from jacketed bullet loads and bullet fit is important to suc-cess.
With increasing pressure, fit in the barrel and forcing cone becomes progressively more important with cast bullets. Most cast bullet shooters know that cast bullets need to be larger than the groove diameter for best results. Groove diameters in 9mm barrels vary from 0.354” to 0.361”. This extreme variation means a barrel must be measured. Forcing cone fit means that the bullet seats into the forcing cone or leade when chambered. The effect of seating the bullet to an Over All Length (OAL) to contact the leade can be a 25% to 50% reduction in group size. This represents a huge improvement and is easily detected even in offhand shooting.
For example, in the EAA Witness, the Lyman #356402 seated to an OAL of 1.110” averaged 6.5” 25 yd. groups. Seating the bullet to an OAL of 1.243” resulted in 3” average 25 yd. groups. The long OAL rounds were far more accurate, but were over maximum OAL and would not fit in the magazine. They had to be chambered by hand and exposed the grease groove. This bullet is not suitable for loading in this length leade.
Leade length in a gun is easy to determine by loading a jacketed bullet of an appropriate diameter backwards, and seating it progressively deeper until it will just chamber.
Here is a typical example, this is a new barrel and is not worn, the throat is a taper so the leade length varies with the bullet diameter:
0.355” bullet 0.139”
0.357” bullet 0.120”
0.358” Bullet 0.112”
It is apparent that the projection out of the case needs to be quite long to engage the forcing cone. This throat is more than .360” at the case mouth, and easily accepts .358” bullets. Groove diameter is 0.356”, so 0.357” or 0.358” bullets work well.
A survey of more than thirty 9mm pistols, including both current production guns and older military and commercial models, showed that there is no standard throating in 9mm Luger pistols. Both the length and diameter of the throating varied over a wide range. Diameters at the case mouth ranged from 0.357” to 0.362”, some guns had a short cylindrical section, most were a straight taper. Leade length at 0.357” ranged from 0.050” to more than 0.210”, and the average was more than 0.110”. Some of the longest throats were in new guns.
In order to be suitable for leade seating, a bullet needs an ogive short enough to allow the full diameter body to contact the leade. It also needs a front band wide enough so that the grease groove is not exposed. With bullets lighter than 100 grains it is not possible to have both an ogive and the necessary band length. Bullets of 115 grains can be designed to leade-seat in short leade barrels, but loads powerful enough to work the action may develop pressure too high for best accuracy. I have found that maximum utility in 9mm Luger cast bullets is in the weight range of 120 to 140 grains. Bullets heavier than 140 grains need a tapered or gas check base to pre-vent interference with the case wall taper.
There is one more requirement for a good leade seating cast bullet design, that is a definite step or angle between the ogive and the front band. When rounds are seated into the leade, variations in bullet body length cannot be tolerated. When the bullet has a tangent ogive, variations in cast diameter cause large variations in body length after sizing. A long body bullet will cause a jam, because cartridge headspace is too long to fit the chamber. Cast bullet designs need a defined end to the top of the front band. This can be a small step, a secant ogive, or a shallow angle. Choice of the correct bullet design is a critical first step in loading cast bullets in the 9mm. Unfortunately many of bullet molds offered for 9mm closely copy the jacketed bullet profile, a long ogive with a very short bullet body.
The photograph shows some typical 9mm bullets in order of their leade seating length. The leade lengths given assume the grease groove is 0.010” below the case mouth. The very common Lyman designs 356242 and 356402 are suitable only for short leades. You need a leade seating length over 0.110” in order to leade-seat in the average 9mm Luger pistol.
9mm cast bullets, with maximum leade seat lengths:
Left to right: Lyman 356242, 0.046”; Lyman 356402, 0.062”; Oregon Trail 135 RNBB, 0.082”; Hensley and Gibbs 275, 0.087”; Saeco 377, 0.091”; Hensley and Gibbs 318, 0.113”; Oregon Trail 124 RNBB, 0.115”; Lee 356-125-2R, 0.116”; NEI 133, 0.166; NEI 116C, 0.178”
Left to right: Lyman 356242, 0.046”; Lyman 356402, 0.062”; Oregon Trail 135 RNBB, 0.082”; Hensley and Gibbs 275, 0.087”; Saeco 377, 0.091”; Hensley and Gibbs 318, 0.113”; Oregon Trail 124 RNBB, 0.115”; Lee 356-125-2R, 0.116”; NEI 133, 0.166; NEI 116C, 0.178”
NEI #133, which is available in 125 grain bevel base and 147 grain gas check versions, can leade-seat in most guns. However this bullet has a truncated cone ogive that can cause feeding problems in pistols designed to function with ball ammo. In order to have a more generally useful bullet I designed NEI #116C. This bullet has an adequate ogive for good feeding and an ogive-body angle that matches the average leade angle in the throat. I designed it with the maximum leade seating length possible with an ogive NEI 116C design dimensions that will feed well.
.Walt Melander at NEI did an excellent job of translating my design into a cherry. The 4 cavity aluminum blocks are perfectly matched and easily cast faultless bullets. The bullet has lived up to my design intentions, giving good feeding and excellent accuracy. NEI #116C is not a “Miracle Bullet,” you still need careful load development to get good accuracy.
NEI 116C design dimensions
The load giving best accuracy is often just powerful enough to function the action, and is seldom over 80% of the maximum load. It is always best to start out as low as possible and work up. The starting loads in some manuals are excessively high for cast bullets, and shooters working up from them may never find the most accurate load. Powders matter, and switching to a slower powder may allow 100 fps more velocity with equivalent accuracy. Powders I have found useful include Bullseye, HP-38 and 231 on the fast end, AA-5, 4756, and Power Pistol on the slow side. Notice that these are all small flake or spherical powders that measure well.
Powder measurement is critical in the 9mm, small charge variations produce large pressure variations.
Pressure variations that go unnoticed with jacketed bullets can destroy cast bullet accuracy. Powder measures that work well with larger rifle charges are sometimes not capable of throwing consistent charges in the 3 to 5 grain range required for 9mm loads. If your powder measure is not capable of throwing small charges with a variation of plus or minus 0.1 grains you should weigh charges or purchase a measure suited to pistol use.
Powder measurement is critical in the 9mm, small charge variations produce large pressure variations.
Pressure variations that go unnoticed with jacketed bullets can destroy cast bullet accuracy. Powder measures that work well with larger rifle charges are sometimes not capable of throwing consistent charges in the 3 to 5 grain range required for 9mm loads. If your powder measure is not capable of throwing small charges with a variation of plus or minus 0.1 grains you should weigh charges or purchase a measure suited to pistol use.
NEI 116C engraves over half its length, giving increased velocity and accuracy potential.
Bullet alloy needs to be sufficiently hard. This is something that varies from gun to gun and load to load. BHN 16 is a good starting point, but some gun/load combinations will require BHN 22 (Linotype) or harder. The bullet hardness giving the best groups may be higher than calculat-ed from the pressure, it pays to experiment. Some commercially cast bullets I have tested were BHN 10, these and commercial swaged lead 9mm bullets are far too soft for any but very light loads.
Case variation in 9mm Luger is extreme and this is especially damaging to cast bullets. Mixed cases can double group size:
-Browning High-Power Federal cases 3.5” average group
-Browning High-Power mixed cases 6.1” average group
Military 9mm cases are frequently thick and have a rapid internal taper, the smaller case volume causes higher pressure. If the base of a cast bullet extends below the taper it can be sized smaller, and this is very destructive to accuracy. Cannelured cases can damage cast bullets, if the base of a cast bullet extends below the cannelure it may create a bulge that prevents chambering.
For loading cast bullets where larger bullet diameters and deep seating may be required, non-cannelured commercial cases are the most satisfactory. In 9mm Luger, single headstamp selection is best for top accuracy and consistent results when testing cast bullets. After load development, you may find that mixed commercial cases can be used satisfactorily for informal shooting. If your gun has a groove diameter of 0.357” or larger and a tight chamber, you may have to select cases with thin walls, or resort to case neck reaming. Case neck reaming is labor intensive, but can provide a way to shoot guns with large groove diameters.
-Browning High-Power Federal cases 3.5” average group
-Browning High-Power mixed cases 6.1” average group
Military 9mm cases are frequently thick and have a rapid internal taper, the smaller case volume causes higher pressure. If the base of a cast bullet extends below the taper it can be sized smaller, and this is very destructive to accuracy. Cannelured cases can damage cast bullets, if the base of a cast bullet extends below the cannelure it may create a bulge that prevents chambering.
For loading cast bullets where larger bullet diameters and deep seating may be required, non-cannelured commercial cases are the most satisfactory. In 9mm Luger, single headstamp selection is best for top accuracy and consistent results when testing cast bullets. After load development, you may find that mixed commercial cases can be used satisfactorily for informal shooting. If your gun has a groove diameter of 0.357” or larger and a tight chamber, you may have to select cases with thin walls, or resort to case neck reaming. Case neck reaming is labor intensive, but can provide a way to shoot guns with large groove diameters.
Left- 4 cavity NEI 116C mold
If your gun is one of the 10% or so with a leade over 0.178” long, there is no cast bullet design available that will leade-seat. If this is the case, you will have to live with the effects of bullet jump. In my tests with 3 guns and several bullets, the effect on accuracy was directly related to pressure. In 1150 fps loads, 0.010” bullet jump gave noticeably larger groups. In 1000 fps loads, accuracy did not noticeably degrade until bullet jump reached 0.020”. When bullet jump exceeded 0.050”, only low pressure loads, under 900 fps were accurate.
The only requirement for accurate low pressure loads is that the bullet be at least 0.001” over the maximum groove diameter. Fast powders like Bullseye work best, and 2.0 to 2.7 grains usually groups well. Depending on bullet weight, velocity will be 750 to 850 fps. Loads this light may not function the action of stock semi-autos. This can be overcome by installing a lighter recoil spring. Light loads can be exceptionally accurate in any gun, and are ideal for plinking at short range, or basement shooting. Just be sure to reinstall the standard recoil spring before firing normal power ammunition.
One thing has become apparent in my testing, and that is each 9mm pistol is different with cast bullet loads. Unlike the 45 ACP, where good cast bullet loads are easy to develop, the 9mm is finicky. As velocity and pressure increase, requirements become more and more exacting, and loads may have to be tailored to each individual pis-tol for best results. Experimenting with powders, sizing diameters and bullet alloys is time consuming. This can be frustrating if the bullet design chosen is not capable of maximizing the accuracy potential of the gun.
There are few good cast bullet designs suitable for leade-seating in the average 9mm Luger throat. Mold makers continue to try to imitate the design of jacketed bullets, and uninformed customers continue to purchase these designs with predictably poor results. Some cast bullet loading data contributes to the problem by recommending loads that are to heavy and by specifying an OAL that guarantees poor results even with well-designed bullets. This is unfortunate, because the 9mm, and other high pressure semi-auto pistol cartridges like it, can shoot cast bullets accurately and provide low-cost shooting enjoyment.
The only requirement for accurate low pressure loads is that the bullet be at least 0.001” over the maximum groove diameter. Fast powders like Bullseye work best, and 2.0 to 2.7 grains usually groups well. Depending on bullet weight, velocity will be 750 to 850 fps. Loads this light may not function the action of stock semi-autos. This can be overcome by installing a lighter recoil spring. Light loads can be exceptionally accurate in any gun, and are ideal for plinking at short range, or basement shooting. Just be sure to reinstall the standard recoil spring before firing normal power ammunition.
One thing has become apparent in my testing, and that is each 9mm pistol is different with cast bullet loads. Unlike the 45 ACP, where good cast bullet loads are easy to develop, the 9mm is finicky. As velocity and pressure increase, requirements become more and more exacting, and loads may have to be tailored to each individual pis-tol for best results. Experimenting with powders, sizing diameters and bullet alloys is time consuming. This can be frustrating if the bullet design chosen is not capable of maximizing the accuracy potential of the gun.
There are few good cast bullet designs suitable for leade-seating in the average 9mm Luger throat. Mold makers continue to try to imitate the design of jacketed bullets, and uninformed customers continue to purchase these designs with predictably poor results. Some cast bullet loading data contributes to the problem by recommending loads that are to heavy and by specifying an OAL that guarantees poor results even with well-designed bullets. This is unfortunate, because the 9mm, and other high pressure semi-auto pistol cartridges like it, can shoot cast bullets accurately and provide low-cost shooting enjoyment.