Accuracy Of The M14/M1A Rifle
I’m not an engineer, but I have come to understand, to a small
degree, the workings of the M14 and how various parts are effected as a
result of the projectile being forced down the barrel under extreme
pressure. About the only way to see how much movement is involved
requires the use of a high speed camera so it can be shown in very slow
motion. The
barrel does whip as the bullet travels down the bore. It exerts
tremendous torque caused by the spin of the rifling. Since the bullet is
usually over sized compared to the diameter of the bore the barrel also
bulges as the bullet passes through. The steel used in the barrel
allows the barrel to return to it’s original size and position after
each shot. It’s not so brittle that it would shatter from the impact or
so soft that it changes it’s set. These factors are important in all barrels. It’s easiest to maintain
accuracy in a barrel that is completely free floating so that no outside
factors effect it’s accuracy.
By WestTexasHunter
By burningsyn
The M14 rifle is a different animal altogether. As with all gas operated rifles, there are several appendages that are directly attached to the barrel. These include the op rod guide, gas cylinder assembly and flash suppressor assembly. To make matters worse, some of these appendages include moving parts like the operating rod and gas piston. So, we have many factors that effect accuracy due to changes in barrel harmonics caused by the parts attached to the barrel.
Improving the accuracy of the M14 is simply a matter of selecting high quality parts and insuring that they function as consistently as possible.
Starting with the barrel, it must be consistent in dimensions though out it’s bore. If any taper is present it should be tighter at the muzzle, not the other way around and taper no more than .0001” (one ten thousandths of an inch). In match grade rifles, heavy barrels are preferable. Medium to heavy weight barrels tend to be stiffer which resists internal pressures and outside influences better than lighter standard barrels.
Parts attached to the barrel must be snug fitting and should not have rotational movement. The barrel may have to be knurled and it’s splineways peened to insure attached parts have no movement. Note that the gas cylinder lock and flash suppressor castle nut should not be over tightened as it can constrict the bore and cause inaccuracy. It is preferable to have the gas cylinder lock hand tight at about the 4:30 to 5:00 o’clock position. If it comes up hand tight at 3:00 o’clock or so, it can place enough pressure on the barrel to bind the gas cylinder causing the piston to stick and/or effect the rifles point of impact. A gas lock that tightens past the 6 o’clock position, but not past 12 o’clock, is acceptable. The gas lock should be backed off to index and the plug tightened to draw the gas cylinder forward.
To improve consistency, the gas system needs to be unitized. Welding or screwing the barrel band to the gas cylinder work equally as well, however I feel the screwed together method is better because it can be easily repaired if necessary, while welds cannot. Properly installed screws, epoxied and staked in place rarely come loose. Unitizing prevents the barrel band from floating and helps instill stabilizing pressure on the barrel in a properly glass bedded rifle.
The operating rod is another area of concern. The op rod should move freely, opening and closing the bolt under it’s own weight when the rifle is tilted 60 degrees up and down. The op rod should also have a minimum of movement (wiggle) in the op rod way of the receiver. It’s also important that the operating rod rest against the piston when fully forward. A gap can result in vertical stringing on the target.
The flash suppressor should be snug on the barrel with no rotational movement in the splineways. Again, be careful not to over tighten the castle nut. Once it’s finger tight, it should be tightened with the pliers about one to one and one half notches only. Flash suppressors on accurized rifles should also be reamed to .406” at the muzzle. Reaming does two things. First it helps prevent rain water from accumulating on the wider bottom web of the suppressor. A drop of water can deflect the bullet resulting in a change to the POI. Second, reaming is an accuracy enhancement. It allows gasses to flow around the bullet with less disturbance. Note that the wider bottom web of the suppressor tends to cause higher pressure against the bottom of the bullet in an unreamed suppressor pushing the bullet upward. A reamed flash suppressor lessons this effect.
All of these methods have been developed over many years of producing match grade M14 rifles by military armorers. They work and are time tested.
I have always used the 6 o’clock hold when sighting on a target during competition shoots. The 6 o’clock hold produces very consistent results for most competitors. Some shooters prefer the center of mass or Navy hold. This can work well in some circumstances. At short range it’s not difficult to judge that the top of the front sight blade is centered on the target. During rapid fire stages, the coach may give the shooter a command to favor right or left and the shooter is supposed to hold about one half of the front sight blade width further out on this command. This is done because there isn’t enough time to adjust the sights for wind changes that effect bullet placement. The problem with using a 6 o’clock hold is that the narrower blade on a NM front sight tend to result in the shooter following the curve of the target black resulting in high shots when given the favor command. The center hold works better in this instance.
Some shooters prefer the standard width front sight over the NM sight because they can execute a favor without the front sight tending to follow the curve while shooting with a 6 o’clock hold. Food for thought…
The vast majority of competition shooters use the 6 o’clock hold. It gives more consistent results under most circumstances and works best at long range.
By Ted BrownBy WestTexasHunter
By burningsyn
The M14 rifle is a different animal altogether. As with all gas operated rifles, there are several appendages that are directly attached to the barrel. These include the op rod guide, gas cylinder assembly and flash suppressor assembly. To make matters worse, some of these appendages include moving parts like the operating rod and gas piston. So, we have many factors that effect accuracy due to changes in barrel harmonics caused by the parts attached to the barrel.
Improving the accuracy of the M14 is simply a matter of selecting high quality parts and insuring that they function as consistently as possible.
Starting with the barrel, it must be consistent in dimensions though out it’s bore. If any taper is present it should be tighter at the muzzle, not the other way around and taper no more than .0001” (one ten thousandths of an inch). In match grade rifles, heavy barrels are preferable. Medium to heavy weight barrels tend to be stiffer which resists internal pressures and outside influences better than lighter standard barrels.
Parts attached to the barrel must be snug fitting and should not have rotational movement. The barrel may have to be knurled and it’s splineways peened to insure attached parts have no movement. Note that the gas cylinder lock and flash suppressor castle nut should not be over tightened as it can constrict the bore and cause inaccuracy. It is preferable to have the gas cylinder lock hand tight at about the 4:30 to 5:00 o’clock position. If it comes up hand tight at 3:00 o’clock or so, it can place enough pressure on the barrel to bind the gas cylinder causing the piston to stick and/or effect the rifles point of impact. A gas lock that tightens past the 6 o’clock position, but not past 12 o’clock, is acceptable. The gas lock should be backed off to index and the plug tightened to draw the gas cylinder forward.
To improve consistency, the gas system needs to be unitized. Welding or screwing the barrel band to the gas cylinder work equally as well, however I feel the screwed together method is better because it can be easily repaired if necessary, while welds cannot. Properly installed screws, epoxied and staked in place rarely come loose. Unitizing prevents the barrel band from floating and helps instill stabilizing pressure on the barrel in a properly glass bedded rifle.
The operating rod is another area of concern. The op rod should move freely, opening and closing the bolt under it’s own weight when the rifle is tilted 60 degrees up and down. The op rod should also have a minimum of movement (wiggle) in the op rod way of the receiver. It’s also important that the operating rod rest against the piston when fully forward. A gap can result in vertical stringing on the target.
The flash suppressor should be snug on the barrel with no rotational movement in the splineways. Again, be careful not to over tighten the castle nut. Once it’s finger tight, it should be tightened with the pliers about one to one and one half notches only. Flash suppressors on accurized rifles should also be reamed to .406” at the muzzle. Reaming does two things. First it helps prevent rain water from accumulating on the wider bottom web of the suppressor. A drop of water can deflect the bullet resulting in a change to the POI. Second, reaming is an accuracy enhancement. It allows gasses to flow around the bullet with less disturbance. Note that the wider bottom web of the suppressor tends to cause higher pressure against the bottom of the bullet in an unreamed suppressor pushing the bullet upward. A reamed flash suppressor lessons this effect.
All of these methods have been developed over many years of producing match grade M14 rifles by military armorers. They work and are time tested.
I have always used the 6 o’clock hold when sighting on a target during competition shoots. The 6 o’clock hold produces very consistent results for most competitors. Some shooters prefer the center of mass or Navy hold. This can work well in some circumstances. At short range it’s not difficult to judge that the top of the front sight blade is centered on the target. During rapid fire stages, the coach may give the shooter a command to favor right or left and the shooter is supposed to hold about one half of the front sight blade width further out on this command. This is done because there isn’t enough time to adjust the sights for wind changes that effect bullet placement. The problem with using a 6 o’clock hold is that the narrower blade on a NM front sight tend to result in the shooter following the curve of the target black resulting in high shots when given the favor command. The center hold works better in this instance.
Some shooters prefer the standard width front sight over the NM sight because they can execute a favor without the front sight tending to follow the curve while shooting with a 6 o’clock hold. Food for thought…
The vast majority of competition shooters use the 6 o’clock hold. It gives more consistent results under most circumstances and works best at long range.
Shooters Den
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