Typical causes of reduced accuracy and shooting stability

In practice, a decrease in accuracy is rarely caused by a single reason. More often it is a combination of factors: ammunition, component seating, fasteners, firing regime, fouling, wear, and system component compatibility. Below is a list of the most common causes identified during technical diagnostics.

1. Ammunition and its compatibility with the chamber

• Variation in powder charge, differences between powder and primer lots, differences between bullet lots — creates velocity instability and vertical dispersion.
• Non-uniformity of cases in terms of service life and geometry (neck, shoulder, base) — alters lockup conditions and pressure regime.
• Deviations in bullet seating parameters (depth, tension, runout) — affect the repeatability of bullet start and contribute to dispersion.
• Unsuitable velocity regime/pressure for a specific system — may yield acceptable results with a low round count, but leads to degradation of stability as wear and fouling accumulate.

2. Optical sight and mounting components

• Insufficient fixation or incorrect torque on base/ring screws — causes point-of-impact shift and reduced repeatability.
• Misalignment during installation, stress in the scope tube, non-concentricity of seating surfaces — leads to instability during string firing.
• Damage to optics or internal mechanisms from impacts/transport/recoil — manifests as an unstable point of impact and a 'floating' zero.

3. Stock, receiver bedding, and load-bearing structure

• Unstable receiver bedding in the stock, lack of repeatability after disassembly/reassembly — leads to changes in system behavior and point-of-impact shift.
• Barrel contact with the stock during heating, unwanted contact points — causes group shift as temperature and rate of fire change.
• Insufficient rigidity/improper load distribution in the load-bearing structure — causes variability in component behavior during recoil.

4. Bolt group and locking mechanism

• Variable bolt closing force (influenced by fouling, ammunition geometry, wear) — alters firing conditions and degrades repeatability.
• Galling, wear, and unstable contact surface of locking lugs — leads to point-of-impact shift and reduced accuracy.
• Disruptions in extraction/case support function — alter chamber conditions and affect stability.

5. Barrel and chamber

• Barrel bore fouling (copper, carbon) and deviation from the cleaning schedule — directly affects stability and group characteristics.
• Overheating and changes in rate of fire — leads to group shift and increased dispersion due to thermal factors.
• Erosion of the bullet throat and changes in bullet start conditions — requires adjustment of seating and regime, otherwise accuracy degrades.
• Ammunition and chamber compatibility failure — manifests as unstable lockup, increased extraction force, reduced repeatability, and risk of sudden pressure spikes.

6. Muzzle devices and seating surfaces

• Muzzle device misalignment, cant, fouling, unstable seating — leads to asymmetric gas exit and reduced accuracy.
• Differences in torque and installation conditions from session to session — causes point-of-impact shift.

7. Shooting conditions and methodology

• Differences in rest, bags, bipods, cheek weld, and load applied to the rifle — creates variability in results with unchanged mechanics.
• Incomparable firing conditions (cold/hot barrel, different pauses, different strings) — lead to incorrect conclusions about accuracy.
• Errors in trigger control and hold — often masquerade as a 'hardware problem' but manifest in a repeatable pattern.

A decrease in accuracy is, as a rule, not a 'single cause' but a cumulative effect. Therefore, the correct approach begins with technical diagnostics:

• recording the actual condition of the system;
• checking ammunition and chamber compatibility;
• identifying the factors limiting performance;
• developing a prognosis and technical recommendations for improvements.