When any rifle which should be a shooter begins to print wider groups, the reason is not in most cases a secret. More frequently it is a pile of little, mechanical inconsistencies, some in the rifle, some in the optic, and some at the points of contact between the shooter and the gun. The trick is to differentiate between the myth of ammunition and the issues that physically shift the system or alter the vibration of the system between the shots.
1. Loose scope rings and bases
There is nothing like an optic that is shifting under recoil to open up the groups. The typical symptom is a rifle which suddenly begins to drop fliers in various directions without an apparent rhythm, and then it jumps full on point of impact after a ring finally slips. Shooters have a tendency to spend a range session in pursuit of load issues only to realize that the fasteners have gone loose. The reason why correct torque and periodical checking is important is because overly loose rings may wobble and too tight may cause some damage to the scope tube and result in issues that resemble broken ammunition. The essence of the problem is in the fact that Browning advises to adhere to the recommended torque settings because stability is the priority.
2. Ring contact in its inappropriate place
A scope may be narrow and yet be incorrect. When rings come into contact with something other than the main tube, e.g. the magnification ring, objective bell or turret saddle, the body of the scope may be bound and will not react to recoil in a predictable manner. Small contact points may produce shot to shot variation that might simulate parallax error or poor fundamentals. It is easy to check in practice, the only thing to be done is to make sure the rings are lying on the straight part of the tube and that the caps or accessories do not bump the rifle.
3. Non-tracking unleveled optics
A canted scope of a little angle may be concealed in an average cluster at short range. It becomes a diagonal miss, and baffling corrections as distance increases as the adjustments in elevation no longer occur in a straight upward and downward movement of the reticle as far as the rifle is concerned. This, says Browning, is much more obvious at greater distances and emphasises the fact that by leveling, the optic and bore are actually levelled, and not eyeballed in loose rings.
4. Unstable bipod load and pelvic pressure
A bipod-fired rifle is not free-floating in reality-all interfaces are springs. On the SnipersHide discussion, one of the shooters noted a low-quality bipod, sliding on a wooden bench, which could not consistently provide forward load; the follow-up stated that butt pressure and cheek weld pressure may alter harmonics. The same thing happens with the rear bags: they can turn a steady rifle into a new rifle each time a different squeeze or shoulder pressure or toe placement happens.
5. Action screw torque which varies the vibration of the rifle
Stocks and actions are clamped systems, and the change of clamp force alters the distribution of stress. The rimfire shooters interpret this radically, although it can be applied more generally: when tightening a screw bends the stock, the motion can sit in a new position and a barrel can acquire new foci of force. The RimfireCentral contributor simply summarized it: it is possible to change effective barrel harmonics with changing tension. Pillar bedding decreases stock-compression variable although it does not remove the necessity of regular torque and regular assembly order following cleaning or transit.
6. Contact between barrel channels and pressure points moving
A come and go group widener is a barrel that is intermittently in touch with the stock. The location of contact can vary with heat, humidity, sling tension, bipod load and even the hand placement. There are rifles which ought to be shot with a deliberate pressure pad close to the fore-end tip; and there are those which call for actual clearance. Contact alone will not kill the accuracy: it is transforming contact with each shot or session.
7. Velocity figures which lose time
Low ES/SD may appear scientific on a chronograph, but brief bands at 100 yards are not consistently consistent with those data. In the AccurateShooter thread, and the SnipersHide discussion, senior shooters have stressed the statement that the standard deviation is not a good predictor of group size at short range; the timing of the barrel and harmonics is the key issue. According to the reply of one AccurateShooter, the Lower ES/SD groups are not necessarily better groups since the time when the bullet exits during the oscillation of the barrel is what counts. Velocity dispersion is manifested as vertical dispersion at longer distance, yet at 100 they are frequently obscured by minute handling irregularities.
8. Swings in the seating depth which relocate a load out of a node
Minor variations in seating depth may relocate a pressure curve and exit time to convert a promising load into a scattered pattern with no additional modifications. One approach that is explained on SnipersHide begins at approximately.020 off the lands and proceeds further and further in larger steps to determine what the barrel prefers, and then tests this with another group at the optimum depth. It is all about discipline: vary a single variable at a time, and verify the outcome rather than relying on one small sample.
9. Fouling control that restarts the behavior of the bore
Certain rifles become tighter, and after a few rounds, causing foulings; some become looser, and the carbon collects in the throat. The same clean-every-trip habit still exists in the older times; but in the more recent anecdotes presented in circles dealing with precision computing there is a very broad discrepancy between cartridge and barrel. One SnipersHide member mentioned 50 to 60 rounds to get to copper equilibrium, the other said that the accuracy would get bad after cleaning and that it would go back to normal when the bore settled. The aspect of over-cleaning also adds inconsistency to itself when the rifle is continually moving through the bare steel and a stabilized fouled state.
Open groups do not occur as a result of one dramatic failure. More frequently they are due to a system that is not changing drastically, that is, the fasteners are loosening, the pressure points are moving, the support inputs are changing, or the bore switches back and forth. The most trusted repair is the low gloss ones: check the optic mount, standardize the torque and assembly, manage the contact points and treat the chronograph figures as an ancillary data and not a guarantee of tight groups.
