Tuesday, April 5, 2011

Analyzing accuracy in a rifle

Note the hidious new camouflage the army "developed" - pathetic and stands out like a sore toe, and to think they could have had the Multicam! (More on camo later)

A post from Total Survivalist Libertarian Rantfest made me think of this bit of info about rifles.

The posts were generally about the new Army Stoner weapons platform in 7.62x51 NATO (.308 win) the "AR-10" XM110 SASS model rifle.

While the Stoner platform is quite old (and outdated IMO) the M14 is even older (based on the M1), the Stoner designed system is easier to produce and "make accurate" with less effort than is needed with the M1/M14 Garand system. and has features that make in inherently more accurate, many that are shared by the common bolt action rifle (that of course can be more accurate than either rifle system.

Of course the largest problem with the direct impingement system is heat (from the ejection gasses) and contamination (gas produced and from outside the action - ie: dirt, sand) induced failure - as our military is intimately familiar with the Stoner design and trained on it's weaknesses this should not be a excessive problem (particularly in this role).

Accuracy in a rifle depends on several things (strictly the mechanical design and construction).

First think about accuracy without the shooter, (outside of mechanical problems the shooter is ALWAYS the point of fail as the most inconsistent part of the total).

What are the most accurate rifles in the world?

The most accurate rifles are not sniper rifles, hunting rifles, or varmint rifles but the Benchrest rifles (Starting cost 3-4k and up, stock, action, barrel - scope extra). Benchrest rifles are designed to eliminate the shooter as much as possible (at least from his physical limitations, grip trigger pull etc.). There are two classes of rifle the Light category at 16.5 to 17 lbs and The heavies are rifles that often have stocks that are CNC produced of solid aluminum or laminated wood and the weight is unlimited, a typical Heavy would be 35 lbs. or heavier. Groups of ten shots within 8 inches at 1000 yards are top scoring! World record is under five inches, a five to six inch group is considered exceptional.

  • Quality Materials
  • Tight repetitive action movement
  • Lack of conflicting or interfering forces
  • Lack of vibration, or repetitive vibration dampening
  • The straightness of parts alignment
  • Consistent and tight locking

Why list all of that - because the Stoner platform is inherently more accurate than the M14. It is more accurate because of design such as the bolt that slides straight back, the locking head of the bolt only turns slightly to lock and the barrel can have all but the gas return tube detached and away from the barrel.

All larger capacity rounds will gain accuracy with a shorter "squat" metallic case for more even burn of powder - the main reason .308 is more accurate and consistent than the 30-06.

That is the mechanical part - true accuracy comes from the ability of the shooter to judge external conditions (grade, wind, distance, humidity, temp., and elevation/air pressure).

The Stoner platform mechanical flaws rest in the tight fitting of the bolt inside the action, the fact that forward movement and contact with the bolt head and the cartridge to be fed into the breech causes the bolt head to turn slightly and cause the lug on the side rear of the head to dig into the side of the action (no spring to resist such as the HK 416) with the addition of even modest fouling or contamination this can cause several types of failure.

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