Belangrikheid van korrekte geweer- en koeël-spesifikasies

  • Wednesday, 29 April 2015 07:50
  • Published in Reloading
  • Read 5008 times

Courtesy of: TechFund Distributors
Hoe belangrik is dit om geweer- en koeël-spesifikasies korrek te verstaan?

Noudat die jagseisoen al aan die gang is en ons almal vroeër of later by die skoonmaak van ons geliefde jaggewere gaan uitkom, is dit raadsaam om weer 'n slag hierna te kyk en deeglik te verstaan dat dit werklik baie belangrik vir die skoonmaak van ons gewere is.

 "Whatever you do, never use any kind of abrasive polish, paste or similar compounds to polish the bore of the barrel. Rifle barrels are manufactured to exacting tolerances and the allowed deviation from specified dimensions vary from 20 to 30 micron. A human hair is 64 micron in diameter. It is easy to polish a barrel beyond allowed dimensions and wind up with a very smooth, oversized bore that will only shoot well with jacketed lead core bullets with thin jackets and the softest of lead cores. Stay away from wire brushes, use a wool mop, rag and jag and chemical cleaners that are ammonia free. If you have a bore snake, give it to someone you don't like.

Here is how it works:

  1. Polishing pastes and abrasive bullets remove metal as they travel down the bore from chamber to muzzle. If they did not remove metal, no polishing would occur.
  2. Any abrasive cuts and removes more metal when it is first used and sharp.
  3. Copper/jacket material fouling is heavier at the muzzle end than at the chamber end of a barrel.
    1. An advert for one of these abrasive products states that it will remove no more than 0.0003" of metal from the bore. It is not clear if it is meant that the barrel will not be enlarged in diameter by more than 0.0003", or whether this is removed from the surface, leaving the bore 0.0006" larger in diameter. 0.0003" is 7.5 micron. It is not clear how much metal is removed by paste cleaners/polishes.
    2. When an abrasive polishing paste is used, it is applied from the chamber end of the barrel. Initially it is sharp and cuts well. As it is pushed down the bore, it becomes more blunt and cuts less. When the applicator is unscrewed from the rod and refitted for the next pass, the process repeats. Slightly more blunt initially, becoming even more blunt as it travels down the bore. This imparts a slight taper to the bore, larger at the chamber end than at the muzzle because more metal is removed from the chamber end than the muzzle end.
    3. When cleaning metal fouling from a barrel, one would look into the muzzle to see if any copper remains. It is usually clearly visible as a yellowish/red deposit on the barrel steel. Let us be optimistic and assume that it is less than 2 micron thick. Polish is applied from the chamber end until the 1 to 2 micron layer of copper is removed. Because there is no copper deposit in the chamber neck area, freebore, leade and the first couple of centimeters of barrel, more than 1 to 2 micron of barrel metal is removed in those areas. (Remember #2 - sharper at the chamber end than at the muzzle end) One cleaning session, to remove all the copper from the muzzle end, will enlarge the chamber neck diameter, freebore and first couple of centimeter of barrel by 2 to 4 micron. It will therefore take somewhere between 5 and 10 cleaning sessions to bring those dimensions to the upper limit of the allowed specification with calibers of .264". With larger calibers, where the tolerance is 30 micron, 7 to 15 sessions will get you there. This is my opinion, based on the observation of cleaning methods and measurement of internal dimensions of more than 200 rifles. On the subject of bore snakes: I have measured marked ovality of the bore at the muzzle on 7 rifles that were inspected for causes of inaccuracy. Every owner also owned a bore snake." ~ Gerard Schultz GS Custom Bullets CC.

Só, once you understand correctly the importance of rifle specifications, why not do your rifle cleaning in the correct way?

'n Koeëlvervaardiger wat bogenoemde gerade ag, kan u aanvaar sal ook sy koeëls binne baie streng toleransie grense vervaardig, bloot omdat hy die belangrikheid daarvan, in verhouding tot u geweer se spesifikasies, korrek verstaan en interpreteer.

Die volgende toleransie grense is van toepassing op GS Custom se dryfband konsep koeëls:

"GSC bullets are designed to the following standard:
Diameter tolerance: + or - 0.005mm (0.0002").
Length tolerance: + or - 0.10mm (0.004").
Weight is within 0.25% of the stated weight.
Uniformity of ogive curve: - + or - 0.005mm (0.0002")."

Wat spel hierdie twee aspekte - geweer- en koeël-spesifikasies - dan uiteindelik vir u as jagter uit? AKKURAATHEID wat u in staat stel om u skootplasing so goed moontlik te kan doen. Dít, plus 'n lang en akkurate skiet lewe van u goed en korrek versorgde jaggeweer.

Al wat u moet doen is om u geweer reg skoon te maak en dan natuurlik die korrekte jagkoeëls telkemale te gebruik.


  • Last modified on Wednesday, 29 April 2015 08:00
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