National Match rifles utilize hooded apertures to reduce glare from the sight picture. Sure there is a large aperture on the “leaf” of an AR15 A2 rear sight, but it is just too big to produce the level of accuracy National Match shooters desire. Fortunately, match leafs are threaded to accept screw-in hoods to, not only reduce glare – but to step the aperture size down to something more reasonable for National Match standards.
Typically, the options available for sizes regarding the actual hole (or peep) that shooters will look through are: .030 / .038 / 0.40 / .042 / .046 / .052
Which is the correct choice? Well… It depends.
When just starting out, ANY of these choices is going to be better than ANY standard non-hooded GI aperture. The reduction in size and the hood alone will be (literally) light and day.
Once a shooter has been at it for a minute, and is maybe questioning a purchase – standard doctrine is to use the smallest option that provides enough light for a clear sight picture, while guaranteeing the ability to sharply focus on the front sight.
Some new shooters will immediately jump to the smallest aperture available (.030). Some aftermarket manufacturers will make even smaller apertures to supply the newer-shooter-demand for such product. But… while a small aperture like this will definitely lend to easier sight alignment, it behooves the shooter to be aware that sacrificing light for sight alignment is the trade-off. Light is needed to get a clear sharp focus on the tip of the Front Sight Post. This is a must!
As skills mature and scores progress, a good shooter will do well to investigate further:
What is more important?
• Being comfortable with the sight picture?
• or smaller and more on-call groups on target?
The only way to truly tell what is correct for an individual shooter is to try them all!
And it only takes 45-rounds of good competition ammo:
Here a shooter takes 9-targets, positioned on the 100-yard short line – and fires 5-round groups into each, stepping through aperture sizes on each target. Only good shooting with solid and calm Natural Point of AIM (NPA) will produce the results desired. It is important to step through one at a time and not just shoot 3X5-round groups with one aperture size before swapping out.
Results on target should reveal which aperture produced the smallest group. Location of the group is not as important here, as sights can always be adjusted. The aperture that produced the smallest group can now be confidently considered the go-to for the rest of the season, barring extreme difference in light conditions from match-to-match.
ADDITIONAL TECHICAL NOTES:
• Leafs from different manufacturers often accept different hoods. Where the actual aperture (peep hole) size is concerned, all common sizes will surely be obtainable. The manufacturing differences regards the thread pitch used to screw in said hood. Typically, these will either be 1/4-32 or 1/4-28 (e.g., White Oak Armament hoods are 1/4-32, where Rock River hoods are 1/4-28).
• Sometimes these hoods are quite long. Long enough to really do some damage to nice shooting glasses. A couple of options:
• WOA hoods are much shorter (shallow) to prevent this occurrence.
• Be sure to mark your sights to ensure a snug fit (more on that here: Rifle & Sight Marking)
It is nice to have different sized apertures in the cart or range-bag should match day commence with unusually bright or dark conditions (think: extremely bright morning glare at Camp Perry all the way to shooting the 600-yard slow-fire portion of the team match during the Creedmoor Cup at Ben Avery when the sun has set entirely).
No matter how well machined these apertures are, even from the best manufacturers – the holes are almost never perfectly on center. On a rare occasion, they’ll come to match – but chances are that will not be the case. Dope will change when swapping out apertures. The change might not be drastic, but it’s good practice to have confident dope (developed on the short line) for different apertures.