18 vs 22mm front globe

rmarsh · Post by **rmarsh** » Fri Aug 02, 2013 8:33 am

What are the advantages / disadvantages of each size? International air and 3P smallbore. I have tried both on my daughters rifles. She does not seem to care one way or the other. I have not been able to document any difference in her score or hold on SCATT. Is there really a purpose for both sizes or is it mainly just what a shooter gets used to or personal preference?

bluetentacle · Post by **bluetentacle** » Fri Aug 02, 2013 3:18 pm

The advantage of a bigger globe is that if you are using a lens in the front sight, the bigger lens can be more precisely made--and therefore optically superior--than a smaller one. This is helpful to High Power/Fullbore shooters, who often use lenses to magnify their relatively minuscule targets, and to better see number boards up to 1,000 yards away--important because it's much easier to crossfire in HP due to the closeness of the targets.

That's why HP shooters migrated to 22mm years ago, and now are moving en masse to the monstrous 30mm globes.

For international smallbore, where front lenses are forbidden, there is no advantage to a bigger globe. That's why 18mm is still standard.

Some justifications for bigger front sights are little more than urban legends. Don't let anyone tell you that a bigger glob lets in more light--that's the job of the rear iris!

I do wonder though, why FWB chose to standardize on 22mm globes. Does anyone know?

Dave IRL · Post by **Dave IRL** » Fri Aug 02, 2013 6:12 pm

Also, 22mm foresights are about similar when using a tube to using an 18mm foresight on the standard barrel. I figured that was their real purpose. Would kinda account for FWB using them, since they look to have a longer sight radius as standard with that tube on.

dontshootcritters · Post by **dontshootcritters** » Sat Aug 03, 2013 11:36 pm

Nothing scientific to add apart from I really liked it a lot more having a bigger foresight so 22mm gets my vote every day.

JSBmatch · Post by **JSBmatch** » Sat Aug 10, 2013 11:23 am

I heard that for outdoor shooting such as 50m a wind flag on your firing/target line can be seen easier in the bigger 22-mm globe. FWB just standardized the 22-mm globe for all their rifles, air and small bore. I don't shoot out door prone, so cannot comment whether this works or not.
I guess there will be fans of both sizes.
I switched to a Centra 18-mm on my FWB 700 and prefer it for 10-m indoors.

mobarron · Post by **mobarron** » Mon Aug 12, 2013 12:12 pm

One possible distinguishing factor is how your daughters align the sights. Obviously the 22mm globe is larger and in aligning the front sight in her rear aperture your daughter will probably see a narrower ring of white around the front sight. If that helps or hurts depends on her. My experience outdoors is that the wind flags are not in line with the target and so are generally not visible with either the 18mm or 22mm. Another factor (I just thought of) you can use the regular metal apertures with the 18mm. These have not been available for the 22mm.

rmarsh · Post by **rmarsh** » Mon Aug 12, 2013 9:29 pm

Thanks for all the responses everyone. As I suspected, there does not seem to be a real strong opinion one way or the other. Personally I like the 22mm, but I am not the shooter my daughter is. Those who mentioned possible advantages seemed to lean toward the 22. I just got home from taking my daughter and another kid to the West Virginia University smallbore camp. I asked coach Hammond what he thought and he prefers the 22mm for both air and smallbore. One thing he mentioned that no else mentioned here was that especially younger shooters tend to think they need a smaller front aperture than they really do. When you have a 18mm front globe and a 4.0 or 4.2 aperture, the aperture "looks" larger because it takes up more of the globe, so that can influence the shooter to go to a smaller aperture. He prefers a large aperture and believes it works better with the larger diameter 22mm globe. Thanks again for all the input.....