September 23, 2010
Today's trend is toward ever-bigger scopes. Maybe it shouldn't be.
The Remington, slim and taut as rifles used to be, wore a scope that was dropped from catalogs long ago. At the time, they seemed right for each other, joined not so much by vintage as by economy of line.
It was a 121 Fieldmaster, a .22 slide-action with an uncanny balance that brought squirrels and crows in front of the muzzle with speed and certainty. Clamped in a sheet-steel mount was a Weaver J4 with a 3/4-inch tube.
Since then, scopes have added girth. Me too. A little, in each case, has proven useful. But like people, scopes too big around the middle neither look good nor perform well.
Back when I was peering through that J4, you could also buy scopes with 7/8-inch tubes (notably the Lyman Alaskan) and with 26mm chassis (Lyman's Challenger and the Stith Bear Cub, plus European models). The one-inch scope, however, gained enough of a following to emerge as the new standard in the U.S.
By the time 30mm scopes appeared Stateside a couple of decades ago, they were upstaging 26mm models in Europe. Big has gotten bigger. Schmidt and Bender now offers 34mm scopes in its tactical line. And just as today's shooters are buying into higher magnification, they seem enamored with oversize tubes.
"A 30mm tube is stronger than a one-inch," an engineer at one optics firm told me. Then, perhaps to add something useful to the obvious, he leaned over, "That's all the benefit you'll see in a hunting scope, unless the erector assembly is also oversize."
He explained--after closing his office door--that many 30mm tubes feature the erector lenses used in comparable one-inch scopes, so there's really no optical advantage.
"You do get increased latitude in the windage and elevation adjustments, because the erector assembly has more room to move." That's jolly good news if you must dial up lots of elevation for very long shooting or correct laterally for a skewed mount. Otherwise, you might as well stay with the one-inch tube.
"Strength is an academic issue," he concluded. "Unless a horse rolls on it, or you drop your rifle off a cliff or drive over it, you'll never test the durability of a one-inch alloy scope body."
Many shooters believe that 30mm scopes are brighter than comparable one-inchers. They're not. Brightness is determined by exit pupil, a function of the front lens diameter and magnification--and, of course, by the quality of and coatings on the lenses.
A 4.5-14x40 scope set at 8X has a 5mm exit pupil, whether the tube is 30mm or an inch in diameter. Now, bigger glass improves resolution, so theoretically the one-inch erectors will play second fiddle to those built specifically for 30mm tubes. But given equal-quality lenses throughout the scope, any difference will be near impossible to see. I've tried to see it and can't.
My preference for one-inch tubes has some basis in tradition. I've grown up with them and think that diameter just looks right--like 16-inch rims on pickup trucks and 11/32 arrow shafts.
Beyond habit, I think the one-inch scope has much to recommend it. A one-inch scope of reasonable front-end dimensions doesn't appear to burden a featherweight rifle. Given longer barrels and beefier stock profiles, the one-inch tube again works because such rifles are typically designed for longer shooting, which dictates big front lenses to match high magnification. So the outfit looks balanced.
A bulky scope on a lightweight rifle looks awkward--like a tall pack on a short mule. It can also impair your marksmanship. Most 30mm tubes carry a big bell that necessitates high mounts and, with them, adds weight. A rifle saddled with a big, heavy scope carries its center of gravity high, and can feel "tippy."
Makers of fine shotguns work hard to put the center of gravity low, between your hands. Fast, accurate shooting results. Top-heavy scopes put weight where it's least conducive to good shooting.
More weight in the barrel can improve accuracy and help you steady the rifle. In contrast, weight high over the receiver does nothing but apply torque to the rifle; in wind it can also act as a sail.
While on ponderous rifles configured for varminting or sniping, the liabilities presented by large scopes are of little or no account, they do matter on rifles you carry up the mountain for deer and elk.
Given the predilection of shooters for bigger objectives, you might excuse bigger tubes as a more fitting platform for the oversize bells. Fair enough. I've yet to see the need for a 50mm front end on hunting scopes, but both they and the 30mm tube are becoming more popular.
The 30mm tube may well become a standard for another generation of shooters, just as the one-inch scope replaced the Alaskan and the Noske and other slim models of the World War II era. Some of us will leave heel marks in the dust along the way.