October 17th, 2015

Online Barrel Weight Calculator from Pac-Nor

Online Pac-Nor Barrel Calculator

Can you guess what your next barrel will weigh? In many competition disciplines, “making weight” is a serious concern when putting together a new match rifle. A Light Varmint short-range Benchrest rifle cannot exceed 10.5 pounds including scope. An F-TR rifle is limited to 18 pounds, 2 oz. (8.25 kg) with bipod.

One of the heaviest items on most rifles is the barrel. If your barrel comes in much heavier than expected, it can boost the overall weight of the gun significantly. Then you may have to resort to cutting the barrel, or worse yet, re-barreling, to make weight for your class. In some cases, you can remove material from the stock to save weight, but if that’s not practical, the barrel will need to go on a diet. (As a last resort, you can try fitting a lighter scope.)

Is there a reliable way to predict, in advance, how much a finished barrel will weigh? The answer is “yes”. PAC-NOR Barreling of Brookings, Oregon has created a handy, web-based Barrel Weight Calculator. Just log on to Pac-Nor’s website and the calculator is free to use. Pac-Nor’s Barrel Weight Calculator is pretty sophisticated, with separate data fields for Shank Diameter, Barrel Length, Bore Diameter — even length and number of flutes. Punch in your numbers, and the Barrel Weight Calculator then automatically generates the weight for 16 different “standard” contours.

Calculator Handles Custom Contours
What about custom contours? Well the Pac-Nor Barrel Weight Calculator can handle those as well. The program allows input of eight different dimensional measurements taken along the barrel’s finished length, from breech to muzzle. You can use this “custom contour” feature when calculating the weight of another manufacturer’s barrel that doesn’t match any of Pac-Nor’s “standard” contours.

Smart Advice — Give Yourself Some Leeway
While Pac-Nor’s Barrel Weight Calculator is very precise (because barrel steel is quite uniform by volume), you will see some small variances in finished weight based on the final chambering process. The length of the threaded section (tenon) will vary from one action type to another. In addition, the size and shape of the chamber can make a difference in barrel weight, even with two barrels of the same nominal caliber. Even the type of crown can make a slight difference in overall weight. This means that the barrel your smith puts on your gun may end up slightly heavier or lighter than the Pac-Nor calculation. That’s not a fault of the program — it’s simply because the program isn’t set up to account for chamber volume or tenon length.

What does this mean? In practical terms — you should give yourself some “wiggle room” in your planned rifle build. Unless you’re able to shave weight from your stock, do NOT spec your gun at one or two ounces under max based on the Pac-Nor calculator output. That said, the Pac-Nor Barrel Weight Calculator is still a very helpful, important tool. When laying out the specs for a rifle in any weight-restricted class, you should always “run the numbers” through a weight calculator such as the one provided by Pac-Nor. This can avoid costly and frustrating problems down the road.

Caution: Same-Name Contours from Different Makers May Not be Exactly the Same
One final thing to remember when using the Barrel Weight Calculator is that not all “standard” contours are exactly the same, as produced by different barrel-makers. A Medium Palma contour from Pac-Nor may be slightly different dimensionally from a Krieger Medium Palma barrel. When using the Pac-Nor Barrel Weight Calculator to “spec out” the weight of a barrel from a different manufacturer, we recommend you get the exact dimensions from your barrel-maker. If these are different that Pac-Nor’s default dimensions, use the “custom contour” calculator fields to enter the true specs for your brand of barrel.

Credit Edlongrange for finding the Pac-Nor Calculator

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