I am building a crude mock-up of a DShK 12.7 mm (.50 cal) machine gun. I can find information on the length of the barrel, etc but I am wondering if anyone can tell me what diameter of dowel I’d want to use for the barrel.
It doesn’t have to be ridiculously accurate, but I’d like to make it at least semi-accurate.
Wiki link to the weapon: http://en.wikipedia.org/wiki/DSHK
It probably won’t help to say that the inside diameter of the barrel is 0.50 inches, right?
(But knowing that, based on the pictures at wiki that show the barrel end, you can guesstimate the outside diameter. My guess is around 1 - 1.5 inches at the narrowest, though the outside looks like it tapers a bit, depending on the exact model)
Thanks for your reply, Quercus.
I’m thinking about 1" diameter should be close enough for my purposes. I guess I was just wondering if there was something I wasn’t taking into consideration.
And yes, I did realize that the ID would be .5", although not until after I posted the question. D’oh!
Just out of curiosity, how do you plan to bore the whole? Or are you just going to bore the first 12" or so?
This link tells me that a custom made .50 rifle has a barrel diameter of 1.25". That’s a single-shot rifle. I’m thinking that a machine gun designed for with sustained fire would be thicker, due to the heat generated.
I doubt this help much, but DShK barrel itself weight is 12.6 kg. No info about outer diameter, though.
Steel weighs 440 pounds per cubic foot. If we knew how long the barrel was, we could calculate the diameter based on the volume of the annulus (it’s not technically an annulus, but if you drew it on paper, it would be).
Wiki says the barrel length is 1070 mm.
I a have dishka laying around. What is it exactly you need measured? Funny, you have a ruler and no gun. I have the gun and no ruler.
If I can’t find something to measure with, I’ll try to find a quarter or something and take pictures so you can compare. It sounds like you want the outter diameter? I don’t know anything about dowels, so let me know. I dont even know what that is.
Please excuse my rudimentary notation, I’m on my laptop and it’s a pain in the ass to code.
l = 1070 mm = 107 cm
m = 12.6 kg = 12600 g
d = .5 in = 1.27 cm
r = .25in = .635 cm
rho = 7.86 g/cm^3
R = ?
A = pi * (R^2 - r^2)
V = A * l
V = m / rho
A * l = m / rho
A = m / (rho * l)
R^2 - r^2 = m / (rho * l * pi)
R^2 = (m / (rho * l * pi)) + r^2
R = sqrt((m / (rho * l * pi)) + r^2)
R = sqrt((12600 / (7.86 * 107 * 3.142)) + .635^2)
R = 2.27 cm = .89"
D = 4.54 cm = 1.78" = 1 3/4"
So, an inch and three quarters dowel ought to suit your purposes just fine.
*crossing fingers that **Bear_Nenno’**s measurements come out close to that. FWIW, if he uses a quarterfor scale , the diameter is 31/32", or a full inch, for all intents and purposes.
FWIW, I think your result is a little large. Mainly because it’s not a perfect uniform cylinder. There’s other crap on there like heat ribs, carry handle, muzzel brake, etc.
I just drove around and actually didnt come across a dishka. Funny, I could have sworn I’ve seen some scattered around here. I did find a bunch of ZPU barrels though. They fire a 14.5mm round, so the circumference should be a bit bigger, I’d think. I measured one at the muzzle and it was only 1.3" in diameter. (Using the string-wrap method and noting the string was 4 Quarter Dollars wide.)
I’ll keep my eye out for a dishka, though.
Santo Rugger - Your math skills boggle my mind. Thanks for the help. I hadn’t really thought about boring out the barrel. It’s just supposed to be a crude respresentation, so I’m not sure I’ll bother with the frustration that I know will ensue from trying to drill out something like that.
Bear_Nenno - Yes, it was the outer diameter I was looking for. A dowel is just a long cylindrical piece of wood, like you’d make a mop handle from. Thanks for looking - I appreciate that.
JSexton and puppygod - Thanks for your help.
I think I’ll go with the 1.5" or 1.75" dowel. 1.5 might be closer, but I’ll try both and see what looks better.
Thanks again, guys.