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Posted: 8/3/2004 1:24:01 PM EDT
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Hello All! I am in the process of building my first .50 and am trying to find some information on velocity vs barrel length. I've got a 29 inch barrel right now, but the design I am leaning towards would favor a slightly shorter barrel (24 inches). I've been looking for some information to quantify the performance trade-offs but have so far struck out. Any help would be greatly appreciated... Brobee edited to add: I would be using standard .50 bmg m33 ball ammo as a reference load |
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Thank you for the link...lots of learning I've got to do over there for sure! They mention on that site that they've set 28 inches as the minimum practical length for a .50 cal. Does anyone have any experience in the 22 to 24 inch range? Can a guy reasonably extrapolate the loss in muzzle velocity based on the 20fps rule? Thanks... Brobee |
You'll be fine with the shorter barrel, you'll lose some velocity which in turn will affect how far you'll be able to shoot. Serbu uses 22" barrels for his BFG Carbine, it's a good shooting "lighter" .50. I think the UltraMag50 uses a 22" barrel also, the only thing you might here negative is from the people shooting next to you. It will be them telling you to move because they're getting pelted by unburnt powder.
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If you are going 50BMG the rig is going to be big and heavy anyway. Why limit the long range effectiveness by going to a shorter than reccomended barrel? Shorter barrel will leave you with less velocity which translated to more bullet drop (a big deal at longer ranges) and less energy delivered to the target. Energy is a velocity squared function, so the 150 fps you loose to a 24" barrel is a substantial sacrifice of energy. Plus that fireball at the end of the barrel is going to be huge! Remember 50BMG burns 220 to 250 grains of powder so shorter barrel that has 10% of that powder "in work" at the end of a 24" barrel will be a 22 grains of gun powder fireworks display at the end of your barrel! One shot in low light and you and all around you will be useless for 15 minutes. But hey, if a snubby 50BMG is what winds your clock, go for it! It will be several pounds lighter and fit in a smaller case. I sat next to a gent with a 50BMG with a 18" barrel and a silencer at an AR15.com shoot, it was quieter than a 308 Win and he was only shooting 200 yards anyway. All depends on your use I suppose. |
who needs a 50 cal for hunting? 
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"NEED" is a hard thing to prove, but if AZ-K9 wants an 18" barrel 50BMG for hunting then he should have it by God! Now if I can get him to tell me where in this desert he finds those 2 story tall Gila Monsters, maybe we can get a serious hunt going!  Take Care Guys, BillSP1 (Phoenix) |
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I plugged some numbers into my interior ballistics program and got the following results: (using similar loading to a military ball round, 647 gr. projo, 245 gr. H 50 BMG powder, Pmax=52,744 psi) 45" Barrel = 3048 fps muzzle velocity, 95.74% powder burn 36" = 2984, 93.78% 29" = 2732, 91.34% 25" = 2614, 89.31% 24" = 2580, 88.69% 22" = 2507, 87.28% 18" = 2329, 83.52% Pretty interesting numbers. I don't have much experience with 18" barrels, but our 22" barreled carbines sell pretty well, and are a lot of fun to shoot. They actually kick less than the full-sized gun, in spite of their 17-lb weight. Still plenty of punch for 99% of stuff that the average shooter wants to do with it. The muzzle blast is certainly increased, but then the muzzle blast is pretty damn obnoxious on any .50 BMG rifle, in my experience. I used to scoff at any barrel less than 29" on a .50, but now I'm a believer. Good luck on the project! Mark Serbu www.serbu.com |
If I ever get drawn for moose or brown bear, I'm gonna make it a point to use the 50 with proper ammo. If I ever get around to buying a portable 50, I'll eventually wind up deer and elk hunting with it, with the right ammo of course.
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My rifle has about a 43 inch barrel. It was made from an M2 barrel, and I didn't have the heart to cut off more than what was needed to re-thread it. It looks pretty cool. But I would lean towards 30 to 32 inch barrels for practical purposes. Anything shorter detracts from the reason I wanted a .50, for the power. Anything longer starts to cause a serious lack of rigidity in the barrel, affecting accuracy. Also. I have a theory that longer barrels get more metal fouling at the front end, as frictional heat starts to soften up the jacket material during its longer barrel time. And my 43 incher won't quite fit in my car, even when taken down. One additional point in favor of a bit longer barrel: Should you be so lucky as to wear it out from shooting, you might be able to shorten it from the breech end, re-chamber, and be back in business. Provided the barrel has enough meat in it to form the needed thread and shoulder, most of the troublesome erosion takes place within just a few inches of the chamber. If cleaned carefully, the rest of the bore probably actually improves with use. |
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