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effect of barrel length on velocity? |
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River Runner
Optics Apprentice Joined: January/24/2012 Location: Colorado Status: Offline Points: 50 |
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Posted: May/10/2012 at 05:34 |
How much effect does barrel length have on velocity? Specifically, are hand gun rounds a lot faster, and therefore more potent, when used in a carbine?
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Randy
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8shots
Optics Jedi Knight Lord Of The Flies Joined: March/14/2007 Location: South Africa Status: Offline Points: 6253 |
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A longer barrel gives the propellant more time to burn, therefore a greater velocity being achieved. That is normally the case, all things being equal. But all things are not equal. Given a rifle barrel, speed increases by around 40-100 ft per sec for every inch added, but only up to a point, around 40 inches or so, then it would actually slow down.
I would imagine bullets loaded for pistols etc are loaded with a smaller charge, therefore the slowing down process could happen at a much shorter barrel length. What that length is, I cannot help you.
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Bigdaddy0381
MODERATOR Georgia peach Joined: February/27/2007 Location: Georgia Status: Offline Points: 13680 |
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all depends in powder used, bullet used, and caliber. a .223 will be really close 20fps in a 24 or 18 inch barrel with a 55gr bullet. now a 338rum and a 300gr bullet will vary 200 fps or more in a 18 to 30 inch barrel.
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Rancid Coolaid
MODERATOR Joined: January/19/2005 Location: United States Status: Offline Points: 9318 |
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I would be VERY surprised to see a rifle round gain 100 FPS per inch added. In cutting down many 308s and 300WMs, I see usually between 25-50FPS loss, depending on barrel. Custom barrels, for me at least, lose a little less, factory lose a little more. Good question about the carbines, I have only recently started playing with a 40 S&W AR with an 11" barrel, but haven't chronoed any loads yet. If it gains, it ain't 25-50 FPS, I would guess.
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Bigdaddy0381
MODERATOR Georgia peach Joined: February/27/2007 Location: Georgia Status: Offline Points: 13680 |
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from my reloads on a 500S&W the barrel length plays a roll in it from the snub to the 6 or what ever I have. My guess is 41gr of powder don't burn completely in ether just more so in the longer barrel. I'll see if I can dig up the test data I have on them.
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3_tens
Optics Jedi Master Joined: January/08/2007 Location: Oklahoma Status: Offline Points: 7853 |
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Bullberry barrels has tested their barrels with different calibers with 1" length drops. Here is a link to the test on the 17 HMR that held the highest velocity with a 19" barrel. Accuracy improved as the barrel was shortened. The lengths tested ranged from 22" down to 11"
http://www.bullberry.com/HMRdata.html |
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3_tens
Optics Jedi Master Joined: January/08/2007 Location: Oklahoma Status: Offline Points: 7853 |
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When loading pistol ammunition for a rifle the best results are achieved by using slower powders in the rifle. When charging the ammunition differently for a rifle, is important not to mix the ammunition between weapons. Extreme care should be exercised not to fire the rifle specific shells in a handgun.
Some reloading manuals have tables that will list pistol and rifle loadings separate. Other publishers are too fear that there could be mix ups and only list the pistol loadings. |
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Folks ain't got a sense of humor no more. They don't laugh they just get sore.
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supertool73
Optics God Superstool Joined: January/03/2008 Status: Offline Points: 11814 |
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I recently had a new rifle built. I had a obermyer barrel put on it and had it cut 19" from the recoil lug.
I worked up a load and after I found an accurate load I chronoed 40 rounds. I was averaging 2641. I was really shocked to see that kind of velocity, I figured mid 2500s is where I would be. Initially I thought something must be wrong with my chrono. But I just got back from a 4 day rifle class and my data matched up with my velocity. My cousin shoots a 700 5r milspec with 24 inch barrel, we shoot virtually the same load. All the way out to 1000 yards I was always needing less elevation than he was to make the same hits. |
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8shots
Optics Jedi Knight Lord Of The Flies Joined: March/14/2007 Location: South Africa Status: Offline Points: 6253 |
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I think that the chamber cut also plays a role. A tight matchgrade chamber and barrel combo would chrono faster then a loose.... wait this sounds all wrong. But I'm sure you get the drift???
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stickbow46
Optics Master Extraordinaire Joined: January/07/2009 Location: Benton, Pa Status: Offline Points: 4678 |
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Recently there have been several LE agencies that have switched over to a 18" barrel for their 308 sniper rifles Many have started wih a 26" barrel & cut 1" off at a time till they got down to the 18" mark which had the same & better accuracy as the longer barrels.I personally have found this to be true with my Rem 5r .308.
I just purchased another Rem SS 5r mil spec in 20" barrel,this came directly from Remington,cut & threaded with a cap to cover the threads.Point being Remington must be thinking that smaller is better. On a side note ,best length for a .22lr is 16" as it runs out of powder at that point. Edited by stickbow46 - May/11/2012 at 02:47 |
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Kickboxer
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stickbow46
Optics Master Extraordinaire Joined: January/07/2009 Location: Benton, Pa Status: Offline Points: 4678 |
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Very good article,Thanks KB
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silver
Optics Master Joined: November/04/2005 Location: United States Status: Offline Points: 2291 |
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Pistol rounds depend on the a lot on the rounds. The .45acp does not gain a lot, the powder normally used is to fast. A 9mm or .357 that likes a slower powder gains alot with a longer barrel.
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koshkin
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stickbow46
Optics Master Extraordinaire Joined: January/07/2009 Location: Benton, Pa Status: Offline Points: 4678 |
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Good sight Thanks Ilya
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