Posted: 12/19/2014 3:37:24 PM EDT
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Hi All,
I am a newbie and interested getting a bolt action soon. Anyways, my questions is that if I get a 18" barrel and put a silencer on it (let's say the silencer is 6"), does it give me the same or close to the velocity of 24" barrel? Sorry if it's a dumb question or I am beating a dead horse again. Thank you all. |
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This changes from caliber to caliber but after a certain length barrel the velocity will actually drop.
A shorter barrel will actually be more accurate, in general, because of less vibration and chance of manufacturing defects. For accuracy you want to find the shortest barrel before velocity begins to rise very slowly with length or declines. Each caliber has a sweet spot for the most velocity compared to barrel length and adding 25% more barrel to get 2% more velocity after that point makes little sense for most purposes. I had a 24'' AR15 that I cut down to 20 1/2'' because I am actually getting more velocity with the shorter barrel and the shorter barrel is more accurate. A suppressor is going to drop the velocity of a round rather than increase it, to answer your question. I gave the above info so you would realize adding barrel length may not add velocity anyway. |
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What a lovely train wreck this is!
"A shorter barrel will be more accurate" Barrel length by itself is not a determining factor when it comes to accuracy, there is a lot more that goes into that equation. "More velocity out of a shorter barrel" Assuming that nothing has changed with the load, there is physically no way to get more velocity out of a shorter barrel. "A suppressor is going to drop velocity" This could be a possibility, but a suppressor can actually decrease velocity, have no impact, or increase it, once again there are a number of factors that come into play (suppressor design, barrel length, powder burn rate, etc) to determine what will actually happen. "www.ballisticsbytheinch.com" There is some obvious value to this site, however once again, this is part of the story, but not everything that needs to be taken into consideration. The majority of this issue has already been covered here, http://www.ar15.com/forums/t_16_17/244_Short_Barreled_Precision_Rifle_Preformance_Demystified____Again.html http://www.ar15.com/forums/t_16_17/185_Thinking_about_getting_my_22_barrel_chopped_to_16___.html Per those topics, Internal Ballistics is Factual Science based on Physics & Chemistry, it is not some form of voodoo or black magic. Muzzle Velocity is a function of Powder Burn Rate (resulting pressure), Barrel Resistance (twist rate, finish quality), Payload (bullet weight & design) and Barrel Length. Those variables must all be taken into consideration together to determine what the ultimate outcome will be. Sorry, but there is much more to it than a simple yes or no answer. The simple answer would be NO, you will not get the same muzzle velocity from a 18" Barrel with a 6" Suppressor as a 24" Barrel, however by changing variables within the equation, you could potentially come close to it. Of course that would not be an Apples to Apples comparison/situation. Best of Luck, M Richardson |
Damn good answer!
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For every inch of Bbl you add or subtract you will add or subtract {aprox} 25-35 ft/sec velocity. A silencer, compensator, flash hider, etc. is not bbl adding or subtracting velocity.
Ammo needs to be loaded to lower than 1124 ft/sec to be used with a suppressor. otherwise, the sonic crack defeats the purpose. Smart question. |
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Quoted:
For every inch of Bbl you add or subtract you will add or subtract {aprox} 25-35 ft/sec velocity. A silencer, compensator, flash hider, etc. is not bbl adding or subtracting velocity. Ammo needs to be loaded to lower than 1124 ft/sec to be used with a suppressor. otherwise, the sonic crack defeats the purpose. Smart question. You DO NOT have to run subsonic ammo to get benefits from a suppressor. Having a 7mag that sounds like a 22 and recoils like a 243 is a prime example. |
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Quoted:
For every inch of Bbl you add or subtract you will add or subtract {aprox} 25-35 ft/sec velocity. A silencer, compensator, flash hider, etc. is not bbl adding or subtracting velocity. Ammo needs to be loaded to lower than 1124 ft/sec to be used with a suppressor. otherwise, the sonic crack defeats the purpose. Smart question. That last part is not true at all. |
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Quoted:
For every inch of Bbl you add or subtract you will add or subtract {aprox} 25-35 ft/sec velocity. And what particular factual data would you like to base that on? This may be true for a single set of variables, however I can easily produce multiple examples where those numbers would be no where close to accurate or real world. A silencer, compensator, flash hider, etc. is not bbl adding or subtracting velocity. Depending on the barrel length, powder burn characteristics, and the suppressor design, there are a number of situations where by adding a suppressor, you can increase muzzle velocity. Adding the confining body of the suppressor can add more time for powder to burn, and allow more time for gasses to accelerate the bullet. This is both a factual scientific argument, as well as a real world documented result. Ammo needs to be loaded to lower than 1124 ft/sec to be used with a suppressor. otherwise, the sonic crack defeats the purpose. That may be true, however probably more than 70% of rifle suppressors employed are used with supersonic ammo. There are only a handful of rifle rounds that make any sense or work very effectively if loaded to subsonic specs. Smart question. Sorry no disrespect intended, but throwing statements around as if they are the sole gospel when that is not the case, is not really helping the cause! M Richardson |
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Quoted: That last part is not true at all. Quoted: Quoted: For every inch of Bbl you add or subtract you will add or subtract {aprox} 25-35 ft/sec velocity. A silencer, compensator, flash hider, etc. is not bbl adding or subtracting velocity. Ammo needs to be loaded to lower than 1124 ft/sec to be used with a suppressor. otherwise, the sonic crack defeats the purpose. Smart question. That last part is not true at all. |
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You can throw numbers around all you want, but unless you want to qualify them, then you are throwing something around that may have little factual significance.
I can show you examples where adding or removing 1" of barrel length can impact muzzle velocity by as little as 5 FPS to as much as 50 FPS. Why is that the case? Powder Burn / Consumption Rates vary greatly, and they will ultimately dictate what the numbers are going to be. Take an Internal Ballistics Program like Quickload (http://www.neconos.com/details3.htm), and by altering the variables (Load Specs, Powder, Barrel Length) you will see how they impact the results. .308 / 175 SMK / 44 Grains of Varget. Barrel Length = FPS 16 = 2,432 / 18 = 2,502 / 20 = 2,561 / 22 = 2,613 / 24 = 2,659 / 26 = 2,700 / 28 = 2,737 / 30 = 2,770 / 32 = 2,800 NOTE - on the short end you are gaining/loosing 60-70 FPS for every 2 inches of change, but on the long end you are only gaining/loosing 30-40 FPS for every 2 inches of change. The change is NOT linear, it is exponential based on the Powder Burn / Consumption Rates, where they are sub-optimal, where they are maxed out. If you run a range of slow & fast burning powders through that program, changing barrel lengths, you will quickly figure out what the numbers really look like. You will also quickly figure out that a lot of the numbers that are thrown around like Gospel, have no real basis. Likewise throwing out numbers for suppressors is a SWAG unless you want to qualify them. Looking at muzzle velocity numbers for a Full Size Suppressor on a 24" .300 WM rifle, is going to be completely different than looking at numbers for a Mini Suppressor on a 11.5" .223 rifle. I can easily show real world examples where adding a suppressor had zero impact on muzzle velocity, to situations where it increased it by as much as 50 fps. NOTE - in MOST cases the changes are a very small overall percentage, so in the big picture the changes will have minimal impact. Yes you can look at some averages, which may work for some situations, but you should also make sure that you are NOT just taking something as being fact when it may just be fiction. As the saying goes, "The Devil is in the details". Best of Luck, M Richardson |
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@BoxofRox, Gentleman4561: Thank you very much for your response, it's just great.
@ All others: I tremendously appreciate that you took the time to write up and passing information to all of us. There are great information in your posts and I'm sure that it would help some guys out there as well. |