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  #1  
Old 11-27-2008, 01:28 PM
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barrel length VS velocity


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Gentlemen,
Any comments concerning what direction to take when the gun you are working a load up for has a shorter barrel than what was used in the particular re-loading manual you are using. I try to compare between at least three manuals before deciding on any particular recipe. Using the 30-06 as an example. Most factory guns have a 22" barrel and most all re-loading manuals use a custom or pressure test barrel 24" in length, in that caliber. The powders that show best velocity are usually too slow for a 22"barrel. My experience tells me that slighty faster burn rate will work best for the shorter barrel, given the variables between the different bullets available and the differences between guns. Saltyreb
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  #2  
Old 11-27-2008, 02:15 PM
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For the most part, I would consider it a "given" that your going to lose some speed with a shorter barrel. Faster or slower powder won't change that.

Each rifle/load combination can be unique to itself. No fast and easy way to get there.

A full case is generaly better than one that is at 75% for most suitable powders.

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  #3  
Old 11-27-2008, 03:03 PM
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it isn't enough to get too worked up about. in fact i would not worry about it at all. the loads that produce the highest velocity in a 24" bbl will do the same in a 22" or even a 20" bbl.
the connection between bbl length and velocity is a carry over from the black powder days. you may even get higher velocities out of a 22" bbl as opposed to a 24", there are no hard and fast rules.
just load the powder and bullet you want and go hunting.
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  #4  
Old 11-27-2008, 03:10 PM
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I have two Marlin 336s I had rebarreled with 22" and 20" Douglas barrels and chambered in 307W. The headspace and chamber size are measurably identical. The 22 inch barrel shoots about 70 fps faster than the 20" barrel.
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  #5  
Old 11-27-2008, 03:18 PM
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http://www.accuratereloading.com/223sb.html
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  #6  
Old 11-27-2008, 03:22 PM
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" The powders that show best velocity are usually too slow for a 22"barrel."

Your intuitive impression of burn rate vs. barrel length is wrong. The powder that gives the highest velocity in a long barrel will also give the highest velocity in a shorter barrel. Fact.
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  #7  
Old 11-27-2008, 05:28 PM
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Ranger is correct, the fastest powder in a 24" barrel is nearly always the fastest powder in a 22" or 20" barrel.

A faster powder might be more accurate, or cleaner burning, or have less muzzle blast. But the fastest powder will nearly always be the one that fills the case completely and gives normal top pressure. If a powder fills the case completely but doesn't reach top allowed pressure, can consider that powder to be too slow for that use. If it gives top pressure but leaves unused volume, can consider that powder a bit fast for that case.

Don't get me wrong...may a fine load does not completely fill the case, but if max. vel. is your goal, finding one that does is a good place to look.

Last edited by ribbonstone; 11-27-2008 at 05:30 PM.
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  #8  
Old 11-27-2008, 06:40 PM
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Yup - you may be thinking of handgun barrels where 4" or 5" more barrel length will consume a slower burning powder a little better and give additional velocity, but for all intents and purposes, what works best in a 24" test barrel will work equally well in a 22" barrel, with maybe a 50 to 60 fps loss in velocity.

The reason some shorter barrels will have a higher velocity that a similar chambered and identical rifle with a longer barrel is that the shorter barrel is most probably smoother in bore than the longer one, which will cause a bit more friction in the longer, in addition to depth and condition of lands and grooves which will determine actual bore diameter.
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  #9  
Old 11-27-2008, 06:41 PM
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Wink Barrel Length VS velocity

Gentlemen, Thank you, it is true that with any established and tested reload, with a given set of variables I.E. altitude, temperature, batch of powder, primer used, bullet lot, weight of brass and all the variables that has the velocities documented via a chronograph, that if we continue to shorten the barrel the velocity will decrease. If a case has been filled to 100% or even a compressed load up to lets say 110% and shows not only low velocity but also signs of high pressure ,then what approach should be taken then to develop a load. Saltyreb
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  #10  
Old 11-27-2008, 07:00 PM
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Barrel length VS velocity

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Originally Posted by ranger335v View Post
" The powders that show best velocity are usually too slow for a 22"barrel."

Your intuitive impression of burn rate vs. barrel length is wrong. The powder that gives the highest velocity in a long barrel will also give the highest velocity in a shorter barrel. Fact.
Ranger, I disagree, in that a pressure curve for one powder in a certain length tube i.e. barrel is not the same in another. Example. you could not burn V20n29 in a 10" 50 cal barrel and expect the velocity to be the same in 35' barrel. Saltyreb
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  #11  
Old 11-27-2008, 07:16 PM
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barrel length VS velocity

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Originally Posted by ribbonstone View Post
Ranger is correct, the fastest powder in a 24" barrel is nearly always the fastest powder in a 22" or 20" barrel.

A faster powder might be more accurate, or cleaner burning, or have less muzzle blast. But the fastest powder will nearly always be the one that fills the case completely and gives normal top pressure. If a powder fills the case completely but doesn't reach top allowed pressure, can consider that powder to be too slow for that use. If it gives top pressure but leaves unused volume, can consider that powder a bit fast for that case.

Don't get me wrong...may a fine load does not completely fill the case, but if max. vel. is your goal, finding one that does is a good place to look.
Ribbonstone, your analysis is a good one, But I have encountered high pressure on many occasions with all the right senarios. Nothing is given with even the best thought out loads. Saltyreb
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  #12  
Old 11-28-2008, 05:34 AM
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Velocity will usually be higher in a longer barrel simply because the gas has more time and distance to accelerate the bullet. Ranger and Ribbonstone are absolutely correct.

Using a faster burn rate powder in a short barrel actually complicates the velocity loss, because faster powders have to be loaded with a lower charge weight. That lessened amount of powder produces a lower volume of gas. Lower gas volume acting across a shorter time and distance produces even less velocity.

Finally, pressure curves do not change due to the length of the barrel, except that with a short barrel, bullet exit releases the gas when it's still at a higher pressure. For the pressure curve to change solely because of barrel length, the powder would have to "know" how long the barrel is and burn differently because of it. Powder has many amazing qualities, but omniscience is not one of them.
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  #13  
Old 11-28-2008, 05:43 AM
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No doubt about it, each gun/barrel is a law unto itself and often defy conventional wisdom...you just learn what each wants and feed them their preferences.

Only once did a too slow powder suddenly show high pressure (in this case, too slow fit my defination...I wasn't supose to be able to cram enough in there to come near standard pressure). Many times too fast a powder has shown a sudden pressure jump. The odds are in favor of the slow side.

I'm a bit conservative with loading and don't seek out the last 100fps. If I've found a good accurate load at 2500fps, I don't worry about other loads that are reported to do 2600. Haven't found enough real-world difference in that 100fps.
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  #14  
Old 11-28-2008, 08:21 AM
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Barrel length VS velocity

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Originally Posted by Rocky Raab View Post
Velocity will usually be higher in a longer barrel simply because the gas has more time and distance to accelerate the bullet. Ranger and Ribbonstone are absolutely correct.

Using a faster burn rate powder in a short barrel actually complicates the velocity loss, because faster powders have to be loaded with a lower charge weight. That lessened amount of powder produces a lower volume of gas. Lower gas volume acting across a shorter time and distance produces even less velocity.

Finally, pressure curves do not change due to the length of the barrel, except that with a short barrel, bullet exit releases the gas when it's still at a higher pressure. For the pressure curve to change solely because of barrel length, the powder would have to "know" how long the barrel is and burn differently because of it. Powder has many amazing qualities, but omniscience is not one of them.
Thanks Rocky Raab, I mis-spoke concerning pressure curve, and should have stated your point concerning the way too short barrel, but you did it for me. Sometimes my questions are only meant to clarify points to the reloaders out there that are interested in the finer points of reloading or should I say its mysteries. Saltyreb
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  #15  
Old 11-28-2008, 08:29 AM
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barrel Length VS velocity

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Originally Posted by ribbonstone View Post
No doubt about it, each gun/barrel is a law unto itself and often defy conventional wisdom...you just learn what each wants and feed them their preferences.

Only once did a too slow powder suddenly show high pressure (in this case, too slow fit my defination...I wasn't supose to be able to cram enough in there to come near standard pressure). Many times too fast a powder has shown a sudden pressure jump. The odds are in favor of the slow side.

I'm a bit conservative with loading and don't seek out the last 100fps. If I've found a good accurate load at 2500fps, I don't worry about other loads that are reported to do 2600. Haven't found enough real-world difference in that 100fps.
Thanks Ribbonstone, I mispoke concerning pressure curve. Rocky Raab made my point by addressing the way too short barrel and the gas escaping while still at high pressure before peaking. I too am conservative and am not looking for highest velocity. Higher velocity only if accurate and appropriate for the bullet construction. Saltyreb
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  #16  
Old 11-28-2008, 08:42 AM
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Because peak pressure occurs in a rifle when the bullet is only an inch or two down the barrel, the only ballistic thing that improves by going with faster powders in shorter barrels is ballistic efficiency. That is a measure of the percent of energy in the powder charge that is translated to kinetic energy in the bullet. With a slow powder a shorter barrel leaves a higher percentage of powder yet to be burned at the moment the bullet exits than it will with a faster powder. The slow powder produces higher velocity, but also produces more muzzle flash and recoil. For those reasons and to economize on powder, a faster powder is often preferred for a shorter barrel, but that is not a preference designed to maximize velocity. Just to reduce cost, muzzle flash, and recoil in lighter, shorter guns. I realize that shorter doesn't always mean lighter, but the two often go together in field guns.
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Last edited by unclenick; 11-28-2008 at 08:44 AM.
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  #17  
Old 11-28-2008, 08:44 AM
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Smile barrel length Vs velocity

Thanks to all for your input and comments. I do understand that the right powder is the right powder for that particular rifle. Ideally, if the correct powder and charge are found it will peak pressure close to the back end of the barrel giving best velocity and hopefully great accuracy also. Saltyreb

Last edited by saltyreb; 11-28-2008 at 08:59 AM. Reason: Ommited the word back before end of barrel.
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  #18  
Old 11-28-2008, 09:10 AM
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Lightbulb Barrel length VS velocity

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Originally Posted by saltyreb View Post


Ranger, I disagree, in that a pressure curve for one powder in a certain length tube i.e. barrel is not the same in another. Example. you could not burn V20n29 in a 10" 50 cal barrel and expect the velocity to be the same in 35' barrel. Saltyreb
Ranger, Thanks, I certainly mis-spoke concerning pressure curve. I should have been clearer regarding using the correct powder for any particular rifle and the duration of burn concerning barrel length and its effects. I will try harder next time. Saltyreb
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  #19  
Old 11-28-2008, 02:55 PM
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Salt, you got it, that's all that matters. It do seem counter intuitive.
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