M
marion packett
Guest
Has there been any test to determine barrel length for maximum velosity?
C
Cheechako
Guest
Dragman - Do yourself a favor. Delete your post ASAP. You are sitting on the end of a tree limb and others are sawing it off, as we speak.
JMHO
Ray
JMHO
Ray
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4Mesh
Guest
Hope we're not far off the ground cause I think I'd be on the same limb as Dragman.
C
Cheechako
Guest
OK, I will quote dragman. He said, ". . . anything more (than 27-29) you will start to lose velocity . . ." So, you guys stick by that statement??
Ray
Ray
dragman
New member
I think that is about right. a 29" will have more muzzle velocity than the 30. I personally have a 6.5X284 with a 30" barrel and my friends with a 27" barrel with the same load has me by 35FPS.
C
Cheechako
Guest
Hmmm. Anecdotal at best.
Let's look at readily available test results from a reliable source. Velocity vs. Barrel length with the plain old 30-06, conducted by Springfield Armory:
24" - 2709 fps
28" - 2776
30" - 2833
32" - 2848
They stopped at a 32" barrel because that was the longest they had available.
So, are you telling me that if you cut 3" off of your 30" barrel you'll gain velocity? I don't think so.
Ray
Let's look at readily available test results from a reliable source. Velocity vs. Barrel length with the plain old 30-06, conducted by Springfield Armory:
24" - 2709 fps
28" - 2776
30" - 2833
32" - 2848
They stopped at a 32" barrel because that was the longest they had available.
So, are you telling me that if you cut 3" off of your 30" barrel you'll gain velocity? I don't think so.
Ray
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dragman
New member
Well sir you can't use a 30-06 to make your argument. different calibers and charges react differently, and bullet weight and caliber do make a difference as well as rate of twist. I know what I own and I know what it does through my chronograph. Look at what you posted the gap in speed the bullet gains gets smaller and smaller hense eventually it will go the other way the 30-06 from 24-32" may react that way while a 6.5X47 lapua doesn't
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Jeez guys. It's pretty simple. When the gas pressure is less than the force of friction, velocity drops off. With a .22 long rifle, that's around a 16-inch barrel. With a .308 (the NATO round), you're still gaining a few fps after 36 inches. Go back to the old, old thread where Jackie tested the 6BR. At 30+ inches of barrel, he was still picking up a few fps per inch of barrel.
If we can drop the grandiose claims about about at just what point velocity drops & talk about "is it worth it" we'll reach agreement much faster.
If we can drop the grandiose claims about about at just what point velocity drops & talk about "is it worth it" we'll reach agreement much faster.
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mike in co
Guest
and as you pointed out that is apples to oranges.....you dont have his bbl, he does not have yours....so it is not valid.
now take your bbl and cut it off to 27....that is if you truely believe what you posted. you will have less weight and will have gained velocity...put your money where your mouth is....
ps i ran numbers in quickload..and you GAIN velocity in 6.5x47 from 27 to 30 inches.....
mike in co.
now take your bbl and cut it off to 27....that is if you truely believe what you posted. you will have less weight and will have gained velocity...put your money where your mouth is....
ps i ran numbers in quickload..and you GAIN velocity in 6.5x47 from 27 to 30 inches.....
mike in co.
dragman
New member
Well after a few hundred more rounds I will be cutting my barrel down and rechambering it due to throat wear I will compare chronograph numbers then.
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4Mesh
Guest
Ray,
I stick by the spirit of his statement which is basically, there is a point where velocity gain is negligible, and if you go way over length, then I suppose it may drop off.
If you take your own figures posted above, you see that for the first 24" of barrel, you get almost 1000% more velocity per inch than you do for the next inches. And, folowing that, I think you'll see he's right at a certain point not far past 32" in your case.
24 2709 112.875
28 2776 16.75
30 2833 28.5
32 2848 7.5
I'll tell you what you do gain though, you gain heat in the bullet, and heat in the barrel. There's more friction. Now, after getting 116fps per inch for the first 24, I might cut my losses when the next 8" get me a total of 140. Especially if it were all at $20/inch as most barrel makers seem to ask. (admit that is past 28).
I stick by the spirit of his statement which is basically, there is a point where velocity gain is negligible, and if you go way over length, then I suppose it may drop off.
If you take your own figures posted above, you see that for the first 24" of barrel, you get almost 1000% more velocity per inch than you do for the next inches. And, folowing that, I think you'll see he's right at a certain point not far past 32" in your case.
24 2709 112.875
28 2776 16.75
30 2833 28.5
32 2848 7.5
I'll tell you what you do gain though, you gain heat in the bullet, and heat in the barrel. There's more friction. Now, after getting 116fps per inch for the first 24, I might cut my losses when the next 8" get me a total of 140. Especially if it were all at $20/inch as most barrel makers seem to ask. (admit that is past 28).
M
marion packett
Guest
I'll rely on Quick load until some one test by cutting 1" off at a time. Thanks for the response
I believe there were test done in P.S. magazine, can't remember what year but it has been done. Myself I like a little longer barrel so when it starts throwing shots I can start all over again. And I have one that started at 36 inches with over 4000 rounds that still shoots but it's a 30 Cal. What you are looking for is Optimum velocity don't care what the length is.. At 36" the velocity was 3080 and at 30'' It still will go 3080 with different powder. Was using R-22 now H-4350. So I guess if you change a few thing like I did you can still maintain your speed.
Joe Salt
Joe Salt
Just for fun I ran numbers in QL, changing only barrel length, for a 6.5x284 using H4350.
26" = 2940fps
36" = 3147
56" = 3390
106" = 3680
107" = 3684
At 270" you just break 4000fps
That barrels DROP in velocity beyond normal lengths, is WRONG.
That different barrels compared, 'seem' to counter this, is meaningless.
26" = 2940fps
36" = 3147
56" = 3390
106" = 3680
107" = 3684
At 270" you just break 4000fps
That barrels DROP in velocity beyond normal lengths, is WRONG.
That different barrels compared, 'seem' to counter this, is meaningless.
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4Mesh
Guest
You numbers from quickload are way way way more optimistic than the data from the actual test above. According to quickload, you'll keep gaining from 36-56 at a rate ~60% better than was shown in an actual test from 30-32" with an 06. I'm sure quickload doesn't account for variables found on a barrel lengh that will never exist. If I use the results from the real world testing above as a guide, and add that up with my own personal experience which mirrors it, that doesn't speak well for these estimates from 36" up.
I really don't care which is the truth. Bottom line is, extra barrel length buys you a rechamber or two, and that's about it. For all practical purposes, barrel lengths >28" are for weight, not velocity, unless you're using super slow powders not used in the 6mm the Op has. Powders that give extra velocity past 30" are usually found in big hunting guns, and are not notorious for being accurate at a BR level for 1K shooting.
I really don't care which is the truth. Bottom line is, extra barrel length buys you a rechamber or two, and that's about it. For all practical purposes, barrel lengths >28" are for weight, not velocity, unless you're using super slow powders not used in the 6mm the Op has. Powders that give extra velocity past 30" are usually found in big hunting guns, and are not notorious for being accurate at a BR level for 1K shooting.
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One from colume B:
I have seen in print -- only a little better than "what some guy said" -- that barrels using high-intensity chamberings erode some at the muzzle end, too. This from some testing the old Blackstar company had done. They had the test data, but no explanation of why.
Now if that's correct, to set your barrel back for 300 Weatherby etc., you'll have to take some off the front as well.
I wonder how hard it is on a chambering reamer when you run it into a worn barrel to set it back? I'm reminded of the guy who took such large steps to save wear on his $40 shoes that he split his $80 pants.
I have seen in print -- only a little better than "what some guy said" -- that barrels using high-intensity chamberings erode some at the muzzle end, too. This from some testing the old Blackstar company had done. They had the test data, but no explanation of why.
Now if that's correct, to set your barrel back for 300 Weatherby etc., you'll have to take some off the front as well.
I wonder how hard it is on a chambering reamer when you run it into a worn barrel to set it back? I'm reminded of the guy who took such large steps to save wear on his $40 shoes that he split his $80 pants.
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4Mesh
Guest
Kay,
What was said above about a rimfire bbl length? Where does it STOP going faster, and start going slower?
Hundreds of years ago, many hundreds, they figured out that longer barrels on canon aboard ships did NOT do anything but make the ship slower and heavier. Are you suggesting that WE are not smart enough hundreds of years later, after being beaten on the head with the answer that we STILL can't figure that out? "On our own".
Above, using test data supplied, From 24" at >110fps/Inch, you go from 30-32" and gain 7.5fps/Inch. What part of that don't you get?
I don't give a ___ if it gains .0001fps. I'm going to melt the lead in the bullet if I keep burnishing it down the barrel. The bullet grows as it gets hotter. IT WILL EVENTUALLY SLOW OR COME APART. Ever seen that happen?
Regardless of the speed-up/slow-down factor that is painfully obvious to all the rest of us. If you're shooting a 6mm that burns all it's powder in 24" of barrel, you are not going to make yourself more competitive by adding 10" of barrel. Yes, a 6x47 has lots of boiler room, and it might be able to use a powder like 4831 or R22 and send a bullet. But, I think it's been shown by about all the people who've ever shot one that that is NOT where they like to be. I'm afraid they are a few levels faster on the burn rate chart.
Ever been to a PPC match? How many 30" barreled PPC's you seen? How many 28"? Hmmm, how many 26"? 24"? Why you suppose that is? Something to do with 322 and 4227 not burning for half an hour maybe? By all means go stuff some 4831SC in a 30" PPC and show me. I've got time...
dragman
New member
Sorry for starting an arguement, I guess I mixed up what I read and what my gunsmith told me for max velocity and maximum efficency. I still don't know why the 27" barrel out FPS'ed the 30" barrel we tested with the same loads??? I still stand by there being no reason to be over 29" unless your are planning to cut set back and rechamber to save a little barrel life.