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Barrel Length 300 win Mag

 
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  #15  
Old 01-05-2012, 08:32 AM
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Join Date: Dec 2010
Posts: 183
Re: Barrel Length 300 win Mag

This is from well known maker Charlie Sisk:

For a long time I have wondered about how barrel length affected velocity. I had always been told you need a certain length barrel for certain calibers. I have read when folks compared one gun to another with different lengths but I always thought that was not an apples to apples comparision. So I did a few test myself.
All these were Shilen barrels. I used the same brass through out the whole test. All weighed to with 1 grain. Bullets were tested on the Juenke machine. Powder charges were weighed to .1 grain. The same rest, chronograph, Redding press, primers all from the same lot, bullets for the same box, same lathe, same crowning tool, same cutoff tool, and each rifle done from start to finish on the same day. Ambient temperature was the same because I shoot from inside the shop. I held the rifle the same way on the rest every time. I shot ten rounds first to break in the barrel. Then cleaned with Sweets and fired one fouling shot. Then shot five rounds and took the average. I used a midrange load fron the Nosler book, not too hot but certainly not a reduced load. Here is what I got.

22-250 Hodgdon 380 34 grains Federal GM210M Remington brass 55 grain Ballistic Tip
27 inches 3469 fps
26 3451
25 3425
24 3407
56 fps from highest to lowest

270 Winchester Hodgdon 4350 54 grains Federal GM210M Winchester brass 130 grain Sierra
27 inches 3115 fps
26 3093
25 3071
24 3054
23 3035
22 3027
21 3001
114 fps from highest to lowest

300 Winchester mag Federal GM215M Winchester brass 74 grains of Reloder 22 180 grain Partition
27 inches 3055 fps
26 3031
25 3024
24 3003
23 2984
22 2960
95 fps from highest to lowest

340 Weatherby Federal GM215M 250 grain Sierra
81 grains Reloder 22 Wby brass
27 inches 2837 fps
26 2817
25 2809
24 2791
23 2777
22 2755
21 2731
106 fps from highest to lowest

I think I will do a little more thinking before I recommend a barrel length in the future. What do you folks think ?
Charlie
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  #16  
Old 05-27-2012, 04:52 AM
Junior Member
 
Join Date: May 2012
Location: Eeeeek Nz
Posts: 11
Re: Barrel Length 300 win Mag

Awesum test that's what I recon!!
I love people doin a no nonsense comparison like this, good post
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  #17  
Old 05-27-2012, 09:58 PM
Gold Member
 
Join Date: Apr 2009
Posts: 892
Re: Barrel Length 300 win Mag

Quote:
Originally Posted by sakoluvr View Post
This is from well known maker Charlie Sisk:

For a long time I have wondered about how barrel length affected velocity. I had always been told you need a certain length barrel for certain calibers. I have read when folks compared one gun to another with different lengths but I always thought that was not an apples to apples comparision. So I did a few test myself.
All these were Shilen barrels. I used the same brass through out the whole test. All weighed to with 1 grain. Bullets were tested on the Juenke machine. Powder charges were weighed to .1 grain. The same rest, chronograph, Redding press, primers all from the same lot, bullets for the same box, same lathe, same crowning tool, same cutoff tool, and each rifle done from start to finish on the same day. Ambient temperature was the same because I shoot from inside the shop. I held the rifle the same way on the rest every time. I shot ten rounds first to break in the barrel. Then cleaned with Sweets and fired one fouling shot. Then shot five rounds and took the average. I used a midrange load fron the Nosler book, not too hot but certainly not a reduced load. Here is what I got.

22-250 Hodgdon 380 34 grains Federal GM210M Remington brass 55 grain Ballistic Tip
27 inches 3469 fps
26 3451
25 3425
24 3407
56 fps from highest to lowest

270 Winchester Hodgdon 4350 54 grains Federal GM210M Winchester brass 130 grain Sierra
27 inches 3115 fps
26 3093
25 3071
24 3054
23 3035
22 3027
21 3001
114 fps from highest to lowest

300 Winchester mag Federal GM215M Winchester brass 74 grains of Reloder 22 180 grain Partition
27 inches 3055 fps
26 3031
25 3024
24 3003
23 2984
22 2960
95 fps from highest to lowest

340 Weatherby Federal GM215M 250 grain Sierra
81 grains Reloder 22 Wby brass
27 inches 2837 fps
26 2817
25 2809
24 2791
23 2777
22 2755
21 2731
106 fps from highest to lowest

I think I will do a little more thinking before I recommend a barrel length in the future. What do you folks think ?
Charlie
Can't argue a well conducted experiment.
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  #18  
Old 05-28-2012, 07:48 AM
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Join Date: Jun 2010
Location: greenwood, IN
Posts: 3,544
Re: Barrel Length 300 win Mag

what's more to add to this is that the shorter barrels with the same profile will tend to group tighter due to barrel stiffness alone. Then to further add to this is that one could have gone with a slightly faster powder burn, and probablt got back a little bit of the 100fps or so lost. I went from a 26" barrel in .223 to a 20" barrel in .223, and lost about 74fps. But the rifle had a very good balance shooting off hand and the groups probably did tighten up as well.
gary
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  #19  
Old 05-28-2012, 05:52 PM
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Join Date: Dec 2005
Posts: 2,114
Re: Barrel Length 300 win Mag

Quote:
Originally Posted by Trickymissfit View Post
Here's something to think about; with a #7 contour barrel 26" long (that's a pretty heavy barrel) verses the same exact barrel 21", the 21" barrel is right at 2.75 times more ridgid.
How did you compute that 2.75 times stiffer? I don't think its resonant frequency will be 2.75 times higher.

And where can I get a #7 barrel contour dimensions so I can run my own barrel stiffness software on it?

Thanks
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  #20  
Old 05-29-2012, 06:54 AM
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Join Date: Dec 2005
Posts: 2,114
Re: Barrel Length 300 win Mag

Quote:
Originally Posted by Bart B View Post
And where can I get a #7 barrel contour dimensions so I can run my own barrel stiffness software on it?
Using Lilja's 27 inch No. 7 contour dimensions from Lilja's web site, here's what my software calculated for those two 30 caliber barrel lengths before chambering:

No. 7 contour shortened to 26 inches vibrates at 58.40 Hz.

No. 7 contour shortened to 21 inches vibrates at 90.67 Hz.

To me, that's only a bit over 55% stiffer, not 275% stiffer.

Chambering makes them a bit more flexible 'cause metal's been removed at their back end.
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  #21  
Old 05-29-2012, 12:05 PM
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Join Date: Jun 2010
Location: greenwood, IN
Posts: 3,544
Re: Barrel Length 300 win Mag

Quote:
Originally Posted by Bart B View Post
How did you compute that 2.75 times stiffer? I don't think its resonant frequency will be 2.75 times higher.

And where can I get a #7 barrel contour dimensions so I can run my own barrel stiffness software on it?

Thanks
Dan Lilja did a paper on the subject a few years back. His method of figuring the deflection was somewhat crude, but still reliable. Later I discussed this with Dan over several emails and he went further into his feelings. How much my groups did actually tighten I simply cannot confirm, but they did. I also did a complete rechamber at the sametime, and Dan felt that a good bit of the groups tightening up was from that alone. I'm certain Dan was spot on, but we're talking 4.25" groups down to .50". My guess is that I gained about .20" from barrel regidity alone. This would be an interesting test should somebody have a good and strait barrel that was 26" or more longer with no loose spots in the bore. (I don't think you can compair two different barrels in the same caliber). Later in I did my own test with a piece of 1" diameter 17PH-4 steel that I had the bore gun drilled to .250" for another project. I used a simple ten pound weight, and checked it every two inches. I saw similar results in that the closer I got to the anchoring point the stiffer the barrel was. The amount for the weight was just a guess, and something I happened to have laying around (a 10lb. piece of Mallory Metal)
gary
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