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Barrel length and velocity?

 
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  #1  
Old 04-05-2013, 11:10 PM
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Barrel length and velocity?

At what point do you start seeing diminishing returns on velocity gains with respect to barrel length with a 6.5x47? Need to make a decision on barrel length, hoping to get good velocity but not wanting an excessively long barrel that doesn't gain me any appreciable velocity.
Thanks,
Ken
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Old 04-05-2013, 11:22 PM
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Re: Barrel length and velocity?

Quote:
Originally Posted by KiloTango View Post
At what point do you start seeing diminishing returns on velocity gains with respect to barrel length with a 6.5x47? Need to make a decision on barrel length, hoping to get good velocity but not wanting an excessively long barrel that doesn't gain me any appreciable velocity.
Thanks,
Ken

Small volume cases need less barrel length to perform near there potential max velocity.

The larger the case volume and the heavier the bullet the more barrel you need.

For the 6.5x 47 24" is about ideal. 26" would about max. more barrel than 26" is in this category
(Less gain per inch).

J E CUSTOM
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Old 04-05-2013, 11:34 PM
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Re: Barrel length and velocity?

Thanks.
Ken
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Old 04-06-2013, 06:12 PM
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Re: Barrel length and velocity?

Also faster burning powders require less barrel length than slower burning barrels for greater efficiency.
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Old 04-06-2013, 07:28 PM
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Re: Barrel length and velocity?

Quote:
Originally Posted by J E Custom View Post
Small volume cases need less barrel length to perform near there potential max velocity.

The larger the case volume and the heavier the bullet the more barrel you need.

For the 6.5x 47 24" is about ideal. 26" would about max. more barrel than 26" is in this category
(Less gain per inch).

J E CUSTOM
Glad you pointed out CASE VOLUME and not CASE LENGTH. Some believe that a "short action" doesn't need a long barrel. However a WSM case would be optimized in 26+ inch barrels. Just remember the further you get away from the chamber the velocity increase will become less and less with each inch added. I'd agree that a 26 inch barrel would be the longest you'd want to go before the gains in velocity arent worth the added length and weight.
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  #6  
Old 04-07-2013, 12:42 AM
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Join Date: Feb 2012
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Re: Barrel length and velocity?

I shoot a custom 6mm rem. It has a 1:8 twist medium varmit barrel,26 inch. if i could have put a heavier barrel on it i would have, but i was limited by the stock. I think If I was to start from scratch. I would go with a heavier barrel, but leave it at 24". just not burning that much powder, plus faster powders are better in the 6.5x47
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  #7  
Old 04-07-2013, 04:04 AM
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Re: Barrel length and velocity?

In the SAAMI tests with barrels from 22 to over 30 inches and bullets in the 2500 to 3000 fps range, muzzle velocity increased about 25 to 30 fps per inch of increased length. SAAMI's web site has documents on centerfire rifle cartridges documenting this.

Unless the barrels one uses to compare muzzle velocity have the exact chamber, bore and groove dimensions as well as firing pin and ammunition properties, the velocity numbers for each length will not be good for comparison.

Exactly how does one measure or calculate the "efficiency" of a load for a given barrel?
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