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Barrel length and powder burn rates?

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  #64  
Unread 06-09-2009, 04:38 PM
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Re: Barrel length and powder burn rates?

RR says,
"I bet you wonder why noone pays attention to your posts"

Then why are you? Looks like you just lost your own bet.

Again, it really does not matter who reads my post, my life will continue on just fine.



RR says,
"but I'm not stupid"

Now that's a bet I'll take!
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  #65  
Unread 06-09-2009, 04:48 PM
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Re: Barrel length and powder burn rates?

you've made your case, how'd it work out, looks like all you've got left is to take a personal poke, help yourself, keep quoting the guys who write in the gunrags to make a buck, but go read somemore of his stuff, its mostly a smokescreen.
RR
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  #66  
Unread 06-09-2009, 04:50 PM
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Re: Barrel length and powder burn rates?

su37
I am in the process of have a rem. 260 built. i have a 26" barrel from brux
1-8 twist. what powder would you recommend best for this caliber my bullets will be 139 lapua and some 142 gr smk's
some people told me that h1000 should be to slow
h4831sc might be not produce the velocity that h4350 will.
i just want to know what will give me the best velocity.
i will have to shoot the load to find the best accuracy.
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  #67  
Unread 06-09-2009, 05:05 PM
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Re: Barrel length and powder burn rates?

I personally burn 50 grains of RL25 in a once fired Lapua 243 case necked up to 6.5.

I get 2,790 mv behind a 140 in a 22" barrel. Longer target bullets may vary.

Works for me.


RR, I think if you call up Chub Eastman who still hangs out at Nosler and Ken Howell
who wrote the book on ballistics. I believe you will find they agree with John Barsness.
Two of many.

I'm just a dumbclutz still trying to figure it all out.
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  #68  
Unread 01-09-2017, 12:54 AM
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Re: Barrel length and powder burn rates?

Quote:
Originally Posted by AJ Peacock View Post
SU37,

In looking through my reference library to try and prove 'your' supposition, I happened upon a couple paragraphs from Julian S. Hatcher, whom certainly should need no introduction.

From pages 309-312 of "Hatchers Notebook" (pages 310-311 are pictures only), he discusses burning rates and methods to slow burning to extend the pressure as the bullet proceeds down the barrel. The following is quoted, any typos are certainly mine. I've highlighted portions that are directly relevant to our discussion.

" The great trouble with getting high velocity in a gun is the fact that when the powder in the cartridge is ignited it turns into gas, and this gas, confined in the small space of the cartridge case, creates a very high pressure which pushes the bullet along the bore of the gun. But as soon as the bullet starts to move along the bore, that leaves more space for the gas to occupy, hence there is less pressure, and the effect of the powder will rapidly fall off to nothing unless special means are taken to keep the pressure up.

One of these special means is the perforation of the powder grain, which causes it to have a larger burning surface as the combustion proceeds. This is because the primer flash ignites the inside of the tube as well as the outside of the grain. As the grain burns, the outside surface gets smaller, hence the rate of evolution of gas would burn away, and the diameter of the hole becomes larger, with a corresponding increase in the interior burning surface.

The balance between these two surfaces can be controlled by the ratio of the inside diameter to the outside diameter in the finished grain of powder. In cannon powders with their larger grains, there are usually seven perforations instead of one.

Another method of controlling the burning of the powder and making it more progressive, that is, making it holdup its pressure longer during the travel of the bullet, is by coating the powder with a substance which makes it burn slowly at first. As this coating burns off the outside of the powder, the speed of combustion increases. These progressive-burning powders tend to give a more uniformly distributed pressure, sustained longer during the travel of the bullet. Moreover, the maximum pressure is not so high because instead of being exerted all at once, the pressure is spread out more evenly during the entire travel of the bullet. The du Pont "Improved Military Rifle" powders such as I. M. R. No 3031, I. M. R. No. 4320 and I. M. R. No. 4064 are progressive powders.

Like black powder, smokeless powders are also controlled as to their speed of burning by the grain size. Powders with very fine grains burn up in a hurry and therefore are particularly suited for short-barrel weapons. Powders with very large grains take longer to burn up, and are adapted to long-barrel weapons such as cannon. ..."

The text continues to talk about granule size and ignition dynamics, but is not directly relevant to our current discussion.

I'll sit here on the same page as Julian S. Hatcher, I also suspect that Powley is sitting here beside us.


AJ
Well worthy of a quote and repeat.
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