Barrel length and powder burn rates?

[J E Custom]

Well, I never thought my initial question would have sparked 7 pages of discussion. It was very informative to say the least - I learned a lot!

I think the bottom line for me is that I will keep my 26" barrel and H-1000 powder for now. If I get the accuracy I need out of that combo that is worth more than the little bit of mobility I might gain from a shorter barrel.

I wish I had the luxury of testing multiple barrel lengths with various powders to put some of these ideas through their paces. Sounds kinda fun.

In the mean time, if anyone has first hand experience (good or bad) with the combination I originally asked about, I'd be interested in your thoughts.

300 win mag
20" - 24" barrel
Slow powder (H-1000)
190gr match grade bullet

I think AJ cleared up the one issue very well so I will give you my opinion on your last question.

If you break it down to case capacity it is simple.

Cases that hold less than 50 grs of powder do well with short barrels, Because in order to reach
maximum pressures and velocities they use Fast burning powders and the gain per inch of
barrel over 20 to 22"inches is minimal .

Cases that hold less than 75 grs of powder are at there best when medium to slow burn rate
powders are used with 24" to 26" barrels 28 to30'' barrels can contribute to some increase in
velocity.

Cases that hold 75 to 100grs are at there best using slow burning powders and 26" to 30"in
barrels.

Cases that hold more than 100 grs of powder Need the slowest powders and can benefit from
30"inch + barrels . the maximum practical length that should be used is 34" inches because of
weight and performance.

The 300 win mag falls into the 75 gr group and 24" barrels would be considered the minimum
effective barrel length.

The 308,7/08 size cases work well with 18 to 20" barrels and are very portable, They like faster
burning powders like 4350,414,4064 and Varget.

There is one exception to this and it is the big bores (.375 and up ) they can burn huge amounts of
faster burning powder because of surface diameter of the bullets. But again they can and do use
short barrels.

There are a lot of cartridges that will work with 22" barrels ,and with the introduction of the short
magnums you can build a rifle that is short AND powerful,And because the short action saves
in overall length and uses less of the bore when chambered you can have a barrel 23" and have
the overall rifle length very short and handy.

I hope this answers your other question

J E CUSTOM

 

[bookworm]

Great reply JE.

Thanks for taking the time to help with my education.

 

[pressman]

i would not argue with any of you but i can say this. i don't normally ready argumentative threads. but this one has been so educational that i could not stop reading it. and if it was not for su37 being so hard headed i would not have learned what i did so all i have to say is thank you su37 you may not have learned anything but i have. so it was not a lost discussion after all.

 

[Ridge Runner]

So I guess all those fireballs I see from my 458 socom weren't really there!! because all the powder burn't 18" back towards the chamber!
RR

 

[su37]

Not trying to stir it up here by any means.

To quote John Barsness

"The same powders that produce the most velocity with a longer barrel also produce the highest velocities with a shorter barrel. This is because almost all smokeless powder burns within a short distance in front of the chamber, contrary to what you may have heard.

In fact, the least velocity loss in shorter barrels is generally with heavier bullets and the slowest powders. "

 

[su37]

"So I guess all those fireballs I see from my 458 socom weren't really there!! because all the powder burn't 18" back towards the chamber!
RR"


And to quote John Barsness again,

"Actually the ball of flame is the hot gas from the powder reigniting when it hits the oxygen of the atmosphere, not still-burning powder.

Almost all the smokeless powder in a charge, say 99% plus, is consumed within at most a few inches of the case mouth, and often a lot sooner.

Of course the load has to create about the right pressure for the powder, as various powders are designed to burn best at different pressures. When the pressure is low for the powder--as in your Varget .45-70 load--then many powder granules simply won't burn. A few stay in the bore, but most are blown out the muzzle--but they aren't burning."

 

[Ridge Runner]

"Actually the ball of flame is the hot gas from the powder reigniting when it hits the oxygen of the atmosphere, not still-burning powder.

And I bet you wonder why noone pays attention to your posts, if something is burning, and goes out then as it gets air it re-ignites, what goes on? you better look up the definition of re-ignite, nah forget it, just remember, if your house catches on fire and the FD put it out, if it re-ignites, it ain't burning, don't worry about it.

Now I don't run a nuclear reactor in my spare time but I'm not stupid, I know that powder doesn't actualy burn so to speak, neither does wood for that matter, heat converts it to gases that burn. and powder burns more violently when its under pressure, thats why you can pour a lb of powder out in the yard and watch it burn a pretty blue flame. if the gasses made by the powders ignition re-ignite, then the powder is still doing what it sposed to do which is make pressure (if it can) and your wasteing powder, by using too slow of powder for the application, if its still making pressure the gasses are burning, Ron white said it best.......it can't be fixed!
RR

 

[su37]

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!

 

[Ridge Runner]

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

 

[pressman]

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.

 

[su37]

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.

 

[WildRose]

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.