Varget running out of barrel?

Farlsincharge

Farlsincharge

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Finally got my xcr compact tact out today with a pile of load development to commence. I had some varget pushing 55 gr sierra's. 26.5gr and 27 gr had absolutely no difference in velocity. .5 grain usually equals ~50 fps in my experience . Is it possible that varget doesn't have enough time to burn completely in 20" once it is loaded this heavy? The chrono doesn't lie and I thought this result was fairly funny.
any insight?
 
Varget is a slow burn so it is very likely your rounds are leaving the barrel by the time those extra kernals are producing pressure...also, varget is great for heavy bullets above 65 gr. and not so much under...imho
 
I have had good luck with 4895 and benchmark. Just always pushing for more velocity led me to varget. I just found it kind of neat that the velocity gains actually stopped at a certain point.
 
Farlsincharge said:
Finally got my xcr compact tact out today with a pile of load development to commence. I had some varget pushing 55 gr sierra's. 26.5gr and 27 gr had absolutely no difference in velocity. .5 grain usually equals ~50 fps in my experience . Is it possible that varget doesn't have enough time to burn completely in 20" once it is loaded this heavy? The chrono doesn't lie and I thought this result was fairly funny.
any insight?
Click to expand...

MV's do not increase linearly as powder charges increase. It's not at all unusual for a 0.5 or even 1.0 grain increase in powder to not produce an increase in MV on a given day - I've seen it many times, as recently as yesterday, and have even seen decreases, and with many different powders, chamberings and barrel lengths (which is a Red Herring). If you had carried on with higher loads, you would have seen the MV increase, and probably more situations like the one you encountered.

All powders are completely burned within 2-3 inches of the chamber, Varget, and much slower powders than Varget included. There is still usable pressure that can accelerate the bullet available, but the powder has all been converted to heat and the products of the combustion. It is a common myth that the slower the powder, the longer the barrel that's required - this is nonsense. If this was not true, wouldn't powder manufacturers provide load data that differentiates between short and long barrels? Since more of a slower powder can be used, you will produce or lose more MV per inch of barrel, but more of a slower powder will always produce a higher MV than less of a faster powder, regardless of barrel length.

P.S. Chronys do "lie", in that they are not perfect. They all have a margin of error that can be up to +/- 1% depending on conditons - that can translate to +/- 20 fps.
 
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Go to 6mmbr, click on .223. They have a section and loads specifically for ar type rifles. I have been having excellant results with H335. It seems to burn clean and as a ball powder it drops within 1/10grain. I don't find any leftovers out of my 10 1/2 LMT.
 
Andy said:
All powders are completely burned within 2-3 inches of the chamber
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Not even close. Pressure peaks about 1.5-2" from the chamber, but power continues to burn. It's the rare load that burns all the powder before the bullet leaves the barrel.

For example, 75gr bullet in .223 with a typical load of 4895 leaves about 5% of the powder unburned in a 20" barrel.

This is most evident when shooting pistols - some loads produce a lot of ejecta, so much that you can sweep the range and ignite the sweepings.
 
First off, the phenomenom that you describe has nothing to do with barrel length which is/was the theme of this thread. Secondly, it comes down to what is meant by "completely burned".

All powders create heat (and from that pressure), as well as combustion by-products which can be fine soot if the pressure is right for that to happen for that powder, course granules ("crinklers"), at lower pressures, and finally clumps of unburnt powder if the pressure is low enough. This will happen regardless if it's a 4" or 40" barrel, as it's the pressure that dictates it. Those by products will all burn some more if collected from the bore, but they had done all the burning that would produce pressure very close to the cartridge mouth, right where the pressure curve had peaked. What I mean by "completely burned within 2-3 inches of the chamber" is that all the powder that can be converted to pressure will have done it by then.

Quickload will calculate "Propellant Burnt %" which is where I assume you got the 5% (inverse of 95%) figure. You will notice in the chart below, that there is a critical pressure under which not all of the powder will be consumed, but again, it is not dependant on barrel length.

QuickLoad_PowderCh2.png


Note that for the example above (using Varget, but not in a 223), that a 100% burn doesn't occur until you're at an over-pressure situation. Bullseye will get a "100% burn" at a much lower pressure than will US869, but again, neither are still "burning" 20 inches from the boltface.

Semantics perhaps, but the fact remains that there are not powders that are "tuned" to certain barrel lengths, they are only tuned to relative burn rate and operating pressure range.
 
Andy said:
All powders are completely burned within 2-3 inches of the chamber, Varget, and much slower powders than Varget included. There is still usable pressure that can accelerate the bullet available, but the powder has all been converted to heat and the products of the combustion.
Click to expand...

If everything is burned and has produced 'X' volume of gas within 2-3" we would theoretically see no difference in velocity between a 10" and a 20" rifle. (if you factored out the additional drag of the bullet in the last 10" of barrel, it is theoretically worse in the 20"...)
Is this what you are suggesting?


Andy said:
It is a common myth that the slower the powder, the longer the barrel that's required - this is nonsense.
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Maybe in theory, but not in practice. You need to compare the same platform of each with different barrel lengths with the same ammunition.
(ie. Compare that same heavy gr. bullet with varget load in a 10" and a 24" AR and you are going to see a world of difference - not theory, REALITY:D)

Andy said:
If this was not true, wouldn't powder manufacturers provide load data that differentiates between short and long barrels?
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Ummmmm, they do!!! They give their data along with what they shot it through. Variables change and the gun and barrel is a huge variable on load data ;)....
 
I'll try once more, and spell it out more clearly and undo the words you tried to put in my mouth. Pointless for you I'm sure as you will cling to what you said, but others might benefit.

When did I talk about volume of gas? Heat produces the pressure. Pressure is decreasing, but volume is increasing and will continue to increase until the pressure level lowers to atmospheric pressure. That would likely take several feet of barrel to occur, but eventually the gains turn into losses due to bullet-bore friction - tests have shown that's usually at about 40". You will again misinterpet this.

Of course a 10" barrel will produce lower MV than a 24", regardless of the powder. Many tests have been done where barrels were cut and a variety of powders used, and it always showed that at equal pressures, more of a slower powder always produce higher MV's than less of a faster powder, regardless of barrel length. Here's where practice agrees with theory.

This is where it gets humourous. Ammo manufacturers state barrel length so that you can compare expected MV's with their stated barrel length, with the length of your own barrel. If the table is for a 26" barrel and you have a 22", you should expect lower MV's. What powder manufacturer provides multiple tables for different barrel lengths for the same round? "Use this powder with these barrel lengths only" Show me.
 
Andy said:
This is where it gets humourous. Ammo manufacturers state barrel length so that you can compare expected MV's with their stated barrel length, with the length of your own barrel. If the table is for a 26" barrel and you have a 22", you should expect lower MV's. What powder manufacturer provides multiple tables for different barrel lengths for the same round? "Use this powder with these barrel lengths only" Show me.
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Load data exists to keep the peak pressure below the maximum SAAMI pressure. The peak pressure is achieved in the first couple of inches of bullet travel, regardless of whether you're correct about all powder burning within the first few inches or not. The fact that there is no load data for different barrel lengths is not evidence either for or against your claim of all the powder burning in the first few inches. If you're right, there's no powder burning to increase the pressure after the first few inches, so you don't need different load data for different barrel lengths. If you're wrong, any powder burned after the first few inches is burning after the pressure has peaked, so it can't reach a higher pressure later that exceeds SAAMI specifications, so you don't need different load data. The point you're trying to make here seems like a red herring.
 
I suggest that most of you except Andy read an old SPEER loading manual or pehaps one of the Hornady manuals. There are many things that influence pressure, and bullet seating depth, crimping, powder type (single or double base) and shape (ball, flattened ball, flake, extruded etc) along with primer type all play a part. So does barrel length to some extent, but there is minimal difference between 22, 24, & 26 inch barrels. Bullet depth will actually increase pressure (touching the lands vs getting a short "running" start) more than barrel length.
Igniting the powder causes it to flagrate - aka "burn very rapidly". This causes huge amounts of gas to be created (which creates pressure) and when this gas is heated from the burning powder the gas volume increases creating peak pressure. And all this happens very fast. Then the bullet exits the barrel and the pressure and temperature drop back to normal. (of course it takes longer for the heat to dissipate than the pressure)
However, my friends, all the powder is burned up almost immediately (aka - in the first couple inches of bullet travel). What you see in the snow are the by-products of combustion. But it sure isn't unburned powder. (talking rifles here, not revolvers)
 
Bigbubba said:
I suggest that most of you except Andy read an old SPEER loading manual or pehaps one of the Hornady manuals. There are many things that influence pressure, and bullet seating depth, crimping, powder type (single or double base) and shape (ball, flattened ball, flake, extruded etc) along with primer type all play a part. So does barrel length to some extent, but there is minimal difference between 22, 24, & 26 inch barrels. Bullet depth will actually increase pressure (touching the lands vs getting a short "running" start) more than barrel length.
Igniting the powder causes it to flagrate - aka "burn very rapidly". This causes huge amounts of gas to be created (which creates pressure) and when this gas is heated from the burning powder the gas volume increases creating peak pressure. And all this happens very fast. Then the bullet exits the barrel and the pressure and temperature drop back to normal. (of course it takes longer for the heat to dissipate than the pressure)
However, my friends, all the powder is burned up almost immediately (aka - in the first couple inches of bullet travel). What you see in the snow are the by-products of combustion. But it sure isn't unburned powder. (talking rifles here, not revolvers)
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Ummm.. thanks for that Captain Obvious!;)


What we are in disagreement with is whether varget is actually all burned within the first 3" (as Andy believes?) of the barrel in a .223.
I don't think it is. If it was, it would mean that all of the gas that powder was capable of producing in that load was created within that first 3" of the bullet traveling down the barrel.
 
Andy said:
I'll try once more, and spell it out more clearly and undo the words you tried to put in my mouth.
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'put words in your mouth'? wtf? I quoted what you said and asked for clarification that is what you meant. You know, that crazy little '?' is a querry right?

Andy said:
Pointless for you I'm sure as you will cling to what you said, but others might benefit.
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Wow, little sensitive are we? I think you misinterpret my posts in this thread and simply being confrontational. They are not. I'm simply here to discuss (perhaps lively) the theories of why stuffing one more grain of varget in the case isn't doing a bit of difference.

Andy said:
When did I talk about volume of gas? Heat produces the pressure.
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I'm confused by this.
As mentioned by 'Bigbubba' the primary purpose of burning powder is to convert energy. Powder burn creates volumes of gas which is translated to pressure applied to the bullet. Heat is the byproduct of this conversion of energy.

Andy said:
Pressure is decreasing, but volume is increasing and will continue to increase until the pressure level lowers to atmospheric pressure. That would likely take several feet of barrel to occur, but eventually the gains turn into losses due to bullet-bore friction - tests have shown that's usually at about 40". You will again misinterpet this.
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'Misinterpet' - I simply fail to understand completely your thoughts on this.
Atmospheric pressures are not achieved until the bullet exits the barrel - my understanding.
Peak pressure is not indicitive of complete powder burn - again my understanding.
Also, all powders will vary slightly their burn rate with different calibers (ie. the burn rate of Varget in .223 is not necessarily the same in .308) -this comes by way of the powder manufacturers and their Engineers.
Most powders do not ignite 'all at once' - ie different burn rates. These burn rates are optimised for different volumes of gas required (cartridge size and shapes), different calibers (bore diameter and weight of projectile) and yes, even barrel lengths (you are equally unlikely to come across a 6" 50 BMG barrel as you are a 30" 9mm barrel). I'm betting if one tried to fire off a 50 BMG cartridge out of a 6" barrel, you'd get a big bejebus flame and a whole crap load of unburnt powder. (obviously an exagerated example)

Andy said:
Of course a 10" barrel will produce lower MV than a 24", regardless of the powder.
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I'm not convinced of this, and I don't think it is as simple as that.
Compare that statement if you are considering 45 auto and the different powders that can be used with that cartridge.

Andy said:
Many tests have been done where barrels were cut and a variety of powders used, and it always showed that at equal pressures, more of a slower powder always produce higher MV's than less of a faster powder, regardless of barrel length. Here's where practice agrees with theory..
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I'd like to know where I can find those tests, because as I understand things powder burn rates should be tuned to the ammo (caliber), the bullet, and barrel (to a lesser degree).

Andy said:
What powder manufacturer provides multiple tables for different barrel lengths for the same round? "Use this powder with these barrel lengths only" Show me.
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Generally they don't, but in some instances they do provide differing load data for the same caliber, bullet and powders.
Case in point the .223 load data for both rifle and pistol in the Hornady manual.
While there is not a lot of changes to the barrel length ( a 26" rem. 700 v. 14" T/C Contender) the load data is different.
 
- powder choice is based on cartridge capacity, bore size and bullet weight, not barrel length (even to a lesser degree)
- the powder giving the highest MV in a long barrel will do the same in a shorter barrel and vice-versa
- the rate of acceleration of a bullet increases as pressure increases, then decreases after its peak (2-3" from the boltface), but it's still accelerating until the bullet-bore friction equals the force exeted against it, and then the bullet will start to slow until it either exits the barrel of stops in the barrel. That distance varies of course by round and the pressure you are pushing it at. For the 22LR, it's generally in the 26" range, while for a 223 operating in a "normal" pressure range (e.g. 40K+), the distance is longer than anyone would have on their gun.

Sources? several issues of "Handloader Magazine" have stated the same thing. You will not find a view contrary to mine in a reputable publication - show us one and we'll discuss. There are many "Internet Opinons" and they might not mean anything, but pose that question over on the "Accurate Reloading Forum" and you will quickly get the same opinion as I presented.

I'm thinking that this is an "AR" thing - seems you guys think it operates according to its own unique laws of physics.
 
Andy said:
- powder choice is based on cartridge capacity, bore size and bullet weight, not barrel length (even to a lesser degree)
- the powder giving the highest MV in a long barrel will do the same in a shorter barrel and vice-versa
Click to expand...

Both of these statements, foundational to your argument, are simply incorrect.

I base this on personal experience with 9mm, 115gr, in short barrels and 16+" barrels. In short barrels, HS6 is a dog. In long barrels, it shines, because it has more time to burn. Testing with powders ranging from speedy (titegroup) to slow (HS6) in both barrel lengths with a chronograph shows this.

Further, the HS6 produced large quantities of unburned powder. Not just burned "ash", but recognizable powder grains, untouched, in the short barrels.

The shortest barrel I could test was a hair over 4" of course - the effect is more pronounced in very short barrels as found in US concealed-carry guns, which is why ammo makers offer 9mm and similar calibres in versions optimized for short barrels. For example: http://www.speer-ammo.com/products/short_brl.aspx
 
The fact that peak pressure occurs close to the chamber is not indicative of completely burned powder. Past the point of pressure peak, powder is still burning, but the effect on pressure is lessened due to the increasing volume of barrel that is being acted upon.
As I think someone else said, to claim that pressure in a rifle barrel is created by heat is only partly true. Most of the pressure is created by the sudden increase in volume of the powder when it converts from a solid to a gas.

Hugh
 
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